Cepheus

Cepheus constellation lies in the northern hemisphere. It is the 27th largest constellation in the night sky, occupying an area of 588 square degrees. It is located in the fourth quadrant of the northern hemisphere (NQ4) and can be seen at latitudes between +90° and -10°. The neighboring constellations are Camelopardalis, Cassiopeia, Cygnus, Draco, Lacerta, and Ursa Minor.

[http://www.constellation-guide.com/constellation-list/cepheus-constellation/]

Cepheus in the robes of a Persian king, depicted in the Atlas Coelestis of John Flamsteed (1729)

Cepheus was the mythological king of Ethiopia. He was married to Cassiopeia, an unbearably vain woman whose boastfulness caused Poseidon to send a sea monster, Cetus, to ravage the shores of Cepheus’s kingdom. Cepheus was instructed by the Oracle of Ammon to chain his daughter Andromeda to a rock in sacrifice to the monster. She was saved by the hero Perseus, who killed the monster and claimed Andromeda for his bride. In the sky, the long-suffering Cepheus stands next to Cassiopeia, his feet extending almost to the north celestial pole. Each night he circles the pole, and as seen from Greek latitudes would have plunged head first into the sea at the lowest point, suffering the same unceremonious dunking as his vainglorious wife.

[http://www.ianridpath.com/startales/cepheus.htm]

In traditional Chinese uranography Cepheus lies across one of the quadrants symbolized by the The Black Tortoise of the North (Běi Fāng Xuán Wǔ), and Three Enclosures (Sān Yuán), that divide the sky. The name of the western constellation in modern Chinese is (xiān wáng zuò), meaning ‘the immortal king constellation.’

[https://en.wikipedia.org/wiki/Cepheus_(Chinese_astronomy)]

Cepheus, Cassiopeia and Andromeda (M31)

[http://point-of-no-23.livejournal.com/1054940.html]

Cepheus - March 1, 10:00 PM - Latitude 55° North, Longitude 95° West

[http://www.peoplesguidetothecosmos.com/constellations/cepheus.htm]

Alderamin

[https://heaven-on-earth.co.uk/project/alderamin/]

Alpha Cephei is a second magnitude star in the constellation of Cepheus near the northern pole. It has the traditional name Alderamin, an Arabic name meaning ‘the right arm.’

With a declination in excess of 62 degrees north, Alderamin is mostly visible to observers in the northern hemisphere, though the star is still visible to latitudes as far south as -27°, albeit just above the horizon. The star is circumpolar throughout all of Europe, northern Asia, Canada, and American cities as far south as San Diego. Since Alderamin has an apparent magnitude of about 2.5, the star is easily observable to the naked eye, even in light-polluted cities.

Alderamin is a white Class A star, evolving off the main sequence into a subgiant, probably on its way to becoming a red giant as its hydrogen supply runs low. In 2007, the star’s apparent magnitude was recalibrated at 2.5141 along with an updated parallax of 66.50 ± 0.11 mas yielding a distance of 15 parsecs or approximately 49 light years from Earth.

Given a surface temperature of 7,740 Kelvin, stellar models yield a total luminosity for the star of about 17 times the luminosity of the Sun. Alderamin has a radius of 2.3 times the Sun’s radius and boasting a mass that is 1.74 that of the Sun. Like other stars in its class, it is slightly variable with a range in brightness of 0.06 magnitude, and is listed as a Delta Scuti variable.

Alderamin has a very high rotation speed of at least 246 km/s, completing one complete revolution in less than 12 hours, with such a rapid turnover appearing to inhibit the differentiation of chemical elements usually seen in such stars. By comparison, the Sun takes almost a month to turn on its axis. It is also known to emit an amount of X radiation similar to the Sun, which along with other indicators suggests the existence of considerable magnetic activity- something unexpected (though not at all unusual) for a fast rotator.

Alderamin is located near the precessional path traced across the celestial sphere by the Earth’s North Pole. That means that it periodically comes within 3° of being a pole star, much as Polaris is at present. This will next occur about the year 7500 AD. The north pole of Mars lies halfway between Alderamin and the star Deneb.

[https://en.wikipedia.org/wiki/Alpha_Cephei]

Errai (Gamma Cephei), artist’s impression

[http://nameexoworlds.iau.org/exoworldsvote]

Gamma Cephei is a binary star system approximately 45 light-years away in the constellation of Cepheus. The traditional Arabic name is Errai, or Alrai, meaning ‘the shepherd.’ The primary (Gamma Cephei A) is a stellar class K1III-IV orange subgiant star; it has a red dwarf companion (Gamma Cephei B). An extrasolar planet (designated Gamma Cephei Ab, later named Tadmor) is believed to be orbiting the primary.

Gamma Cephei is the naked-eye star that will succeed Polaris as the Earth’s northern pole star, due to the precession of the equinoxes. It will be closer to the northern celestial pole than Polaris around 3000 CE and will make its closest approach around 4000 CE. The ‘title’ will pass to ι Cephei sometime around 5200 CE.

Gamma Cephei has an apparent magnitude of 3.22, nearly all of which is accounted for by Gamma Cephei A. The primary is about 6.6 billion years old (based on Fe/H metallicity) and is on its first ascent off the main sequence. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.

Gamma Cephei B has a mass approximately 0.409 times that of the Sun. It is probably a red dwarf of class M4, 6.2 degrees of magnitude fainter than the primary. It is assumed to be of similar age to its primary.

Following its discovery the planet was designated Gamma Cephei Ab. Its ostensible discovery in 1988 makes it the first extrasolar planet discovered, and was based on the same radial velocity technique later used successfully by others. In July 2014 the International Astronomical Union launched a process for giving proper names to certain exoplanets. The process involved public nomination and voting for the new names. In December 2015, the IAU announced the winning name was Tadmor for this planet. It was submitted by the Syrian Astronomical Association and is the ancient Semitic name and modern Arabic name for the city of Palmyra, a (UNESCO) World Heritage Site.

The secondary star B orbits A at only 9.8 times the semi-major axis of A’s planet. Despite how compact the system is, the planet’s orbit is stable if it is coplanar with that of the binary companion.

[https://en.wikipedia.org/wiki/Gamma_Cephei]

X-ray image of Alfirk (Beta Cephei)

[http://www.daviddarling.info/encyclopedia/A/Alfirk.html]

Beta Cephei is a third magnitude star in the constellation Cepheus. It has the traditional Arabic name Alfirk, meaning ‘the flock’ (referring to a flock of sheep). Beta Cephei is the prototype of the Beta Cephei variable stars.

Like the star Epsilon Draconis in the constellation of Draco, Alfirk is visible primarily in the northern hemisphere, given its extreme northern declination of 70 degrees and 34 minutes. The star is nevertheless visible to most observers throughout the world reaching as far south as cities like Harare in Zimbabwe, Santa Cruz de la Sierra in Bolivia or other settlements north ± 19° South latitude. The star is circumpolar throughout all of Europe, northern Asia, and North American cities as far south as Guadalajara in west central Mexico. All other locations around the globe having a latitude greater than ±20° North will notice that the star is always visible in the night sky. Because Beta Cephei is a faint third magnitude star, it may be difficult to identify in most light polluted cities, though in rural locations the star should be easily observable.

Beta Cephei is a triple star comprising a spectroscopic binary with a magnitude 8 optical companion. Its magnitude varies between +3.15 and +3.21 with a period of 0.2 days.

Beta Cephei A is a blue giant star with a stellar classification B2IIIev. The suffix ‘ev’ stands for ‘Spectral emission that exhibits variability.’ This giant star has a radius that has been estimated at 9 solar radii and a mass of 12 solar masses. Like most high-mass B-class stars, β Cep is a relatively young star with an estimated age of around 50 million years old. Like the majority of giant stars, Beta Cephei A rotates slowly on its axis with a rotational velocity of 7 deg/day, a speed which takes the star approximately 51 days to make one complete revolution.

In 2007, the star’s apparent magnitude was recalibrated at 3.1438 and the star’s parallax was updated to 4.76 ± 0.30 mas yielding a distance of 210.1 parsecs (pc) or approximately 685 light years (ly) from Earth. Given a surface temperature of 26,700 Kelvin, theoretical calculations yield a total luminosity for the star of about 36,900 times that of the sun.

[https://en.wikipedia.org/wiki/Beta_Cephei]

Mu Cephei

[https://commons.wikimedia.org/wiki/File:Mu_cephei.jpg]

Mu Cephei is a red supergiant star in the constellation Cepheus, at the edge of the IC 1396 nebula. The deep red color of Mu Cephei was noted by William Herschel, who described it as “a very fine deep garnet color.” It is thus commonly known as Herschel’s ‘Garnet Star.’ Since 1943, the spectrum of this star has served as the M2 Ia standard by which other stars are classified.

Mu Cephei is visually nearly 100,000 times brighter than the Sun, with an absolute visible magnitude of Mv = −7.6. Summing radiation at all wavelengths gives a luminosity of around 280,000 times that of the sun (bolometric magnitude −8.8), making it one of the most luminous red supergiants in the Milky Way. It is also one of the largest stars known at 1,260 solar radii (or 877,000,000 km).

Mu Cephei is a variable star and the prototype of the obsolete class of the Mu Cephei variables. It is now considered to be a semiregular variable of type SRc. Its apparent brightness varies erratically between magnitude 3.4 and 5.1. Many different periods have been reported, but they are consistently near to either 860 days or 4,400 days.

Relative sizes of the planets in the Solar System and several well-known stars, including Mu Cephei.
1. Mercury < Mars < Venus < Earth
2. Earth < Neptune < Uranus < Saturn < Jupiter
3. Jupiter < Wolf 359 < Sun < Sirius
4. Sirius < Pollux < Arcturus < Aldebaran
5. Aldebaran < Rigel < Antares < Betelgeuse
6. Betelgeuse < Mu Cephei < VV Cephei A < VY Canis Majoris.

A very luminous red supergiant, Mu Cephei is likely to be the largest star visible to the naked eye, and one of the largest known. It is best seen from the northern hemisphere from August to January.

This is a runaway star with a peculiar velocity of 80.7 ± 17.7 km/s. The distance to Mu Cephei is not very well known. The Hipparcos satellite was used to measure a parallax of 0.55 ± 0.20 milliarcseconds, which corresponds to an estimated distance of 1,333- 2,857 parsecs. However, this value is close to the margin of error. A determination of the distance based upon a size comparison with Betelgeuse gives an estimate of 390 ± 140 parsecs, so it is clear that Mu Cephei is either a much larger star than Betelgeuse or much closer (and smaller and less luminous) than expected.

The star is approximately 1,300 times larger than our Sun’s solar radius, and were it placed in the Sun’s position, its radius would reach between the orbit of Jupiter and Saturn. Mu Cephei could fit over a billion Suns into its volume.

The photosphere of Mu Cephei has an estimated temperature of 3,750 K. It may be surrounded by a shell extending out to a distance at least equal to 0.33 times the star’s radius with a temperature of 2,055 ± 25 K. This outer shell appears to contain molecular gases such as CO, H2O, and SiO.

Emissions from the star suggest the presence of a wide ring of dust and water with outer radius four times that of the star. Placed in the position of our Sun, its disk would span between 6 astronomical units (within Jupiter’s orbital zone) and 12 astronomical units (beyond Saturn’s orbit).

The star is surrounded by a spherical shell of ejected material that extends outward to an angular distance of 6″ with an expansion velocity of 10 km s−1. This indicates an age of about 2,000- 3,000 years for the shell. Closer to the star, this material shows a pronounced asymmetry, which may be shaped as a torus. The star currently has a mass loss rate of 7-10 solar masses per year.

Mu Cephei is nearing death. It has begun to fuse helium into carbon, whereas a main sequence star fuses hydrogen into helium. When a supergiant star has converted elements in its core to iron, the core collapses to produce a supernova and the star is destroyed, leaving behind a vast gaseous cloud and a small, dense remnant. For a star as massive as Mu Cephei the remnant is likely to be a black hole. The most massive red super-giants will evolve back to blue super-giants or Wolf-Rayet stars before their cores collapse, and Mu Cephei appears to be massive enough for this to happen. A post-red supergiant will produce a type IIn or type II-b supernova, while a Wolf Rayet star will produce a type Ib or Ic supernova.

[https://en.wikipedia.org/wiki/Mu_Cephei]

Krüger 60 imaged in the near-infrared and in z'-band by the Robo AO telescope

[http://www.daviddarling.info/encyclopedia/K/Kruger60.html]

Kruger 60 (DO Cephei) is a binary star system located 13.15 light-years from the Sun. These red dwarf stars orbit each other every 44.6 years.

The larger, primary star is designated component A, while the secondary, smaller star is labeled component B. Component A has about 27% of the Sun’s mass and 35% of the Sun’s radius. Component B has about 18% of the Sun’s mass and 24% of the Sun’s radius. Component B is a flare star and has been given the variable star designation ‘DO Cephei.’ It is an irregular flare that typically doubles in brightness and then returns to normal over an 8-minute period.

On average, the two stars are separated by 9.5 AUs, which is roughly the average distance of Saturn from the Sun. However, their eccentric mutual orbit causes their distance to vary between 5.5 AUs at periastron, to 13.5 at apastron.

This system is orbiting through the Milky Way at a distance from the core that varies from 7- 9 kpc with an orbital eccentricity of 0.126–0.130. The closest approach to the Sun will occur in about 88,600 years when this system will come within 1.95 parsecs.

[https://en.wikipedia.org/wiki/Kruger_60]

V354 Cephei

[http://rebuild-the-universe.wikia.com/wiki/V354_Cephei]

V354 Cephei is a red supergiant variable star located within the Milky Way. It is an irregular variable located approximately 9,000 light-years away from our Sun, and is currently considered one of the largest known stars, with a radius estimate of 1,520 solar radii (1.06×109 km; 7.1 au). If it were placed in the center of the Solar System, it would extend to between the orbits of Jupiter and Saturn.

V354 Cep is too far away to have a measured parallax which would allow its distance to be determined directly. It is near the Cepheus OB1 stellar association and considered a likely member. This association is at a distance of approximately 3,500 parsecs. The luminosity, and hence the size, of V354 Cep are disputed. Estimations of the size vary between 690-1,520 solar radii. There are similar differences in the visual extinctions derived, between two and six magnitudes.

[https://en.wikipedia.org/wiki/V354_Cephei]

RW Cephei is the bright star at the left bottom

[https://jumk.de/astronomie/big-stars/rw-cephei.shtml]

RW Cephei is an orange hypergiant star in the constellation Cepheus. One of the largest stars known, RW Cephei is estimated at 1,535 solar radii (1.068×109 km; 7.14 au), which is larger than the orbit of Jupiter.

RW Cephei is also a semi-regular variable star of type SRd, meaning that it is a slowly varying yellow giant or supergiant. Its surface is subject to pulsations in temperature and luminosity. Over the past 50 to 70 years it has varied from classes G8 to M0 with no discernible pattern. Despite its variable spectral type, it has been listed as a spectral standard star for type ‘K2 0-Ia.’

The distance to RW Cephei has been estimated on the basis of its spectroscopic luminosity and is assumed to be a member of the Cepheus OB1 association at 3,500 parsecs. This is several times further than the distance implied by the Hipparcos parallax, although the apparent diameter of the star is larger than the measured parallax and variable.

The temperature intermediate between the red supergiants and yellow hypergiants, and itself varying considerably, has led to it being variously considered as a red hypergiant or yellow hypergiant.

[https://en.wikipedia.org/wiki/RW_Cephei]

VV Cep A as it appears on Celestia

VV Cephei, also known as HD 208816, is located in the constellation Cepheus, approximately 5,000 light years from Earth. It is both a B[e] star and shell star. The distance has been estimated by a variety of techniques to be around 1.5kpc, which places it within the Cepheus OB2 association.

VV Cephei is an eclipsing binary with the second longest known period. A red supergiant fills its Roche lobe when closest to a companion blue star, the latter appearing to be on the main sequence. Matter flows from the red supergiant onto the blue companion for at least part of the orbit and the hot star is obscured by a large disk of material. The supergiant primary, known as VV Cephei A, is currently recognized as one of the largest stars in the galaxy, with an estimated radius of 1,050 solar radii.

VV Cephei experiences both primary and secondary eclipses during a 20.3 year orbit. The primary eclipses totally obscure the hot secondary star and last for nearly 18 months. Secondary eclipses are so shallow that they have not been detected photometrically since the secondary obscures such a small proportion of the large cool primary star. The timing and duration of the eclipses is variable, although the exact onset is difficult to measure because it is gradual. Only Epsilon Aurigae has a longer period among eclipsing binaries.

VV Cephei also shows semiregular variations of a few tenths of a magnitude. Visual and infrared variations appear unrelated to variations at ultraviolet wavelengths. A period of 58 days has been reported in UV, while the dominant period for longer wavelengths is 118.5 days. The short wavelength variations are thought to be caused by the disc around the hot secondary, while pulsation of the red supergiant primary caused the other variations. It has been predicted that the disc surrounding the secondary would produce such brightness variability.

The spectrum of VV Cep can be resolved into two main components, originating from a cool supergiant and a hot small star surrounded by a disk. The material surrounding the hot secondary produces emission lines, including [FeII] forbidden lines, the B[e] phenomenon known from other stars surrounded by circumstellar disks. The hydrogen emission lines are double-peaked, caused by a narrow central absorption component. This is caused by seeing the disk almost edge on where it intercepts continuum radiation from the star. This is characteristic of shell stars.

The sun compared to VV Cep A

The angular diameter of VV Cephei A can be estimated using photometric methods and has been calculated at 0.00638 arcseconds. This allows a direct calculation of the actual diameter, which is in good agreement with the 1,050 solar radii derived by other methods. Analysis of the orbit and eclipses places a firm upper limit on the possible size at 1,900 solar radii. The size of the secondary is even more uncertain, since it is physically and photometrically obscured by a much larger disc several hundred solar radii across. The secondary is certainly much smaller than either the primary or the disc, and has been calculated at solar radii from the orbital solution.

The temperature of the VV Cephei stars is again uncertain, partly because there simply isn't a single temperature that can be assigned to a significantly non-spherical diffuse star orbiting a hot companion. The effective temperature generally quoted for stars is the temperature of a spherical blackbody that approximates the electromagnetic radiation output of the actual star, accounting for emission and absorption in the spectrum. VV Cephei A is fairly clearly identified as an M2 supergiant, and as such, it is given a temperature around 3,800 K. The secondary star is heavily obscured by a disk of material from the primary, and its spectrum is almost undetectable against the disc emission. Detection of some ultraviolet absorption lines narrow down the spectral type to early B and it is apparently a main-sequence star, but likely to be abnormal in several respects due to mass transfer from the supergiant. A normal star of that type would be around 10,000 times the luminosity of the Sun, 5-8 times the radius of the Sun, 15-18 times the mass of the Sun, and around 25,000K.

Although VV Cephei A is an extremely large star showing high mass loss and having some emissions lines, it is not generally considered to be a hypergiant. The emission lines are produced from the accretion disc around the hot secondary and the absolute magnitude is typical for a red supergiant.

[https://en.wikipedia.org/wiki/VV_Cephei]

Lambda Cephei

[https://it.wikipedia.org/wiki/Lambda_Cephei]

Lambda Cephei is a fifth magnitude blue supergiant star in the constellation Cepheus, one of the hottest and most luminous visible to the naked eye.

It is a hot O6.5 supergiant star at a distance of approximately 1,980 light years, whose absolute brightness around half a million times the Sun. Its radius is around 20 times that of our star, with a mass that has been estimated to be between 45 and 60 solar masses.

Lambda Cephei turns around its axis in less than three days compared to the 24.47 days that the Sun needs to complete a full rotation and seems to be single, with no companions. Its ultimate fate is to explode as a supernova leaving behind a neutron star or perhaps a black hole.

Lambda Cephei is also a runaway star that seems to have been expelled of the stellar association Cepheus OB3, that lies at 2,800 light-years, roughly 2,5 million years ago. Its motion through the interstellar medium is producing a shockwave in front of the gases that surround it and in the direction towards it moves.

[https://en.wikipedia.org/wiki/Lambda_Cephei]

L1157

L 1157 is a dark nebula in the constellation Cepheus. It was catalogued in 1962 by U.S. astronomer Beverly T. Lynds in her Catalogue of Dark Nebulae, becoming the 1157th entry in the table; hence the designation. The cloud contains an estimated 3,900 Solar masses of material. It includes protostars that are ejecting material in bipolar outflows, forming bow shocks in the surrounding ambient gas. Formamide and HCNO have been detected in these shocked regions, among other compounds.

[https://en.wikipedia.org/wiki/L1157]

Cepheus: Trunk to Bubble

Star clusters, glowing nebulae and dark dust clouds abound in Cepheus, royal constellation of the northern hemisphere. You can follow them in amazing detail across this broad skyscape, a mosaic of telescopic images spanning about 17 degrees. Beginning at the lower left, the large emission nebula is cataloged as IC 1396. Hundreds of light-years across and about 3,000 light-years distant, it contains a dark, winding, tendril-shaped feature popularly known as the Elephant’s Trunk. Near the top middle, the bright nebula with an embedded star cluster is NGC 7380. At the upper right lies NGC 7635 (the Bubble Nebula) and star cluster M52. Many of the objects highlighted have a designation from the second version of the Sharpless catalog (Sh2) and the Barnard catalog (B) of dark nebulae. Associated with star formation, the sites are telltale markers along the region’s complex of giant molecular clouds.

[http://apod.nasa.gov/apod/ap100909.html]

IC 1396 and Surrounding Star-field

Sprawling across hundreds of light-years, emission nebula IC 1396, visible on the upper right, mixes glowing cosmic gas and dark dust clouds. Stars are forming in this area, only about 3,000 light-years from Earth. This wide angle view also captures surrounding emission and absorption nebula. The red glow in IC 1396 and across the image is created by cosmic hydrogen gas recapturing electrons knocked away by energetic starlight. The dark dust clouds are dense groups of smoke-like particles common in the disks of spiral galaxies. Among the intriguing dark shapes within IC 1396, the winding Elephant’s Trunk nebula lies just right of the nebula’s center. IC 1396 lies in the high and far off constellation of Cepheus.

[http://apod.nasa.gov/apod/ap090819.html]

The Elephant’s Trunk in IC 1396

Like an illustration in a galactic Just So Story, the Elephant’s Trunk Nebula winds through the emission nebula and young star cluster complex IC 1396, in the high and far off constellation of Cepheus. Of course, this cosmic elephant’s trunk is over 20 light-years long. The false-color view was recorded through narrow band filters that transmit the light from hydrogen (in green), sulfur (in red), and oxygen (in blue) atoms in the region. The resulting composite highlights the bright swept-back ridges that outline pockets of cool interstellar dust and gas. Such embedded, dark, tendril-shaped clouds contain the raw material for star formation and hide protostars within the obscuring cosmic dust. Nearly 3,000 light-years distant, the relatively faint IC 1396 complex covers a large region on the sky, spanning about 5 degrees. This dramatic close-up covers a 1/2 degree wide field, about the size of the Full Moon.

[http://apod.nasa.gov/apod/ap071018.html]

NGC 7380 (also known as the Wizard Nebula) is an open cluster discovered by Caroline Herschel. William Herschel included his sister’s discovery in his catalog, and labelled it H VIII.77. It is also known as 142 in the 1959 Sharpless catalog (Sh2-142). This reasonably large nebula is located in Cepheus. It is extremely difficult to observe visually, usually requiring very dark skies and an O-III filter:

[https://en.wikipedia.org/wiki/NGC_7380]

The Wizard Nebula

This image of the open star cluster NGC 7380, also known as the Wizard Nebula, is a mosaic of images from the WISE mission spanning an area on the sky of about 5 times the size of the full moon. NGC 7380 is located in the constellation Cepheus about 7,000 light-years from Earth within the Milky Way Galaxy. The star cluster is embedded in a nebula, which spans some 110 light-years. The stars of NGC 7380 have emerged from this star-forming region in the last 5 million years or so, making it a relatively young cluster.

WISE, the Wide-field Infrared Survey Explorer mission, scans the entire sky in infrared light, picking up the glow of hundreds of millions of objects and producing millions of images. The mission is designed to uncover objects never seen before, including the coolest stars, the universe's most luminous galaxies and some of the darkest near-Earth asteroids and comets. Its vast catalogs will help answer fundamental questions about the origins of planets, stars and galaxies.

WISE joins two other infrared missions in space - NASA’s Spitzer Space Telescope and the Herschel Space Observatory, a European Space Agency mission. WISE is different from these missions in that it will survey the entire sky. It is designed to cast a wide net to catch all sorts of unseen cosmic treasures, including rare oddities. All four infrared detectors aboard WISE were used to make this image.

NGC 7380 was discovered by Caroline Herschel in 1787. Her brother, William Herschel, discovered infrared light in 1800.

[https://www.nasa.gov/multimedia/imagegallery/image_feature_1615.html]

NGC 7538

[SII] = Red, Hα = Green, [OIII] = Blue

Map showing location of NGC 7538

NGC 7538, near the more famous Bubble Nebula, is located in the constellation Cepheus. It is located about 9,100 light-years from Earth. It is home to the biggest yet discovered protostar which is about 300 times the size of the Solar System. It is located in the Perseus Spiral Arm of the Milky Way and is probably part of the Cassiopeia OB2 complex. It is a region of active star formation including several luminous near-IR and far-IR sources.

[https://en.wikipedia.org/wiki/NGC_7538]

S 155, also known as the Cave Nebula, Sh2-155 or Caldwell 9, is a dim and very diffuse bright nebula in the constellation Cepheus within a larger nebula complex containing emission, reflection, and dark nebulosity.

Visually it is a difficult object, but with adequate exposure, makes a striking image. The nebula gets its name Cave Nebula from the dark lane at the eastern side abutting the brightest curve of emission nebulosity which gives the appearance of a deep cave when seen through a telescope visually:

[https://en.wikipedia.org/wiki/S_155]

Sh2-155: The Cave Nebula

This colorful skyscape features the dusty Sharpless catalog emission region Sh2-155, the Cave Nebula. In the composite image, data taken through narrowband filters tracks the glow of ionized sulfur, hydrogen, and oxygen atoms in red, green, and blue hues. About 2,400 light-years away, the scene lies along the plane of our Milky Way Galaxy toward the royal northern constellation of Cepheus. Astronomical explorations of the region reveal that it has formed at the boundary of the massive Cepheus B molecular cloud and the hot, young stars of the Cepheus OB 3 association. The bright rim of ionized interstellar gas is energized by radiation from the hot stars, dominated by the bright star just above picture center. Radiation driven ionization fronts are likely triggering collapsing cores and new star formation within. Appropriately sized for a stellar nursery, the cosmic cave is over 10 light-years across.

[http://apod.nasa.gov/apod/ap141106.html]

The Iris Nebula, also NGC 7023 and Caldwell 4, is a bright reflection nebula and Caldwell object in the constellation Cepheus. NGC 7023 is actually the cluster within the nebula, LBN 487, and the nebula is lit by a magnitude +7 star, SAO 19158. It shines at magnitude +6.8. It is located near the Mira-type variable star T Cephei, and near the bright magnitude +3.23 variable star Beta Cephei (Alphirk):

[https://en.wikipedia.org/wiki/Iris_Nebula]

NGC 7023: The Iris Nebula

These clouds of interstellar dust and gas have blossomed 1,300 light-years away in the fertile star fields of the constellation Cepheus. Sometimes called the Iris Nebula, NGC 7023 is not the only nebula in the sky to evoke the imagery of flowers, though. Still, this deep telescopic view shows off the Iris Nebula’s range of colors and symmetries in impressive detail. Within the Iris, dusty nebular material surrounds a hot, young star. The dominant color of the brighter reflection nebula is blue, characteristic of dust grains reflecting starlight. Central filaments of the dusty clouds glow with a faint reddish photoluminesence as some dust grains effectively convert the star's invisible ultraviolet radiation to visible red light. Infrared observations indicate that this nebula may contain complex carbon molecules known as PAHs. The pretty blue petals of the Iris Nebula span about six light-years.

[http://apod.nasa.gov/apod/ap140802.html]

NGC 7129 is a reflection nebula in the constellation Cepheus. A young open cluster is responsible for illuminating the surrounding nebula. A recent survey indicates the cluster contains more than 130 stars less than 1 million years old. NGC 7129 is located just half a degree from nearby cluster NGC 7142:

[https://en.wikipedia.org/wiki/NGC_7129]

NGC 7129 and NGC 7142

This alluring telescopic image looks toward the constellation Cepheus and an intriguing visual pairing of dusty reflection nebula NGC 7129 (left) and open star cluster NGC 7142. The two appear separated by only half a degree on the sky, but they actually lie at quite different distances. In the foreground, dusty nebula NGC 7129 is about 3,000 light-years distant, while open cluster NGC 7142 is likely over 6,000 light-years away. In fact, the pervasive and clumpy foreground dust clouds in this region redden the light from NGC 7142, complicating astronomical studies of the cluster. Still, NGC 7142 is thought to be an older open star cluster, while the bright stars embedded in NGC 7129 are perhaps a million years young. The telltale reddish crescent shapes around NGC 7129 are associated with energetic jets streaming away from newborn stars. Surprisingly, despite the dust, far off background galaxies can be seen in the colorful cosmic vista.

[http://apod.nasa.gov/apod/ap070913.html]

NGC 188

NGC 188 is an open cluster in the constellation Cepheus. It was discovered by John Herschel in 1825. Unlike most open clusters that drift apart after a few million years because of the gravitational interaction of our Milky Way galaxy, NGC 188 lies far above the plane of the galaxy and is one of the most ancient of open clusters known, at approximately 6.8 billion years old. NGC 188 is very close to the North Celestial Pole, under five degrees away, and in the constellation of Cepheus at an estimated 5,000 light year distance, this puts it slightly above the Milky Way’s disc and further from the center of the galaxy than the Sun.

[https://en.wikipedia.org/wiki/NGC_188]

The Fireworks Galaxy (NGC 6946) is a spiral galaxy in which nine supernovae have been observed, more than in any other galaxy:

Facing NGC 6946

From our vantage point in the Milky Way Galaxy, we see NGC 6946 face-on. The big, beautiful spiral galaxy is located just 10 million light-years away, behind a veil of foreground dust and stars in the high and far-off constellation of Cepheus. From the core outward, the galaxy’s colors change from the yellowish light of old stars in the center to young blue star clusters and reddish star forming regions along the loose, fragmented spiral arms. NGC 6946 is also bright in infrared light and rich in gas and dust, exhibiting a high star birth and death rate. In fact, since the early 20th century at least nine supernovae, the death explosions of massive stars, were discovered in NGC 6946. Nearly 40,000 light-years across, NGC 6946 is also known as the Fireworks Galaxy. This remarkable portrait of NGC 6946 is a composite that includes image data from the 8.2 meter Subaru Telescope on Mauna Kea.

[http://apod.nasa.gov/apod/ap120109.html]

NGC 2276 (left) and NGC 2300 (right)

NGC 2276 is a spiral galaxy in the constellation Cepheus. It is at a distance of about 105 million light-years away from Earth. The galaxy has asymmetrical appearance, probably due to its interaction with the elliptical galaxy NGC 2300. In the spiral arms of NGC 2276 has been discovered an intermediate mass black hole, 50,000 more massive than the Sun, named NGC 2276-3c. The hole has produced a radio-jet, 2,000 light years long. In the galaxy have been also found another seven ultraluminous X-ray sources, and five supernovae in the last 50 years. The galaxy shows high rate of star formation that may have been triggered by a collision with a dwarf galaxy:

NGC 2276: NASA’s Chandra Finds Intriguing Member of Black Hole Family Tree An intriguing object has been found in one of the spiral arms of the galaxy NGC 2276. This source, called NGC 2276-3c, appears to be an intermediate-mass black hole. According to X-ray and radio data, NGC 2276-3c contains about 50,000 times the mass of the Sun.

A newly discovered object in the galaxy NGC 2276 may prove to be an important black hole that helps fill in the evolutionary story of these exotic objects, as described in our latest press release. The main image in this graphic contains a composite image of NGC 2766 that includes X-rays from NASA’s Chandra X-ray Observatory (pink) combined with optical data from the Hubble Space Telescope and the Digitized Sky Survey (red, green and blue). The inset is a zoom into the interesting source that lies in one of the galaxy's spiral arms. This object, called NGC 2276-3c, is seen in radio waves (red) in observations from the European Very Long Baseline Interferometry Network, or EVN.

Astronomers have combined the X-ray and radio data to determine that NGC 2766-3c is likely an intermediate-mass black hole (IMBH). As the name suggests, IMBHs are black holes that are larger than stellar-mass black holes that contain about five to thirty times the mass of the Sun, but smaller than supermassive black holes that are millions or even billions of solar masses. The researchers estimated the mass of NGC 2766-3c using a well-known relationship between how bright the source is in radio and X-rays, and the mass of the black hole. The X-ray and radio brightness were based on observations with Chandra and the EVN. They found that NGC 2276-3c contains about 50,000 times the mass of the Sun.

IMBHs are interesting to astronomers because they may be the seeds that eventually evolve into supermassive black holes. They also may be strongly influencing their environment. This latest result on NGC 2276-3c suggests that it may be suppressing the formation of new stars around it. The EVN radio data reveal an inner jet that extends about 6 light years from NGC 2276-3c. Additional observations by the NSF’s Karl Jansky Very Large Array (VLA) show large-scale radio emission extending out to over 2,000 light years away from the source.

A region along the jet extending to about 1,000 light years away from NGC 2766-3c is devoid of young stars. This might provide evidence that the jet has cleared out a cavity in the gas, preventing new stars from forming there. The VLA data also reveal a large population of stars at the edge of the radio emission from the jet. This enhanced star formation could take place either when the material swept out by the jet collides with dust and gas in between the stars in NGC 2276, or when triggered by the merger of NGC 2276 with a dwarf galaxy.

In a separate study, Chandra observations of this galaxy have also been used to examine its rich population of ultra-luminous X-ray sources (ULXs). Sixteen X-ray sources are found in the deep Chandra dataset seen in this composite image, and eight of these are ULXs including NGC 2276-3c. Chandra observations show that one apparent ULX observed by ESA’s XMM-Newton is actually five separate ULXs, including NGC 2276-3c. This ULX study shows that about five to fifteen solar masses worth of stars are forming each year in NGC 2276. This high rate of star formation may have been triggered by a collision with a dwarf galaxy, supporting the merger idea for the IMBH’s origin.

Distance Estimate: About 100 million light years.

[http://chandra.harvard.edu/photo/2015/ngc2276/index.html]

[https://www.reddit.com/r/science/comments/2x58e4/black_hole_breaks_records_swallows_up_scientific/?limit=500]

Artist’s impression of a hyperluminous quasar similar to S5 0014+81 surrounded by a thick accretion disc with two powerful jets.

S5 0014+81 is a distant, compact, hyperluminous, broad-absorption line quasar or blazar located near the high declination region of the constellation Cepheus, near the North Equatorial Pole.

The object is a blazar, in fact an FSRQ quasar, the most energetic subclass of objects known as active galactic nuclei, produced by the rapid accretion of matter by a central supermassive black hole, changing the gravitational energy to light energy that can be visible in cosmic distances. In the case of S5 0014+81 it is one of the most luminous quasars known, powering up light equivalent to over 1041 watts, equal to an absolute bolometric magnitude of -31.5. If the quasar were at a distance of 280 light-years from earth it would give as much energy per square meter as the Sun despite being 18 million times more distant. The quasar’s luminosity is therefore about 300 trillion times the Sun, or over 25 thousand times as luminous as all the 100 to 400 billion stars of the Milky Way Galaxy combined, making it one of the most powerful objects in the universe. However, because of its huge distance of 12.1 billion light-years it can only be studied by spectroscopy. The host galaxy of S5 0014+81 is a giant elliptical starburst galaxy, with the apparent magnitude of 24.

The central black hole of the quasar devours an extremely huge amount of matter, equivalent to 4000 solar masses of material every year. In 2009, a team of astronomers using the Swift Spacecraft used the luminosity output of S5 0014+81 to measure the mass of the central black hole. To their surprise, they found out that the central black hole of S5 0014+81 is actually 10,000 times more massive than the black hole at the center of our galaxy, or equivalent to 40 billion solar masses. This makes it one of the most massive black holes ever discovered, more than six times the value of the black hole of M87, which was thought to be the largest black hole for almost 60 years, and was coined to be an ‘ultra-massive’ black hole. The Schwarzschild radius of this black hole is 118.35 billion kilometers. So, this black hole has an external horizon showing a diameter of 236.7 billion kilometers, 1,600 astronomical units, or 47 times the distance from the Sun to Pluto, and shows a mass equivalent to four Large Magellanic Clouds. What is even more astounding is that the monstrous black hole exists so early in the universe, at only 1.6 billion years after the Big Bang. This suggests that supermassive black holes grow up very quickly.

[https://en.wikipedia.org/wiki/S5_0014%2B81]

[https://en.wikipedia.org/wiki/Cepheus_%28constellation%29]

[Return to the 88 Modern Constellations]

Centaurus

Centaurus constellation is located in the southern hemisphere. It is one of the largest constellations in the sky. It represents the centaur, the half man- half horse creature in Greek mythology. It is the ninth largest constellation in the sky, occupying an area of 1060 square degrees. It lies in the third quadrant of the southern hemisphere (SQ3) and can be seen at latitudes between +25° and -90°. The neighboring constellations are Antlia, Carina, Circinus, Crux, Hydra, Libra, Lupus, Musca, and Vela.

[http://www.constellation-guide.com/constellation-list/centaurus-constellation/]

Johannes Hevelius’ Centaurus from Uranographia (1690)

[http://chandra.harvard.edu/photo/constellations/centaurus.html]

The figure of Centaurus can be traced back to a Babylonian constellation known as the Bison-man (MUL.GUD.ALIM). This being was depicted in two major forms: firstly, as a 4-legged bison with a human head, and secondly, as a being with a man’s head and torso attached to the rear legs and tail of a bull or bison. It has been closely associated with the Sun god Utu-Shamash from very early times.

The Greeks depicted the constellation as a centaur and gave it its current name. It was mentioned by Eudoxus in the 4th century BCE and Aratus in the 3rd century BCE. In the 2nd century AD, Claudius Ptolemy catalogued 37 stars in Centaurus. Large as it is now, in earlier times it was even larger, as the constellation Lupus was treated as an asterism within Centaurus, portrayed in illustrations as an unspecified animal either in the centaur’s grasp or impaled on its spear. The Southern Cross, which is now regarded as a separate constellation, was treated by the ancients as a mere asterism formed of the stars composing the centaur’s legs. Additionally, what is now the minor constellation Circinus was treated as undefined stars under the centaur's front hooves.

According to the Roman poet Ovid, the constellation honors the centaur Chiron, who was tutor to many of the earlier Greek heroes including Heracles (Hercules), Theseus, and Jason, the leader of the Argonauts. However, most authorities consider Sagittarius to be the civilized Chiron, while Centaurus represents a more uncouth member of the species. The legend associated with Chiron says that he was accidentally poisoned with an arrow shot by Hercules, and was subsequently placed in the heavens.

In Chinese astronomy, the stars of Centaurus are found in three areas: the Azure Dragon of the East (Dōng Fāng Qīng Lóng), the Vermillion Bird of the South (Nán Fāng Zhū Què), and the Southern Asterisms (Jìnnánjíxīngōu). Not all of the stars of Centaurus can be seen from China, and the unseen stars were classified among the Southern Asterisms by Xu Guangqi, based on his study of western star charts. However, most of the brightest stars of Centaurus, including α Cen, θ Cen, ε Cen and η Cen, can be seen in the Chinese sky.

Some Polynesian peoples considered the stars of Centaurus to be a constellation as well. On Pukapuka, Centaurus had two names: Na Mata-o-te-tokolua and Na Lua-mata-o-Wua-ma-Velo. In Tonga, the constellation was called by four different names: O-nga-tangata, Tautanga-ufi, Mamangi-Halahu, and Mau-kuo-mau. Alpha and Beta Centauri were not named specifically by the people of Pukapuka or Tonga, but they were named by the people of Hawaii and the Tuamotus. In Hawaii, the name for Alpha Centauri was either Melemele or Ka Maile-hope and the name for Beta Centauri was either Polapola or Ka Maile-mua. In the Tuamotu islands, Alpha was called Na Kuhi and Beta was called Tere.

[http://www.peoplesguidetothecosmos.com/constellations/centaurus.htm]

[http://astropixels.com/constellations/charts/Cen.html]

Alpha and Beta Centauri, also known as ‘the Pointers’, are visible all year round from the Southern Hemisphere, as the constellation they point to is Crux (the Southern Cross). 

[https://heartstar.org/2015/01/26/alpha-centauri-the-pink-star/]

Alpha Centauri: The Closest Star System

The closest star system to the Sun is the Alpha Centauri system. Of the three stars in the system, the dimmest- called Proxima Centauri- is actually the nearest star. The bright stars Alpha Centauri A and B form a close binary as they are separated by only 23 times the Earth- Sun distance- slightly greater than the distance between Uranus and the Sun. In the above picture, the brightness of the stars overwhelm the photograph causing an illusion of great size, even though the stars are really just small points of light. The Alpha Centauri system is not visible in much of the northern hemisphere. Alpha Centauri A, also known as Rigil Kentaurus, is the brightest star in the constellation of Centaurus and is the fourth brightest star in the night sky. Sirius is the brightest even though it is more than twice as far away. By an exciting coincidence, Alpha Centauri A is the same type of star as our Sun, causing many to speculate that it might contain planets that harbor life.

[http://apod.nasa.gov/apod/ap110703.html]

The two bright stars are (left) Alpha Centauri and (right) Beta Centauri. The faint red star in the center of the red circle is Proxima Centauri.

Alpha Centauri is the closest star system to the Solar System at a distance of 4.37 light-years (1.34 pc). The traditional name is Rigil Kent, a Romanization of the Arabic name ‘Rijl Qanṭūris,’ meaning ‘Foot of the Centaur.’ It is the brightest star in the constellation of Centaurus. At −0.27 apparent visual magnitude (calculated from A and B magnitudes), it is fainter only than Sirius and Canopus. The next-brightest star in the night sky is Arcturus. Alpha Centauri is a multiple-star system, with its two main stars being Alpha Centauri A (α Cen A) and Alpha Centauri B (α Cen B), usually defined to identify them as the different components of the binary α Cen AB. A third companion- Proxima Centauri (or Proxima or α Cen C)- has a distance much greater than the observed separation between stars A and B and is probably gravitationally associated with the AB system. As viewed from Earth, it is located at an angular separation of 2.2° from the two main stars. Proxima Centauri would appear to the naked eye as a separate star from α Cen AB if it were bright enough to be seen without a telescope. Alpha Centauri AB and Proxima Centauri form a visual double star. Direct evidence that Proxima Centauri has an elliptical orbit typical of binary stars has yet to be found. Together all three components make a triple star system, referred to by double-star observers as the triple star (or multiple star), α Cen AB-C.

Alpha Centauri A is the principal member, or primary, of the binary system, being slightly larger and more luminous than the Sun. It is a solar-like main-sequence star with a similar yellowish color, whose stellar classification is spectral type G2V. From the determined mutual orbital parameters, Alpha Centauri A is about 10% more massive than the Sun, with a radius about 23% larger. The projected rotational velocity of this star is 2.7 ± 0.7 km·s−1, resulting in an estimated rotational period of 22 days, which gives it a slightly faster rotational period than the Sun’s 25 days. When considered among the individual brightest stars in the sky (excluding the Sun), Alpha Centauri A is the fourth brightest at an apparent visual magnitude of +0.01, being fractionally fainter than Arcturus at an apparent visual magnitude of −0.04.

Alpha Centauri B is the companion star, or secondary, of the binary system, and is slightly smaller and less luminous than the Sun. It is a main-sequence star of spectral type K1V, making it more an orange color than the primary star. Alpha Centauri B is about 90% the mass of the Sun and 14% smaller in radius. The projected rotational velocity is 1.1 ± 0.8 km·s−1, resulting in an estimated rotational period of 41 days. Although it has a lower luminosity than component A, star B emits more energy in the X-ray band. Alpha Centauri B at an apparent visual magnitude of 1.33 would be twenty-first in brightness if it could be seen independently of Alpha Centauri A.

Together with Proxima Centauri, the bright visible components of the binary star system are called Alpha Centauri AB (α Cen AB). This ‘AB’ designation denotes the apparent gravitational center of the main binary system relative to other companion star(s) in any multiple star system. ‘AB-C’ refers to the orbit of Proxima around the central binary, being the distance between the center of gravity and the outlying companion. Because the distance between the Sun and Alpha Centauri AB does not differ significantly from either star, gravitationally this binary system is considered as if it were one object.

Asteroseismic studies, chromospheric activity, and stellar rotation (gyrochronology), are all consistent with the α Cen system being similar in age to, or slightly older than, the Sun, with typical ages quoted between 4.5 and 7 billion years (Gyr).

The relative sizes and colors of stars in the Alpha Centauri system, compared to the Sun

The two Alpha Centauri AB binary stars are too close together to be resolved by the naked eye, because the angular separation varies between 2 and 22 arcsec, but through much of the orbit, both are easily resolved in binoculars or small 5 cm (2 in) telescopes.

In the southern hemisphere, Alpha Centauri forms the outer star of The Pointers or The Southern Pointers, so called because the line through Beta Centauri (Hadar/Agena), some 4.5° west, points directly to the constellation Crux- the Southern Cross. The Pointers easily distinguish the true Southern Cross from the fainter asterism known as the False Cross.

South of about 29° S latitude, Alpha Centauri is circumpolar and never sets below the horizon. Both stars, including Crux, are too far south to be visible for mid-latitude northern observers. Below about 29° N latitude to the equator (roughly Hermosillo, Chihuahua City in Mexico, Galveston, Texas, Ocala, Florida and Lanzarote, the Canary Islands of Spain) during the northern summer, Alpha Centauri lies close to the southern horizon. The star culminates each year at midnight on 24 April or 9 p.m. on 8 June.

As seen from Earth, Proxima Centauri lies 2.2° southwest from Alpha Centauri AB. This is about four times the angular diameter of the Full Moon, and almost exactly half the distance between Alpha Centauri AB and Beta Centauri. Proxima usually appears as a deep-red star of an apparent visual magnitude of 13.1 in a sparsely populated star field, requiring moderately sized telescopes to see, but this UV Ceti-type flare star can unexpectedly brighten rapidly by as much as 0.6 magnitudes at visual wavelengths, then fade after only a few minutes. Some amateur and professional astronomers regularly monitor for outbursts using either optical or radio telescopes.

Apparent and true orbits of Alpha Centauri. The A component is held stationary and the relative orbital motion of the B component is shown. The apparent orbit (thin ellipse) is the shape of the orbit as seen by an observer on Earth. The true orbit is the shape of the orbit viewed perpendicular to the plane of the orbital motion. According to the radial velocity vs. time the radial separation of A and B along the line of sight had reached a maximum in 2007 with B being behind A. The orbit is divided here into 80 points, each step refers to a timestep of approx. 0.99888 years or 364.84 days.

With the orbital period of 79.91 years, the A and B components of this binary star can approach each other to 11.2 astronomical units, equivalent to 1.67 billion km or about the mean distance between the Sun and Saturn, or may recede as far as 35.6 AU (5.3 billion km- approximately the distance from the Sun to Pluto). This is a consequence of the binary’s moderate orbital eccentricity e = 0.5179. From the orbital elements, the total mass of both stars is about twice that of the Sun. The average individual stellar masses are 1.09 and 0.90 solar masses, respectively, though slightly higher masses have been quoted in recent years. Alpha Centauri A and B have absolute magnitudes of +4.38 and +5.71, respectively. Stellar evolution theory implies both stars are slightly older than the Sun at 5 to 6 billion years, as derived by both mass and their spectral characteristics.

Viewed from Earth, the apparent orbit of this binary star means that its separation and position angle are in continuous change throughout its projected orbit. The closest approach in the future will be in February 2016, while the widest separation occurred during February 1976 and the next will be in January 2056. In the true orbit, closest approach or periastron was in August 1955, and next in May 2035. Furthest orbital separation at apastron last occurred in May 1995 and the next will be in 2075. The apparent distance between the two stars is rapidly decreasing, at least until 2019.

Relative positions of Sun, Alpha Centauri AB and Proxima Centauri. Gray dot is projection of Proxima Centauri, located at the same distance as Alpha Centauri AB.

Hubble’s New Shot of Proxima Centauri, our Nearest Neighbor

Shining brightly in this Hubble image is our closest stellar neighbor: Proxima Centauri, just over four light-years from Earth. Although it looks bright through the eye of Hubble, as you might expect from the nearest star to the Solar System, Proxima Centauri is not visible to the naked eye. Its average luminosity is very low, and it is quite small compared to other stars, at only about an eighth of the mass of the sun. However, on occasion, its brightness increases. Proxima is what is known as a ‘flare star,’ meaning that convection processes within the star’s body make it prone to random and dramatic changes in brightness. The convection processes not only trigger brilliant bursts of starlight but, combined with other factors, mean that Proxima Centauri is in for a very long life. Astronomers predict that this star will remain middle-aged- or a ‘main sequence’ star in astronomical terms- for another four trillion years, some 300 times the age of the current Universe.

[https://www.nasa.gov/content/goddard/hubbles-new-shot-of-proxima-centauri-our-nearest-neighbor/#.V0Yt5r4rRWA]

The much fainter red dwarf Proxima Centauri, or simply Proxima, is about 15,000 AU away from Alpha Centauri AB. This is equivalent to 0.24 light years or about 5% the distance between Alpha Centauri AB and the Sun. Proxima is likely gravitationally bound to Alpha Centauri AB, orbiting it with a period between 100,000 and 500,000 years. However, it is also possible that Proxima is not gravitationally bound and thus moving along a hyperbolic trajectory with respect to Alpha Centauri AB. Theoretically, Proxima could leave the system after several million years.

Alpha Centauri C is a red dwarf of spectral class M6Ve, a small main-sequence star (Type V) with an absolute magnitude of +15.60. Its B−V color index is +1.82 and its mass is about 0.123 solar masses, or 129 Jupiter masses.

Stars closest to the Sun, including Alpha Centauri (25 April 2014)

As the stars of Alpha Centauri approach the Solar System, the measured proper motion and trigonometric parallax slowly increase. Changes are also observed in the size of the semi-major axis of the orbital ellipse, increasing by 0.03 arcsec per century. This small effect is gradually decreasing until the star system is at its closest to us, and is then reversed as the distance increases again. Consequently, the observed position angles of the stars are subject to changes in the orbital elements over time.

Based on these observed proper motions and radial velocities, Alpha Centauri will continue to gradually brighten, passing just north of the Southern Cross or Crux, before moving northwest and up towards the celestial equator and away from the galactic plane. By about 29,700 AD, in the present-day constellation of Hydra, Alpha Centauri will be 1.00 pc or 3.26 ly away. Then it will reach the stationary radial velocity of 0.0 km/s and the maximum apparent magnitude of −0.86v (which is comparable to present-day magnitude of Canopus). However, even during the time of this nearest approach, the apparent magnitude of Alpha Centauri will still not surpass that of Sirius (which will brighten incrementally over the next 60,000 years, and will continue to be the brightest star as seen from Earth for the next 210,000 years).

The Alpha Centauri system will then begin to move away from the Solar System, showing a positive radial velocity. Due to visual perspective, about 100,000 years from now, these stars will reach a final vanishing point and slowly disappear among the countless stars of the Milky Way. Here this once bright yellow star will fall below naked-eye visibility somewhere in the faint present day southern constellation of Telescopium.

In about 4000 years, the proper motion of Alpha Centauri will mean that from the point of view of Earth it will appear close enough to Beta Centauri to form an optical double star. Beta Centauri is in reality far more distant than Alpha Centauri.

In 2012, a planet around Alpha Centauri B was announced, but in 2015 a new analysis concluded that it almost certainly does not exist and was just a spurious artifact of the data analysis. On 25 March 2015, a scientific paper published transit results for Alpha Centauri B using the Hubble Space Telescope for a total of 40 hours. It evidenced a transit event possibly corresponding to a planetary body. This planet would most likely orbit Alpha Centauri B with an orbital period of 20.4 days or less. If confirmed, this planet would be called Alpha Centauri Bc. Like the probably spurious Alpha Centauri Bb, it would be far too close to Alpha Centauri B to harbour life.

The discovery of planets orbiting other star systems, including similar binary systems (Gamma Cephei), raises the possibility that additional planets may exist in the Alpha Centauri system. Such planets could orbit Alpha Centauri A or Alpha Centauri B individually, or be on large orbits around the binary Alpha Centauri AB. Because both the principal stars are fairly similar to the Sun, astronomers have been especially interested in making detailed searches for planets in the Alpha Centauri system. Several established planet-hunting teams have used various radial velocity or star transit methods in their searches around these two bright stars.

Looking toward the sky around Orion from Alpha Centauri, with Sirius near Betelgeuse, Procyon in Gemini, and the Sun between Perseus and Cassiopeia.

Viewed from near the Alpha Centauri system, the sky would appear very much as it does for an observer on Earth, except that Centaurus would be missing its brightest star. The Sun would be a yellow star of an apparent visual magnitude of +0.5 in eastern Cassiopeia, at the antipodal point of Alpha Centauri’s current right ascension and declination. This place is close to the 3.4-magnitude star ε Cassiopeiae. An interstellar or alien observer would find the ‘W’ of Cassiopeia had become a ‘/\/\/’ shape nearly in front of the Heart Nebula in Cassiopeia. Sirius lies less than a degree from Betelgeuse in the otherwise unmodified Orion and is with −1.2 a little fainter than from Earth but still the brightest star in the Alpha Centauri sky. Procyon is also displaced into the middle of Gemini, outshining Pollux, whereas both Vega and Altair are shifted northwestward relative to Deneb (which barely moves, due to its great distance), giving the Summer Triangle a more equilateral appearance.

From Proxima itself, Alpha Centauri AB would appear like two close bright stars with the combined apparent magnitude of −6.8. Depending on the binary’s orbital position, the bright stars would appear noticeably divisible to the naked eye, or occasionally, but briefly, as single unresolved star. Based on the calculated absolute magnitudes, the visual apparent magnitudes of Alpha Centauri A and B would be −6.5 and −5.2, respectively.

View from Next Door

This artist’s impression shows the planet orbiting the star Alpha Centauri B, a member of the triple star system that is the closest to Earth. Alpha Centauri B is the most brilliant object in the sky and the other dazzling object is Alpha Centauri A. Our own Sun is visible to the upper right. The tiny signal of the planet was found with the HARPS spectrograph on the 3.6-metre telescope at ESO’s La Silla Observatory in Chile.

[https://www.eso.org/public/usa/images/eso1241b/]

An observer on a hypothetical planet orbiting around either Alpha Centauri A or Alpha Centauri B would see the other star of the binary system as an intensely bright object in the night sky, showing a small but discernible disk while near periapse: A up to 210 arc seconds, B up to 155 arc seconds. Near apoapse, the disc would shrink to 60 arc seconds for A, 43 arc seconds for B, being too small to resolve by naked eye. In any case, the dazzling surface brightness could make the discs harder to resolve than a similarly sized less bright object.

For example, some theoretical planet orbiting about 1.25 AU from Alpha Centauri A (so that the star appears roughly as bright as the Sun viewed from the Earth) would see Alpha Centauri B orbit the entire sky once roughly every one year and three months, the planet’s own orbital period. Added to this would be the changing apparent position of Alpha Centauri B during its long eighty-year elliptical orbit with respect to Alpha Centauri A. (The average speed, at 4,5 degrees per Earth year, is comparable in speed to Uranus here. With the eccentricity of the orbit, the maximum speed near periapse, about 18 degrees per Earth year, is faster than Saturn, but slower than Jupiter. The minimum speed near apoapse, about 1,8 degrees per Earth year, is slower than Neptune.) Depending on its and planet’s position on their respective orbits, Alpha Centauri B would vary in apparent magnitude between −18.2 (dimmest) and −21.0 (brightest). These visual apparent magnitudes are much dimmer than the apparent magnitude of the Sun as viewed from the Earth (−26.7). The difference of 5.7 to 8.6 magnitudes means Alpha Centauri B would appear, on a linear scale, 2500 to 190 times dimmer than Alpha Centauri A (or the Sun viewed from the Earth), but also 190 to 2500 times brighter than the full Moon as seen from the Earth (−12.5).

Also, if another similar planet orbited at 0.71 AU from Alpha Centauri B (so that in turn Alpha Centauri B appeared as bright as the Sun seen from the Earth), this hypothetical planet would receive slightly more light from the more luminous Alpha Centauri A, which would shine 4.7 to 7.3 magnitudes dimmer than Alpha Centauri B (or the Sun seen from the Earth), ranging in apparent magnitude between −19.4 (dimmest) and −22.1 (brightest). Thus Alpha Centauri A would appear between 830 and 70 times dimmer than the Sun but some 580 to 6900 times brighter than the full Moon. During such planet’s orbital period of 0.6 years, an observer on the planet would see this intensely bright companion star circle the sky just as we see with the Solar System’s planets. Furthermore, Alpha Centauri A’s sidereal period of approximately eighty years means that this star would move through the local ecliptic as slowly as Uranus with its eighty-four year period, but as the orbit of Alpha Centauri A is more elliptical, its apparent magnitude will be far more variable. Although intensely bright to the eye, the overall illumination would not significantly affect climate nor influence normal plant photosynthesis.

Assuming this hypothetical planet had a low orbital inclination with respect to the mutual orbit of Alpha Centauri A and B, then the secondary star would start beside the primary at ‘stellar’ conjunction. Half the period later, at ‘stellar’ opposition, both stars would be opposite each other in the sky. Then, for about half the planetary year the appearance of the night sky would be a darker blue- similar to the sky during totality at any total solar eclipse. Humans could easily walk around and clearly see the surrounding terrain, and reading a book would be quite possible without any artificial light. After another half period in the stellar orbit, the stars would complete their orbital cycle and return to the next stellar conjunction, and the familiar day and night cycle would return.

Alpha Centauri is envisioned as a likely first target for manned or unmanned interstellar exploration. Crossing the huge distance between the Sun and Alpha Centauri using current spacecraft technologies would take several millennia, though the possibility of nuclear pulse propulsion or laser light sail technology could reduce the journey time to a matter of decades.

[https://en.wikipedia.org/wiki/Alpha_Centauri]

Hadar (Beta Centauri) and Rigil Kent (Alpha Centauri) are known as the Southern Pointer Stars because they point to the Southern Cross.

[http://earthsky.org/brightest-stars/beta-centauri-hadar-southern-pointer-star]

Beta Centauri is a trinary star system in the constellation of Centaurus. The system’s combined apparent visual magnitude of 0.61, makes it the second brightest star in the constellation Centaurus and the tenth brightest star in the night sky. The traditional name Hadar is related to the Arabic root ح ض ر (‎ḥ-ḍ-r), meaning ‘to be present.’ The distance to this system is about 400 light-years (120 parsecs).

All the spectral lines detected are consistent with a B1 type star, with only the line profiles varying, so it is thought that all three stars have the same spectral type. The companion is separated from the primary by 1.3 seconds of arc, and has remained so since the discovery, although the position angle has changed six degrees since. Beta Centauri B orbits the primary at 0.6 light years, or 100k AUs, with a period of roughly 1500 years. Beta Centauri B is a B1 dwarf with an apparent magnitude of 4.

Beta Centauri’s observed periodic variation in radial velocity suggested that Beta Centauri A is a double-lined spectroscopic binary. The primary consists of a pair of stars, (A1 and A2) with nearly identical mass that orbit each other over a period of 357 days with a large eccentricity of about 0.825. The pair are separated by a mean distance of roughly 4 astronomical units. Both A1 and A2 apparently have a stellar classification of B1 III, with the luminosity class of III indicating giant stars that are evolving away from the main sequence.

[https://en.wikipedia.org/wiki/Beta_Centauri]

Theta Centauri has the traditional name Menkent, possibly an abbreviation of the Arabic ‘al mankib al-qanturis,’ meaning ‘shoulder of the Centaur.’ This star has an apparent visual magnitude of +2.06, making it the fourth brightest member of the constellation. This star is close enough to the Earth that its distance can be measured using the parallax technique, yielding a value of 58.8 light-years (18.0 parsecs).

This is an evolved giant star with a stellar classification of K0 III, and with a radius of about 10.6 times the radius of the Sun. The outer envelope has an effective temperature of 4,980 K, giving it the orange-hued glow of a cool, K-type star.

[https://en.wikipedia.org/wiki/Theta_Centauri]

Gamma Centauri has the traditional name Muhlifain. It is a double star located about 130 light-years (40 parsecs) from Earth. The combined apparent visual magnitude of the pair is +2.17, although individually they are third magnitude stars. The stellar classification of the pair is A1IV+, suggesting they are A-type subgiant stars in the process of becoming giants. Individually, their stellar classifications are sometimes listed as A0III, which would mean they have already become giants.

Their orbital period is 84.5 years, with a semimajor axis of 0.93 arcseconds. At the distance of this system, this is equivalent to a linear distance of about 93 Astronomical Units. The star Tau Centauri is relatively close to Gamma Centauri, with an estimated separation of 1.72 light-years (0.53 pc).
[https://en.wikipedia.org/wiki/Gamma_Centauri]

Epsilon Centauri is a massive star with nearly 12 times the mass of the Sun, at a distance of around 430 light-years (130 parsecs) from Earth. The spectrum matches a stellar classification of B1 III, indicating this is an evolved giant star. It is radiating more than 15,000 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 24,000 K, giving it the blue-white hue of a B-type star. It is a variable star with a slightly variable apparent visual magnitude of +2.30, with a primary period of 0.16961 days (4 hours 4 minutes), completing 5.9 cycles per day. During each cycle, the brightness of the star varies from apparent magnitude +2.29 to +2.31. It is a relatively young star, with an age of around 16 million years.

[https://en.wikipedia.org/wiki/Epsilon_Centauri]

Delta Centauri is a variable star with a brightness which varies from magnitude +2.51 to +2.65. The apparent visual magnitude of this star makes it readily visible to the naked eye. It is located at a distance of about 410 light-years (130 parsecs) from the Earth.

The energy from this star is being radiated at an effective temperature of over 22,000 K from the outer envelope, giving it the blue-white hue of a B-type star. It has a radius of 5.9 times the radius of the Sun and 8.6 times the Sun’s mass. The stellar classification of this star is B2 IVne, with the luminosity class of IV indicating that this is a subgiant star that has exhausted the hydrogen at its core and begun to evolve away from the main sequence. The star is spinning rapidly, with the resulting Doppler effect giving its spectrum broad absorption lines as indicated by the ‘n.’ The suffix ‘e’ means this is a classical Be star, which is a type of hot star that has not yet evolved into a supergiant and is surrounded by circumstellar gas. The presence of this gas creates an excess emission of infrared, along with emission lines in the star’s spectrum. Most of it is concentrated around the equator, forming a disk.

Some of the variation in this star may be explained by assuming it is a binary star system. This proposed secondary star would need to have about 4- 7 times the Sun’s mass and be orbiting with a period of at least 4.6 years at a minimum separation of 6.9 Astronomical Units. Delta Centauri shares a common proper motion with the nearby stars HD 105382 and HD 105383, so they may form a small cluster or perhaps a triple star system.

[https://en.wikipedia.org/wiki/Delta_Centauri]

BPM 37093 (Diamond Star)

The interior of this probably very old white dwarf is a diamond with a diameter of more than 4000 kilometers. The inside of white dwarfs often is pure carbon. The pressure in this star has agglomerated it to form a diamond.

[https://jumk.de/astronomie/special-stars/bpm-37093.shtml]

BPM 37093 (V886 Centauri) is a variable white dwarf star of the DAV, or ZZ Ceti, type, with a hydrogen atmosphere and an unusually high mass of approximately 1.1 times the Sun’s. It is about 50 light-years from Earth, in the constellation Centaurus, and vibrates; these pulsations cause its luminosity to vary. Like other white dwarfs, BPM 37093 is thought to be composed primarily of carbon and oxygen, which are created by thermonuclear fusion of helium nuclei in the triple-alpha process.

As a white dwarf cools, its material should crystallize, starting at the center. When a star pulsates, observing its pulsations gives information about its structure. BPM 37093 was first observed to be a pulsating variable in 1992, and in 1995 it was pointed out that this yielded a potential test of the crystallization theory. It is estimated that approximately 90% of the mass of BPM 37093 had crystallized. Other estimates give a crystallized mass fraction of between 32% and 82%. Any of these estimates would result in a total crystalline mass in excess of 5×1029 kilograms.

Since a diamond also consists of crystallized carbon, the star BPM 37093 has been nicknamed Lucy after The Beatles’ hit ‘Lucy in the Sky with Diamonds.’

[https://en.wikipedia.org/wiki/BPM_37093]

The Brown Dwarf 2M1207 and its Planetary Companion

This composite image shows the first planet outside of our solar system (right) found orbiting a brown dwarf, dubbed 2M1207 (center). The fainter planetary companion is at an angular distance of 778 milliarcsec from 2M1207. The exoplanet orbits at a distance from the brown dwarf that is nearly twice as far as Neptune is from the Sun. Originally designated the Giant Planet Candidate Companion (GPCC) by its discoverers, further observations, particularly its motion in the sky relative to 2M1207, ascertained its true nature.

[https://www.eso.org/public/usa/images/eso0515a/]

2M1207 was discovered during the course of the 2MASS infrared sky survey: hence the ‘2M’ in its name, followed by its celestial coordinates. With a fairly early (for a brown dwarf) spectral type of M8, it is very young sub-stellar object. Its estimated mass is around 25 Jupiter masses. The companion, 2M1207b, is estimated to have a mass of 3- 10 Jupiter masses. Still glowing red hot, it will shrink to a size slightly smaller than Jupiter as it cools over the next few billion years. The distance of this moving cluster is estimated to 53 parsec or 172 light years.

[https://en.wikipedia.org/wiki/2M1207]

Artist’s impression of HR 5171 and its companion star

HR 5171, also known as HD 119796 and V766 Centauri, is a triple star system in the constellation Centaurus, around 12,000 light years from Earth. It contains the largest known yellow hypergiant star which is also an eclipsing binary.

The HR 5171 system contains at least three stars. The primary A is an eclipsing binary (components Aa and Ab), with two yellow stars in contact and orbiting in 1,304 days. The companion has been detected directly by optical interferometry, and is approximately one third the size of the hypergiant primary. The two stars are in the common envelope phase where material surrounding both stars rotates synchronously with the stars themselves.

Component B, 9.4" away, is a B0 supergiant. It is a highly luminous massive star in itself but 3 magnitudes fainter than the yellow hypergiant. At 3.6 kpc, this is a projected separation of 35,000 AU although the actual separation could be larger.

HR 5171 shows erratic changes in brightness and color. HR 5171B is apparently stable, with the changes being due to physical changes in the hypergiant star, variations in the envelope, and eclipses between the two close companions.

HR 5171A is the largest known yellow star. It has been calculated to be more than 1,300 times the diameter of the Sun. If HR 5171A were to be put in the center of the Solar System, it would stretch to a distance of 912,584,500 kilometres (567,053,700 mi), between the orbits of Jupiter and Saturn. It has a volume approximately 2.274 billion times bigger than the Sun.

This type of star has evolved from an initial mass of around 60 times the Sun to a cool hypergiant and is now shedding its remaining outer layers in a series of dramatic explosions, progressively increasing in temperature. It may become a blue supergiant or luminous blue variable before declining in luminosity, but may explode as a supernova before that point.

The very high luminosity, extreme size, and mass exchange with the lower mass companion make this an unusual star within a very rare class of stars.

[https://en.wikipedia.org/wiki/HR_5171]

Przybylski’s Star

The blue star HD 101065 was named after its discoverer, Antoni Przybylski. This star shows in its spectrum a very peculiar chemical composition. Commonly frequent metals like iron and nickel are scarce here, but a lot of rare metals like strontium, niobium, caesium, many lanthanoids and even uranium are highly overabundant. The reason for this is unknown. This star could either be a main sequence star or a subgiant.

[https://jumk.de/astronomie/special-stars/przybylskis-star.shtml]

Przybylski’s Star, or HD 101065, is a Rapidly oscillating star that is located at a distance of roughly 370 light-years (110 parsecs) from the Sun in the constellation of Centaurus. In 1961, the Polish-Australian astronomer Antoni Przybylski discovered that this star had a peculiar spectrum that would not fit into the standard framework for stellar classification. Przybylski’s observations indicated unusually low amounts of iron and nickel in the star’s spectrum, but higher amounts of unusual metallic elements. Przybylski’s Star also contains many different short-lived actinide elements with actinium, protactinium, neptunium, plutonium, americium, curium, berkelium, californium, and einsteinium being detected. Other radioactive elements discovered in this star include technetium and promethium.

HD 101065 is the prototype star of the roAp star class (rapidly oscillating A-type peculiar star). In 1978, it was discovered to pulsate with a period of 12.15 min. Compared to neighboring stars, HD 101065 has a high peculiar velocity of 23.8 ± 1.9 km s−1. A companion has also been detected, a 14th magnitude star (in infrared) 8 arc seconds away. This would be a separation of nearly 1,000 AU, but there is a possibility that it is an unrelated star in a chance alignment.

[https://en.wikipedia.org/wiki/Przybylski%27s_Star]

A dust ring encircles HR 4796’s primary star

HR 4796 is a binary star system in the constellation of Centaurus. It’s distance is 237 light-years (73 parsecs) from the Earth. The two components of this system have an angular separation of 7.7 arcseconds, which, at their estimated distance, is equivalent to a projected separation of about 560 Astronomical Units (AU), or 560 times the separation of the Earth from the Sun. The star and its ring resemble an eye, and it is sometimes known by the nickname ‘Sauron’s Eye.’

This is a young system with an estimated age of about 8 million years. The primary member A has a stellar classification of A0V, while its smaller companion B is a red dwarf with a classification of M2.5V. The luminosity class of ‘V’ indicates that both stars belong to the main sequence and are generating energy through the thermonuclear fusion of hydrogen at their cores. The primary is emitting this energy from its outer envelope at an effective temperature of about 9,378 K, which gives it the white hue characteristic of A-type stars. It has a radius about 168% of the radius of the Sun and 218% of the Sun’s mass. By comparison, the secondary has only 30% of a solar mass. The abundance of elements other than hydrogen or helium, what astronomers term the star’s metallicity, is similar to the proportion in the Sun.

In 1991, the primary was found to have an excess of infrared emission, implying that it has a circumstellar debris disk. Observations using the Near-Infrared Multi-Object Spectrometer aboard the Hubble Space Telescope in 2007 indicated that the dust had a reddish spectrum similar to that of tholins. The disk was resolved with the Hubble Space Telescope in 2009, confirming that it exists. Based on these images, the disk has a radius of 75 AU and a width of less than 18.5 AU. It may have some asymmetries and the center appears to be slightly offset from the star. The dust in the disk is likely the result of collisions between larger particles. In 2011, observations of the ring offset by the Subaru Telescope implies that one or more planets would likely exist within gaps tugging at its dust grains. With a new image in 2014, the configuration and alignment of the dust ring and HR4796A has been nicknamed ‘Eye of Sauron.’

The space velocity of HR 4796 suggests that it may be a member of the TW Hydrae association of stars that share a common origin. A low-mass member of this association, identified as 2MASS J12354893−3950245, may be a tertiary component of the HR 4796 system. It has a proper motion matching HR 4796, suggesting it is gravitationally bound to the other two stars, and is separated from the pair by a distance of about 13,500 AU.

[https://en.wikipedia.org/wiki/HR_4796]

Eclipsing Ring System J1407

[http://www.ctio.noao.edu/noao/content/eclipsing-ring-system-j1407]

1SWASP J140747.93-394542.6 (often abbreviated 1SWASP J140747 or J1407) is a star similar to the Sun located in the constellation of Centaurus at a distance of about 420 light years from Earth. A relatively young star, its age is estimated to be 16 million years, and its mass is about 90% that of the Sun’s. The star has an apparent magnitude of 12.3 and requires a telescope to be seen.

J1407 is probably orbited by at least one known body, 1SWASP J1407b (J1407b), thought to be either a large gas giant planet or a brown dwarf with an immense ring system. The discovery of the J1407 system and its unusual eclipses were first reported in 2012. The existence and parameters of the ring system around the sub-stellar companion J1407b were deduced from the observation of a very long and complex eclipse of the star J1407 during a 56-day period in 2007. The low-mass companion J1407b has been referred to as a ‘Saturn on steroids’ or ‘Super Saturn’ due to its massive system of circum-planetary rings with a radius of approximately 90 million km (0.6 AU). The orbital period of the ringed companion J1407b is estimated to be around a decade (constrained to 3.5 to 13.8 years), and its most probable mass is approximately 13 to 26 Jupiter masses, but with considerable uncertainty. The ring system has an estimated mass similar to that of the Earth. A gap in the ring system at about 61 million km (0.4 AU) from its center is considered to be indirect evidence of the existence of an exo-moon with mass up to 0.8 Earth masses.

From Earth’s point of view, the ring system appears about 3.7 milliarcseconds across. For comparison, if it were the same distance from our solar system Saturn’s ring system would be 0.006 milliarcseconds across.

[https://en.wikipedia.org/wiki/1SWASP_J140747.93-394542.6]

PSR B1259-63: Pulsar Punches Hole In Stellar Disk

A clump of material has been jettisoned from a double star system at incredibly high speeds. X-rays from Chandra reveal that a pulsar in orbit around a massive star punched through a circumstellar disk of material. Three Chandra observations of the system were taken between December 2011 and February 2014. The data suggest the clump may even be accelerating due to the pulsar’s powerful winds.

This trio of images contains evidence from NASA’s Chandra X-ray Observatory that a clump of stellar material has been jettisoned away from a double star system at incredibly high speeds. This system, known as PSR B1259-63/LS 2883- or B1259 for short- is comprised of two objects in orbit around one another. The first is a star about 30 times as massive as the Sun that has a disk of material swirling around it. The other is a pulsar, an ultra-dense neutron star left behind when an even more massive star underwent a supernova explosion.

Researchers think that the pulsar knocked out the chunk of debris, which spans over a hundred times the size of the Solar System, when it collided with the disk around the massive star while traveling in its elliptical orbit lasting 41 months. (An artist’s illustration shows the pulsar just after having collided with the disk.) Astronomers came to this conclusion after analyzing three separate Chandra observations taken between December 2011 and February 2014, as labeled in the three images. The bright source in the center of these images is the binary system, while the smaller point-like source to the lower right seen in the second two observations is the clump that has been dislodged.

The Chandra observations also suggest that the clump is not only moving quickly but may, in fact, be picking up speed. The average of the three observations shows the clump is moving about 7% the speed of light, but the data suggest it may have accelerated to 15% the speed of light between the second and third observations. This acceleration could be due to intense winds flowing off of the pulsar’s surface at nearly the speed of light, which are caused by its rapid rotation and strong magnetic fields.

The X-ray emission observed by Chandra is likely produced by a shock wave created as the pulsar’s wind rams into the clump of material. The ram pressure generated by this interaction could also accelerate the clump. Chandra will continue monitoring B1259 and its moving clump with observations scheduled for later this year and in 2016. Distance Estimate: About 7,500 light years.

[http://chandra.harvard.edu/photo/2015/psrb1259/index.html]

Naked Eye Nova Centauri 2013

Brightest stellar beacons of the constellation Centaurus, Alpha and Beta Centauri are easy to spot from the southern hemisphere. For now, so is new naked eye Nova Centauri 2013. In this night skyscape recorded near Las Campanas Observatory in the Chilean southern Atacama desert on December 5, the new star joins the old in the expansive constellation, seen at early morning hours through a greenish airglow. Caught by nova hunter John Seach from Australia on December 2 as it approached near naked eye brightness, Nova Cen 2013 has been spectroscopically identified as a classical nova, an interacting binary star system composed of a dense, hot white dwarf and cool, giant companion. Material from the companion star builds up as it falls onto the white dwarf’s surface triggering a thermonuclear event. The cataclysmic blast results in a drastic increase in brightness and an expanding shell of debris. The stars are not destroyed, though. Classical novae are thought to recur when the flow of material onto the white dwarf eventually resumes and produces another outburst.

[http://apod.nasa.gov/apod/ap131207.html]

The globular cluster Omega Centauri

[https://en.wikipedia.org/wiki/Omega_Centauri]

ω Centauri (NGC 5139), despite being listed as the constellation’s ‘omega’ star, is in fact a naked-eye globular cluster, located at a distance of 17,000 light-years with a diameter of 150 light-years. It is the largest and brightest globular cluster in the Milky Way, at ten times the size of the next-largest cluster; it has a magnitude of 3.7. It is also the most luminous globular cluster in the Milky Way, at over one million solar luminosities. Omega Centauri contains several million stars, most of which are yellow dwarf stars, but also possesses red giants and blue-white stars; the stars have an average age of 12 billion years. This has prompted suspicion that Omega Centauri was the core of a dwarf galaxy that had been absorbed by the Milky Way. Omega Centauri was determined to be non-stellar in 1677 by the English astronomer Edmond Halley, though it was visible as a star to the ancients. Its status as a globular cluster was determined by James Dunlop in 1827. To the unaided eye, Omega Centauri appears fuzzy and is obviously non-circular; it is approximately half a degree in diameter, the same size as the full Moon:

From Alpha to Omega in Crete

This beautiful telephoto composition spans light-years in a natural night skyscape from the island of Crete. Looking south, exposures both track the stars and record a fixed foreground in three merged panels that cover a 10x12 degree wide field of view. The May 15 waxing gibbous moonlight illuminates the church and mountainous terrain. A mere 18 thousand light-years away, huge globular star cluster Omega Centauri (NGC 5139) shining above gives a good visual impression of its appearance in binoculars on that starry night. Active galaxy Centaurus A (NGC 5128) is near the top of the frame, some 11 million light-years distant. Also found toward the expansive southern constellation Centaurus and about the size of our own Milky Way is edge on spiral galaxy NGC 4945. About 13 million light-years distant it’s only a little farther along, and just above the horizon at the right.

[http://apod.nasa.gov/apod/ap160629.html]

NGC 3918 is a bright planetary nebula in the constellation Centaurus, which is called the ‘Blue Planetary’ or ‘The Southerner.’ It is the brightest of the far southern planetary nebulae. This nebula was discovered by Sir John Herschel in March 1834, and is easily visible through small telescopes. Distance is estimated 1.5 kpc:

[https://en.wikipedia.org/wiki/NGC_3918]

Planetary Nebula NGC 3918

Studying images of proto-planetary nebulae is important to understanding the process of star death. A star begins to die when it has exhausted its thermonuclear fuel - hydrogen and helium. The star then becomes bright and cool (red giant phase) and swells to several tens of times its normal size. It begins puffing thin shells of gas off into space. These shells become the star's cocoon. In the Hubble images, the shells are the concentric rings seen around each nebula.

[https://www.spacetelescope.org/images/opo9811i/]

The Boomerang Nebula is a protoplanetary nebula in the constellation Centaurus. It is also known as the Bow Tie Nebula. The nebula’s temperature is measured at 1 K (−272.15 °C or −457.87 °F), making it the coolest natural place currently known in the Universe:

[https://en.wikipedia.org/wiki/Boomerang_Nebula]

Boomerang Nebula

The Hubble Space Telescope has ‘caught’ the Boomerang Nebula in these new images taken with the Advanced Camera for Surveys. This reflecting cloud of dust and gas has two nearly symmetric lobes (or cones) of matter that are being ejected from a central star. Over the last 1,500 years, nearly one and a half times the mass of our Sun has been lost by the central star of the Boomerang Nebula in an ejection process known as a bipolar outflow. The nebula’s name is derived from its symmetric structure as seen from ground-based telescopes. Hubble’s sharp view is able to resolve patterns and ripples in the nebula very close to the central star that are not visible from the ground. The Boomerang Nebula is about 5,000 light-years from Earth in the direction of the Southern constellation Centaurus. Measurements show the nebula has a temperature of only one degree Kelvin above absolute zero (nearly -460 degrees Fahrenheit).

[https://www.nasa.gov/multimedia/imagegallery/image_feature_405.html]

RCW 49 is a H II region nebula. It is a dusty stellar nursery that contains more than 2,200 stars:

[https://en.wikipedia.org/wiki/RCW_49]

Cosmic Construction Zone RCW 49

Stars and planets appear to be under construction in dusty nebula RCW 49. This Spitzer Space Telescope false-color infrared view of the nearby stellar nursery shows that known, hot stars are well on their way to clearing out the nebula's central regions. But it also uncovers more than 300 newborn stars, seen here strewn throughout the cosmic dust clouds and filaments. The infrared data indicate the likely presence of protoplanetary discs around some of the infant suns, among the faintest and farthest potential planet-forming discs ever observed. Such exciting results give further support to the idea that planet-forming discs are a natural part of a star’s evolution. A mere 14,000 light-years away toward the constellation Centaurus, the industrious RCW 49 is about 350 light-years across.

[http://apod.nasa.gov/apod/ap040603.html]

IC 2944, also known as the Running Chicken Nebula or the Lambda Centauri Nebula, is an open cluster with an associated emission nebula found in the constellation Centaurus, near the star Lambda Centauri:

[https://en.wikipedia.org/wiki/IC_2944]

Stars and Gas of the Running Chicken Nebula

To some, it looks like a giant chicken running across the sky. To others, it looks like a gaseous nebula where star formation takes place. Cataloged as IC 2944, the Running Chicken Nebula spans about 100 light years and lies about 6,000 light years away toward the constellation of the Centaur (Centaurus). The featured image, shown in scientifically assigned colors, was captured recently in an 11-hour exposure from a backyard near Melbourne, Australia. Two star clusters are visible: the Pearl Cluster seen on the far left, and Collinder 249 embedded in the nebula’s glowing gas. Although difficult to discern here, several dark molecular clouds with distinct shapes can be found inside the nebula.

[http://apod.nasa.gov/apod/ap160531.html]

Centaurus is rich in galaxies as well. NGC 4622 is a face-on spiral galaxy located 200 million light-years from Earth (redshift 0.0146). Its spiral arms wind in both directions, which makes it nearly impossible for astronomers to determine the rotation of the galaxy. Astronomers theorize that a collision with a smaller companion galaxy near the core of the main galaxy could have led to the unusual spiral structure:

The Spiral Arms of NGC 4622

While stirring a morning cup of coffee and thinking cosmic thoughts many astronomers would glance at this Hubble Space Telescope image of spiral galaxy NGC 4622 and assume that the galaxy was rotating counterclockwise in the picture. One hundred million light-years away in the constellation Centaurus, NGC 4622’s gorgeous outer spiral arms, traced by bright bluish star clusters and dark dust lanes, should be winding up like... well, like swirls in a cup of coffee. But a closer look at this galaxy reveals that a pronounced inner spiral arm winds in the opposite direction. So which way is this galaxy rotating? Recent evidence combining ground-based spectroscopy and the sharp Hubble image data surprisingly indicates that the galaxy is likely rotating clockwise in the picture, its outer spiral arms opening outward in the direction of rotation. There are further indications that a past collision with a smaller companion galaxy has contributed to this bizarre rotational arrangement of spiral arms, essentially unique among known large spiral galaxies, in NGC 4622.

[http://apod.nasa.gov/apod/ap020125.html]

NGC 4945 is a spiral galaxy seen edge-on from Earth. It is visible with any amateur telescope, as well as binoculars under good conditions; it has been described as ‘shaped like a candle flame,’ being long and thin (16' by 3'). In the eyepiece of a large telescope, its southeastern dust lane becomes visible:

NGC 4945 in Centaurus

Large, dusty, spiral galaxy NGC 4945 is seen edge-on near the center of this rich telescopic image. The field of view spans nearly 2 degrees, or about 4 times the width of the Full Moon, toward the expansive southern constellation Centaurus. About 13 million light-years distant, NGC 4945 is almost the size of our own Milky Way Galaxy. But X-ray and infrared observations reveal even more high energy emission and star formation in the core of NGC 4945. The other prominent galaxy in the field, NGC 4976, is an elliptical galaxy. Left of center, NGC 4976 is much farther away, at a distance of about 35 million light-years, and not physically associated with NGC 4945.

[http://apod.nasa.gov/apod/ap090109.html]

NGC 5253, a peculiar irregular galaxy, is located near the border with Hydra and M83, with which it likely had a close gravitational interaction 1-2 billion years ago. This may have sparked the galaxy’s high rate of star formation, which continues today and contributes to its high surface brightness. NGC 5253 includes a large nebula and at least 12 large star clusters. In the eyepiece, it is a small galaxy of magnitude 10 with dimensions of 5 arcminutes by 2 arcminutes and a bright nucleus:

Hubble Spots a Peculiar Compact Blue Dwarf Galaxy

The NASA/ESA Hubble Space Telescope captured an impressive image of the irregular galaxy NGC 5253. NGC 5253 is one of the nearest of the known Blue Compact Dwarf (BCD) galaxies, and is located at a distance of about 12 million light-years from Earth in the southern constellation of Centaurus. The most characteristic signature of these galaxies is that they harbor very active star-formation regions. This is in spite of their low dust content and comparative lack of elements heavier than hydrogen and helium, which are usually the basic ingredients for star formation.

These galaxies contain molecular clouds that are quite similar to the pristine clouds that formed the first stars in the early Universe, which were devoid of dust and heavier elements. Hence, astronomers consider the BCD galaxies to be an ideal test bed for better understanding the primordial star-forming process. NGC 5253 does contain some dust and heavier elements, but significantly less than the Milky Way galaxy. Its central regions are dominated by an intense star forming region that is embedded in an elliptical main body, which appears red in Hubble’s image. The central starburst zone consists of a rich environment of hot, young stars concentrated in star clusters, which glow in blue in the image. Traces of the starburst itself can be seen as a faint and diffuse glow produced by the ionized oxygen gas.

The true nature of BCD galaxies has puzzled astronomers for a long time. Numerical simulations following the current leading cosmological theory of galaxy formation, known as the Lambda Cold Dark Matter model, predict that there should be far more satellite dwarf galaxies orbiting big galaxies like the Milky Way. Astronomers refer to this discrepancy as the Dwarf Galaxy Problem.

This galaxy is considered part of the Centaurus A/Messier 83 group of galaxies, which includes the famous radio galaxy Centaurus A and the spiral galaxy Messier 83. Astronomers have pointed out the possibility that the peculiar nature of NGC 5253 could result from a close encounter with Messier 83, its closer neighbor.

This image was taken with the Hubble’s Advanced Camera for Surveys, combining visible and infrared exposures. The field of view in this image is approximately 3.4 by 3.4 arcminutes.

[http://www.nasa.gov/mission_pages/hubble/science/ngc5253.html]

NGC 4650A is a polar-ring galaxy. It has a central core made of older stars that resembles an elliptical galaxy, and an outer ring of young stars that orbits around the core. The plane of the outer ring is distorted, which suggests that NGC 4650A is the result of a galaxy collision about a billion years ago. This galaxy has also been cited in studies of dark matter, because the stars in the outer ring orbit too quickly for their collective mass. This suggests that the galaxy is surrounded by a dark matter halo, which provides the necessary mass:

Ring Around NGC 4650A

Space Telescope Science Institute astronomers are giving the public chances to decide where to aim the NASA/ESA Hubble Space Telescope. Guided by 8, 000 Internet voters, Hubble has already been used to take a close-up, multi-color picture of the most popular object from a list of candidates, the extraordinary ‘polar-ring’ galaxy NGC 4650A.

Located about 130 million light-years away, NGC 4650A is one of only 100 known polar-ring galaxies. Their unusual disk-ring structure is not yet understood fully. One possibility is that polar rings are the remnants of colossal collisions between two galaxies sometime in the distant past, probably at least 1 billion years ago. What is left of one galaxy has become the rotating inner disk of old red stars in the center.

[http://www.spacetelescope.org/images/opo9916a/]

One of the closest galaxy clusters to Earth is the Centaurus Cluster, located at a distance of 160 million light-years (redshift 0.0114). It has a cooler, denser central region of gas and a hotter, more diffuse outer region. The intra-cluster medium in the Centaurus Cluster has a high concentration of metals (elements heavier than helium) due to a large number of supernovae. This cluster also possesses a plume of gas whose origin is unknown:

NGC 4696: a cosmic question mark

Curling around itself like a question mark, the unusual looking galaxy NGC 4696 itself begs many questions. Why is it such a strange shape? What are the odd, capillary-like filaments that stretch out of it? And what is the role of a large black hole in explaining its decidedly odd appearance?

This picture, taken by Hubble’s Advanced Camera for Surveys, is not just a beautiful snapshot of NGC 4696, the largest galaxy in the Centaurus Cluster (galaxy cluster Abell 3526). It is also an illustration of the rich variety of objects that astronomers can see with the NASA/ESA Hubble Space Telescope.

NGC 4696 is an elliptical galaxy with a difference. Lacking the complex structure and active star formation of their spiral brethren, elliptical galaxies are usually little more than shapeless collections of ageing stars.

Most likely formed by collisions between spiral galaxies, elliptical galaxies experience a brief burst of star formation triggered as the interstellar dust and gas crash into each other, but which quickly leaves the young elliptical galaxies exhausted. With no more gas to form new stars from, the galaxies gradually grow older and fainter.

But NGC 4696 is more interesting than most elliptical galaxies.

The huge dust lane, around 30 000 light-years across, that sweeps across the face of the galaxy is one way in which it looks different from most other elliptical galaxies. Viewed at certain wavelengths, strange thin filaments of ionized hydrogen are visible within it. In this picture, these structures are visible as a subtle marbling effect across the galaxy’s bright center.

Looking at NGC 4696 in the optical and near-infrared wavelengths seen by Hubble gives a beautiful and dramatic view of the galaxy. But in fact, much of its inner turmoil is still hidden from view in this picture. At the heart of the galaxy, a supermassive black hole is blowing out jets of matter at nearly the speed of light. When looked at in X-ray wavelengths, such as those visible from NASA’s Chandra X-ray Observatory, huge voids within the galaxy become visible, telltale signs of these jets’ enormous power.

The picture was created from images taken using the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys. A total of 5440 s of exposure through a blue filter (F435W, shown in blue) were combined with 2320 s through a near-infrared filter (F814W, shown in red).The field of view is 3.2 by 1.5 arcminutes.

[https://www.spacetelescope.org/news/heic1013/]

NGC 5291 is a system of interacting galaxies in the constellation Centaurus. It is surrounded by a collisional ring, containing young and actively star forming tidal dwarf galaxy, where dark matter has been unexpectedly detected:

[https://en.wikipedia.org/wiki/NGC_5291]

Recycling NGC 5291

Following an ancient galaxy-galaxy collision 200 million light-years from Earth, debris from a gas-rich galaxy, NGC 5291, was flung far into intergalactic space. NGC 5291 and the likely interloper, also known as the ‘Seashell’ galaxy, are captured near the center of this spectacular scene. The sharp, ground-based telescopic image looks toward the galaxy cluster Abell 3574 in the southern constellation Centaurus. Stretched along the 100,000 light-year long tidal tails, are clumps resembling dwarf galaxies, but lacking old stars, apparently dominated by young stars and active star forming regions. Found to be unusually rich in elements heavier than hydrogen and helium, the dwarf galaxies were likely born in intergalactic space, recycling the enriched debris from NGC 5291 itself.

[http://apod.nasa.gov/apod/ap151121.html]

NGC 5090 and NGC 5091 are a set of galaxies approximately 150 million light-years away in the constellation Centaurus. They are in the process of colliding and merging with some evidence of tidal disruption of NGC 5091. NGC 5090 is an elliptical galaxy while NGC 5091 is a spiral galaxy. The velocity of the nucleus of NGC 5091 has been measured as 3429 km/s, while NGC 5090 has a velocity of 3185 km/s:

[https://en.wikipedia.org/wiki/NGC_5090_and_NGC_5091]

Galaxy Pair NGC 5090 and NGC 5091

A pair of galaxies NGC 5090- 5091 in Centaurus is shown in this image. They are located at about the same distance as ESO 269-57 and may belong to the same cluster of galaxies. This is an interacting elliptical-spiral system with some evidence of tidal disruption of NGC 5091 (to the left; seen under a steep angle) by NGC 5090 (to the right). The velocity of the nucleus of NGC 5091 has been measured as 3429 km/sec, while NGC 5090 has a velocity of 3185 km/sec. NGC 5090 is associated with a strong, double radio source (PKS 1318-43). This three-color composite (BVR) was obtained with VLT ANTU and FORS1 in the morning of March 29, 1999. A bright star in the Milky Way, just outside the field at the upper left, has produced a pattern of blue stray-light. The field size is 6.8x6.8 arcmin 2. North is up and East is to the left.

[https://www.eso.org/public/usa/images/eso9924d/]

One of the closest active galaxies to Earth is the Centaurus A galaxy, NGC 5128, at a distance of 11 million light-years (redshift 0.00183). It has a supermassive black hole at its core, which expels massive jets of matter that emit radio waves due to synchrotron radiation. Astronomers posit that its dust lanes, not common in elliptical galaxies, are due to a previous merger with another galaxy, probably a spiral galaxy. NGC 5128 appears in the optical spectrum as a fairly large elliptical galaxy with a prominent dust lane. Its overall magnitude is 7.0, and it has been seen under perfect conditions with the naked eye, making it one of the most distant objects visible to the unaided observer. In equatorial and southern latitudes, it is easily found by star hopping from Omega Centauri. In small telescopes, the dust lane is not visible; it begins to appear with about 4 inches of aperture under good conditions. In large amateur instruments, above about 12 inches in aperture, the dust lane's west-northwest to east-southeast direction is easily discerned. Another dim dust lane on the east side of the 12 arcminute by 15 arcminute galaxy is also visible:

Centaurus A: Merging X-ray data (blue) from NASA’s Chandra X-ray Observatory with microwave (orange) and visible images reveals the jets and radio-emitting lobes emanating from Centaurus A’s central black hole.

Centaurus A, shown with a radio image of its particle jets. Left: The giant elliptical galaxy NGC 5128 is the radio source known as Centaurus A. Vast radio-emitting lobes (shown as orange in this optical/radio composite) extend nearly a million light-years from the galaxy. Right: The radio image provides the sharpest-ever view of a supermassive black hole’s jets. This view reveals the inner 4.16 light-years of the jet and counter-jet, a span less than the distance between our sun and the nearest star. The image resolves details as small as 15 light-days across. Undetected between the jets is the galaxy’s 55-million-solar-mass black hole.

Centaurus A is a giant elliptical active galaxy 12 million light-years away. At its heart lies a black hole with a mass of 55 million suns. Now, the TANAMI project has provided the best-ever image of particle jets powered by the black hole, revealing features as small as 15 light-days across. The jets feed vast lobes of radio-emitting gas that reach far beyond the visible galaxy.

An international team, including NASA-funded researchers, using radio telescopes located throughout the Southern Hemisphere has produced the most detailed image of particle jets erupting from a supermassive black hole in a nearby galaxy.

These jets arise as infalling matter approaches the black hole, but we don’t yet know the details of how they form and maintain themselves,” said Cornelia Mueller, the study’s lead author.

The new image shows a region less than 4.2 light-years across- less than the distance between our sun and the nearest star. Radio-emitting features as small as 15 light-days can be seen, making this the highest-resolution view of galactic jets ever made.

Mueller and her team targeted Centaurus A (Cen A), a nearby galaxy with a supermassive black hole weighing 55 million times the sun’s mass. Also known as NGC 5128, Cen A is located about 12 million light-years away in the constellation Centaurus and is one of the first celestial radio sources identified with a galaxy.

Seen in radio waves, Cen A is one of the biggest and brightest objects in the sky, nearly 20 times the apparent size of a full moon. This is because the visible galaxy lies nestled between a pair of giant radio-emitting lobes, each nearly a million light-years long.

These lobes are filled with matter streaming from particle jets near the galaxy's central black hole. Astronomers estimate that matter near the base of these jets races outward at about one-third the speed of light.

Using an intercontinental array of nine radio telescopes, researchers for the TANAMI (Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry) project were able to effectively zoom into the galaxy’s innermost realm.

The enormous energy output of galaxies like Cen A comes from gas falling toward a black hole weighing millions of times the sun’s mass. Through processes not fully understood, some of this in-falling matter is ejected in opposing jets at a substantial fraction of the speed of light. Detailed views of the jet’s structure will help astronomers determine how they form.

The jets strongly interact with surrounding gas, at times possibly changing a galaxy’s rate of star formation. Jets play an important but poorly understood role in the formation and evolution of galaxies.

[http://www.nasa.gov/topics/universe/features/radio-particle-jets.html]

Centaurus Radio Jets Rising

What if you could see the huge radio jets of Centaurus A rising? The Cen A radio jets are not only over a million light years long, they occupy an angular area over 200 times greater than the full Moon in Earth’s sky. The jets are expelled by a violent black hole millions of times the mass of our Sun embedded deep in the center of nearby active galaxy Cen A. Somehow, the black hole creates the fast moving jets as other matter falls in. In this picture, radio telescopes from the Australian Telescope Compact Array (ATCA) near Narrabri, NSW, Australia, were captured in front of a full Moon, with a radio image of Cen A superposed at its real angular size in the background. The above picture includes the most detailed map yet of any galaxy-class radio jets in the universe, taking several years and over 1,000 hours exposure time to complete. Details in the photo may yield clues as to how radio jets interact with stars and intergalactic dust. The light dots in the image depict not stars, but typically other radio bright galaxies in the even more distant universe.

[http://apod.nasa.gov/apod/ap110413.html]

The Local Interstellar Cloud (LIC), also known as the Local Fluff, is the interstellar cloud roughly 30 light-years (9.2 pc) across through which the Solar System is currently moving. It is currently unknown if the Sun is embedded in the Local Interstellar Cloud, or in the region where the Local Interstellar Cloud is interacting with the neighboring G-Cloud:

[https://en.wikipedia.org/wiki/Local_Interstellar_Cloud]

The Local Fluff

The stars are not alone. In the disk of our Milky Way Galaxy about 10 percent of visible matter is in the form of gas, called the interstellar medium (ISM). The ISM is not uniform, and shows patchiness even near our Sun. It can be quite difficult to detect the local ISM because it is so tenuous and emits so little light. This mostly hydrogen gas, however, absorbs some very specific colors that can be detected in the light of the nearest stars. A working map of the local ISM within 20 light-years, based on ongoing observations and recent particle detections from the Earth-orbiting Interstellar Boundary Explorer satellite (IBEX), is shown above. These observations indicate that our Sun is moving through a Local Interstellar Cloud as this cloud flows outwards from the Scorpius-Centaurus Association star forming region. Our Sun may exit the Local Cloud, also called the Local Fluff, during the next 10,000 years. Much remains unknown about the local ISM, including details of its distribution, its origin, and how it affects the Sun and the Earth. Unexpectedly, recent IBEX spacecraft measurements indicate that the direction from which neutral interstellar particles flow through our Solar System is changing.

[http://apod.nasa.gov/apod/ap130924.html]

The Alpha Centaurids are a meteor shower in the constellation Centaurus, peaking in early February each year. The average magnitude is around 2.5, with a peak of about three meteors an hour. They have been observed since 1969, with a single possible recorded observation in 1938. There was a report of a viewing in 1988, but it was not real.

[https://en.wikipedia.org/wiki/Alpha_Centaurids]

[https://en.wikipedia.org/wiki/Centaurus]

[Return to The 88 Modern Constellations]