Cygnus is a northern constellation lying on the plane of the Milky Way, deriving its name from the Latinized Greek word for swan. Cygnus was among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations. A very large constellation, Cygnus is bordered by Cepheus to the north and east, Draco to the north and west, Lyra to the west, Vulpecula to the south, Pegasus to the southeast and Lacerta to the east. In the equatorial coordinate system, the right ascension coordinates of the constellation lie between 19h 07.3m and 22h 02.3m, while the declination coordinates are between 27.73° and 61.36°. Covering 804 square degrees and around 1.9% of the night sky, Cygnus ranks 16th of the 88 constellations in size.
[http://earthsky.org/favorite-star-patterns/the-northern-cross-backbone-of-the-milky-way]
Normally, Cygnus is depicted with Delta and Epsilon Cygni as its wings, Deneb as its tail, and Albireo as the tip of its beak. The swan is one of the most recognizable constellations of the northern summer and autumn, it features a prominent asterism known as the Northern Cross (in contrast to the Southern Cross). Cygnus culminates at midnight on 29 June, and is most visible in the evening from the early summer to mid-autumn in the Northern Hemisphere.
[https://www.thinglink.com/scene/522841762302001152]
[http://www.wallhapp.com/urano/johann-bayer]
There are several asterisms in Cygnus. In the 17th-century German celestial cartographer Johann Bayer’s star atlas the Uranometria, Alpha, Beta and Gamma Cygni form the pole of a cross, while Delta and Epsilon form the cross beam. The nova P Cygni was then considered to be the body of Christ.
In Greek mythology, Cygnus has been identified with several different legendary swans. Zeus disguised himself as a swan to seduce Leda, Spartan king Tyndareus’s wife, who gave birth to the Gemini, Helen of Troy and Clytemnestra; Orpheus was transformed into a swan after his murder, and was said to have been placed in the sky next to his lyre (Lyra); and the King Cygnus was transformed into a swan.
The Greeks also associated this constellation with the tragic story of Phaethon, the son of Helios the sun god, who demanded to ride his father's sun chariot for a day. Phaethon, however, was unable to control the reins, forcing Zeus to destroy the chariot (and Phaethon) with a thunderbolt, causing it to plummet to the earth into the river Eridanus. According to the myth, Phaethon's brother, Cycnus, grieved bitterly and spent many days diving into the river to collect Phaethon's bones to give him a proper burial. The gods were so touched by Cycnus’s devotion to his brother that they turned him into a swan and placed him among the stars.
In Ovid’s Metamorphoses, there are three people named Cygnus, all of whom are transformed into swans. Alongside Cycnus, noted above, he mentions a boy from Tempe who commits suicide when Phyllius refuses to give him a tamed bull that he demands, but is transformed into a swan and flies away. He also mentions a son of Neptune who is an invulnerable warrior in the Trojan War who is eventually defeated by Achilles, but Neptune saves him by transforming him into a swan.
Together with other avian constellations near the summer solstice, Vultur cadens and Aquila, Cygnus may be a significant part of the origin of the myth of the Stymphalian Birds, one of The Twelve Labours of Hercules.
In Polynesia, Cygnus was often recognized as a separate constellation. In Tonga it was called Tuula-lupe, and in the Tuamotus it was called Fanui-tai. Deneb was also often given a name. In New Zealand it was called Mara-tea, in the Society Islands it was called Pirae-tea or Taurua-i-te-haapa-raa-manu, and in the Tuamotus it was called Fanui-raro. Beta Cygni was named in New Zealand; it was likely called Whetu-kaupo. Gamma Cygni was called Fanui-runga in the Tuamotus.
According to traditional Chinese uranography, the modern constellation Cygnus is located within the northern quadrant of the sky, which is symbolized as the The Black Tortoise of the North (Běi Fāng Xuán Wǔ). The name of the western constellation in modern Chinese is (tiān é zuò), meaning ‘the swan constellation.’
[https://en.wikipedia.org/wiki/Cygnus_%28Chinese_astronomy%29]
[http://www.peoplesguidetothecosmos.com/constellations/cygnus.htm]
[https://mdjslcc.wordpress.com/2012/04/04/star-identification/]
There are several bright stars in Cygnus. Alpha Cygni, called Deneb, is the brightest star in Cygnus. The traditional name is derived from ‘dhaneb,’ Arabic for ‘tail,’ from the phrase ‘Dhanab ad-Dajājah,’ or ‘tail of the hen.’
Deneb is a bluish-white star of spectral type A2Ia, with a surface temperature of 8,500 kelvin. It is the prototype of a class of variable stars known as Alpha Cygni variables. Its surface undergoes non-radial fluctuations which cause its brightness to vary by up to 0.15 magnitude with no clear periodicity, and the spectral type to change slightly. Deneb’s mass is estimated at 19 solar masses (M☉). Its stellar wind causes it to lose mass at a rate of 8±3×10-7 M☉ per year, one hundred thousand times the flow rate from the Sun.
Deneb’s exact distance from the Earth is still rather uncertain. The currently accepted distance is around 2,600 light-years. Deneb’s absolute magnitude is currently estimated as −8.4, placing it among the most luminous stars known, with an estimated luminosity nearly 200,000 times that of the Sun. It is the most luminous of the stars with apparent magnitude brighter than 1.5, and the most distant, by a factor of almost 2, of the 30 brightest stars. Based on its temperature and luminosity, and also on direct measurements of its tiny angular diameter, Deneb appears to have a diameter of about over 200 times that of the Sun. If placed at the center of the Solar System, Deneb would extend out to the orbit of the Earth.
Deneb spent much of its early life as a 23 M☉ O-type main-sequence star but it has now exhausted the supply of hydrogen in its core and begun to cool and expand. Stars in the mass range of Deneb eventually expand to become the most luminous red supergiants, and within a few million years their cores will collapse producing a supernova explosion. It is now known that red supergiants up to a certain mass explode as the commonly seen type II-P supernovae, but more massive ones lose their outer layers to become hotter again. Depending on their initial masses and the rate of mass loss, they may explode as yellow hypergiants or luminous blue variables, or they may become Wolf-Rayet stars before exploding in a type Ib or Ic supernova. Identifying whether Deneb is currently evolving towards a red supergiant or is currently evolving bluewards again would place valuable constraints on the classes of stars that explode as red supergiants and those that explode as hotter stars.
Wide-field view of the Summer Triangle and Milky Way. Deneb is at the left of the frame
The Summer Triangle
Deneb lies at one vertex of a widely spaced asterism called the Summer Triangle, the other two members of which are the zero-magnitude stars Vega in the constellation Lyra and Altair in Aquila. This formation is the approximate shape of a right triangle, with Deneb located at one of the acute angles. The Summer Triangle is recognizable in the northern skies for there are few other bright stars in its vicinity.
Deneb is also easily spotted as the tip of the Northern Cross asterism made up of the brightest stars in Cygnus, the others being Beta (Albireo), Gamma, Delta, and Epsilon Cygni. It never dips below the horizon at or above 45° north latitude, just grazing the northern horizon at its lowest point at such locations as Minneapolis, Montréal and Turin.
In the northern hemisphere Deneb is high in the sky during summer evenings. In the southern hemisphere, Deneb is not at all visible south of 45° south parallel, so it just barely rises above the horizon in Tasmania and southern New Zealand during the southern winter (which corresponds to the northern summer).
Due to the Earth’s axial precession, Deneb will become the Pole star at around 9800 AD.
[https://en.wikipedia.org/wiki/Deneb]
This is just a portion of a huge nebulous region near the bright star Sadr in the constellation of Cygnus. Sadr is the bright star near the center of this image. This image contains many objects, each with their own designation. Among the brightest are IC 1318 (The Butterfly Nebula), IC 1311, and NGC 6888 (The Crescent Nebula). This image is a mosaic of 12 frames, covering approximately 6.2° x 5.5° of sky.
[http://starryvistas.net/Gallery/GammaCygniMosaic/GammaCygni.aspx]
Gamma Cygni is traditionally named Sadr, which means ‘breast’ and refers to its position in the constellation. With an apparent visual magnitude of 2.23, this is among the brighter stars visible in the night sky. Parallax measurements give a distance estimate of 1,800 light years (560 parsecs). The stellar classification of this star is F8 Iab, indicating that it has reached the supergiant stage of its stellar evolution. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.
Compared to the Sun this is an enormous star, with 12 times the Sun’s mass and about 150 times the Sun’s radius. It is emitting over 33,000 times as much energy as the Sun, at an effective temperature of 6,100 K in its outer envelope. This temperature is what gives the star the characteristic yellow-white hue of an F-type star. Massive stars such as this consume their nuclear fuel much more rapidly than the Sun, so the estimated age of this star is only about 12 million years old.
The spectrum of this star shows some unusual dynamic features, including variations in radial velocity of up to 2 km/s, occurring on a time scale of 100 days or more. Indeed its spectrum is markedly like that of a Cepheid variable. This star is surrounded by a diffuse nebula called IC1318, or the Gamma Cygni region.
[https://en.wikipedia.org/wiki/Gamma_Cygni]
Gienah
[https://it.wikipedia.org/wiki/Epsilon_Cygni]
Epsilon Cygni, or Gienah (‘wing’ in Arabic), with an apparent visual magnitude of 2.48, is readily visible to the naked eye at night as one of the brighter members of Cygnus. Based upon parallax measurement, Epsilon Cygni is about 73 light-years from Earth. It is sometimes known as Gienah, but that name is more usually applied to Gamma Corvi.
Epsilon Cygni is a giant star with a stellar classification of K0 III. This indicates that the star has left the main sequence and has begun the final stages in its stellar evolution. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. The effective temperature of the star’s photosphere is 4,710 K, giving Epsilon Cygni an orange hue that is a characteristic of K-type stars. This star has nearly 11 times the solar radius and is about 62 times the luminosity of the Sun.
Radial velocity observations of Epsilon Cygni suggest a possible companion with an orbital period of at least 15 years.
[https://en.wikipedia.org/wiki/Epsilon_Cygni]
[http://panther-observatory.com/gallery/deepsky/doubles/Doublestars_imaged.htm]
Delta Cygni is a third-magnitude star in the constellation Cygnus, and belonged to the Arabic asterism ‘al-Fawāris,’ meaning ‘the Riders,’ together with ζ, ε, and γ Cyg, the transverse of the Northern Cross.
Delta Cygni is a triple star; the system lies at a distance of about 170 light years and consists of two stars quite close together and one much farther out. This sort of common configuration lends stability.
The bright naked-eye star is a blue-white giant of spectral class B9, with a temperature of 10,500 K. It is nearing the end of its main-sequence life stage with a luminosity 155 times that of the Sun, a radius of 5.13 solar radii, and a mass approximately 2.93 solar masses. Like many hot stars, it spins rapidly, at least 135 kilometers per second at the equator, about 60 times that of the Sun. Its close companion is a yellow-white class F of the sixth magnitude (6.33) with a luminosity about 6 times that of the sun, and a mass about 1.5 times that of the sun. The much more distant third companion is an orange (class K) twelfth magnitude star, being only 38% as luminous as the sun, and only 70% as massive as the sun. As seen from Earth, the entire triple star system of Delta Cygni shines at a combined apparent magnitude of 2.86.
It is one of eight bright stars in the northern hemisphere that lay claim to the position of ‘North Star’ over the course of Earth’s 26,000-year precession cycle. It will be the ‘North Star’ for at least four centuries around 11,250.
[https://en.wikipedia.org/wiki/Delta_Cygni]
Albireo’s position, lower right corner. The cross-like figure is the Northern Cross. The blue line shows the boundaries of the constellation the Swan.
Albireo is the traditional name for the double star also designated Beta Cygni. The traditional name is a result of misunderstanding and mistranslation. Medieval Arabic-speaking astronomers called Beta Cygni ‘minqār al-dajājah,’ or ‘Menchir al Dedjadjet,’ meaning ‘the hen’s beak.’ Since Cygnus is the swan, and Beta Cygni is located at the head of the swan, it is sometimes called the ‘beak star.’ With Deneb, Gamma Cygni (Sadr), Delta Cygni, and Epsilon Cygni (Gienah), it forms the asterism called the Northern Cross. It is located about 430 light-years away from the Sun.
Despite being designated ‘beta,’ it is fainter than Gamma Cygni, Delta Cygni, and Epsilon Cygni and is the fifth-brightest point of light in the constellation of Cygnus. Appearing to the naked eye to be a single star of magnitude 3, viewing through even a low-magnification telescope resolves it into its two components. The brighter yellow star (actually itself a very close binary system) makes a striking color contrast with its fainter blue companion.
When viewed with the naked eye, it appears to be a single star. However, in a telescope it readily resolves into a double star, consisting of Beta Cygni A (amber, apparent magnitude 3.1), and Beta Cygni B (blue-green, apparent magnitude 5.1). Separated by 35 seconds of arc, the two components provide one of the best contrasting double stars in the sky due to their different colors. It is not known whether the two components are orbiting around each other in a physical binary system, or if they are merely an optical double. If they are a physical binary, their orbital period is probably at least 100,000 years.
The Beta Cygni A star system has two components, now called Beta Cygni Aa and Beta Cygni Ac, and were identified in the Henry Draper Catalogue as HD 183912 and HD 183913 respectively. An orbit for the pair has since been computed using interferometric measurements, but as only approximately a quarter of the orbit has been observed, the orbital parameters must be regarded as preliminary. The period of this orbit is 213 years. The current angular separation between the components is around 0.4 arcseconds, too close to be visually resolved except with instruments of at least 20" in aperture with exceptionally stable atmospheric conditions.
Beta Cygni B is a fast-rotating Be star, with an equatorial rotational velocity of at least 250 kilometers per second. Its surface temperature has been spectroscopically estimated to be about 13,200 K.
[https://en.wikipedia.org/wiki/Albireo]
A P Cygni profile is a combination of features in a star’s spectrum that points to an outflow of material in the form of either an expanding shell of gas or a powerful stellar wind. The P Cygni profile is characterized by strong emission lines with corresponding blueshifted absorption lines. The latter are produced by material moving away from the star and toward us, whereas the emission comes from other parts of the expanding shell.
[http://www.daviddarling.info/encyclopedia/P/P_Cygni_profile.html]
P Cygni (34 Cyg) is a variable star in the constellation Cygnus, located about 5,000 to 6,000 light-years from Earth. It is a hypergiant luminous blue variable (LBV) star of spectral type B1Ia+ that is one of the most luminous stars in the Milky Way.
Despite the vast distance, it is visible to the naked eye in suitable dark sky locations. It has been called a ‘permanent nova’ because of spectral similarities and the obvious outflow of material, and was once treated with novae as an eruptive variable; however its behavior is no longer thought to involve the same processes associated with true novae.
It is widely considered to be the earliest known example of a luminous blue variable. However it is far from a typical example. It has been largely unvarying both in brightness and spectrum since a series of large outbursts in the 17th century, whereas typical LBV behavior is to show slow variation on a period of years to decades with occasional outbursts where the star shows a significant decrease in temperature and increase in visual brightness at roughly constant luminosity. P Cygni on the other hand, shows only relatively minor brightness and spectral variations, but underwent at least two of the giant eruptions shown only by Eta Carinae and possibly a handful of extra-galactic objects.
P Cygni does show evidence for previous large eruptions around 900, 2,100, and possibly 20,000 years ago. In more recent centuries, it has been very slowly increasing in visual magnitude and decreasing in temperature, which has been interpreted as the expected evolutionary trend of a massive star towards a red supergiant stage.
Luminous blue variables like P Cygni are very rare and short lived, and only form in regions of galaxies where intense star formation is happening. LBV stars are so massive and energetic (typically 50 times the mass of the Sun and tens of thousands of times more luminous) that they exhaust their nuclear fuel very quickly. After shining for only a few million years (compared to several billion years for the Sun) they erupt in a supernova. The recent supernova SN 2006gy was likely the end of an LBV star similar to P Cygni but located in a distant galaxy. P Cygni is thought to be in the hydrogen shell burning phase immediately after leaving the main sequence.
It has been proposed P Cygni’s eruptions could be caused by mass transfer to a hypothetical companion star of spectral type B that would have a mass between 3 and 6 times the mass of the Sun and would orbit P Cygni each 7 years in a high eccentricity orbit. Infall of matter into the secondary star would produce the release of gravitational energy, part of which would cause an increase of the luminosity of the system.
[https://en.wikipedia.org/wiki/P_Cygni]
Cygnus as photographed in infrared light on August 6, 2006. Chi Cygni (arrowed) was the brightest star in the constellation at this wavelength, outshining even Deneb (top left). At visible wavelengths Chi was less bright, magnitude 3.8.
[http://www.skyandtelescope.com/observing/celestial-objects-to-watch/chi-cygnis-record-breaking-maximum/]
Chi Cygni is a variable star of the Mira type in the constellation Cygnus, and also an S-type star. Its apparent visual magnitude varies from as bright as 3.3 to as faint as 14.2. It shows one of the largest variations in apparent magnitude of any pulsating variable star. The observed extremes correspond to a variation of more than 10,000-fold in brightness. Both the maximum and minimum magnitude varies considerably from cycle to cycle: maxima may be brighter than magnitude 4.0 or fainter than 6.0, and minima fainter than magnitude 14.0 or brighter than magnitude 11.0. The maximum of 2015 may have been the faintest ever observed, barely reaching magnitude 6.5, while less than 10 years earlier the 2006 maximum was the brightest for over a century at magnitude 3.8.
Also the period from maximum to maximum or minimum to minimum is not consistent, and can vary by up to 40 days either side of the mean. The mean period depends on the period of observations used, but is generally taken to be 408.7 days. There is some evidence that the mean period has increased by about 4 days over the last three centuries. Period variations on shorter timescales appear to be random rather than cyclical, although it is possible that the secular period increase is not linear.
The spectral type is observed to vary during the brightness changes, from S6 to S10. The earliest spectral types are found at maximum brightness. After maximum, the strength of the emission lines starts to increase. Towards minimum, emission becomes very strong and many unusual forbidden and molecular lines appear.
The diameter of χ Cygni can be measured directly using interferometry. Observations show that the diameter varies from around 19 mas to 26 mas. The size changes are almost in phase with the brightness and spectral type. The smallest size is observed at phase 0.94, which is 30 days before the maximum.
χ Cygni is much larger and cooler than the sun, so large that it is thousands of times more luminous despite the low temperature. It pulsates, with both the radius and temperature varying over approximately 409 days. The temperature varies from about 2,400 K to about 2,700 K and the radius varies from about 350 R☉ to 480 R☉. These pulsations cause the luminosity of the star to vary from about 6,000 L☉ to 9,000 L☉, but they cause the visual brightness to vary by over 10 magnitudes. The huge visual magnitude range is created by a shift of electromagnetic radiation from the infrared as the temperature increases, and by formation at cool temperatures of molecules that absorb visual light.
The annual parallax of χ Cygni has been calculated at 5.53 mas in the new reduction of Hipparcos satellite data, which corresponds to a distance of about 550 light years.
[https://en.wikipedia.org/wiki/Chi_Cygni]
31 Cygni is the close pair. The third star is 30 Cygni.
31 Cygni, also known as ο1 Cygni, Omicron1 Cygni, or V695 Cygni, is another star in the constellation Cygnus. It is an Algol-type eclipsing binary and ranges between magnitudes 3.73 and 3.89 over a period of ten years. The component stars are an orange supergiant of spectrial type K4Iab and a blue-white star likely to be evolving off the main sequence with a spectral type of B4IV-V.
ο2 Cygni is about a degree away to the north, also a detached eclipsing binary system containing a cool giant and a small hot star. 30 Cygni is another naked eye star a tenth of a degree away from the 31 Cygni pair, forming a bright triple.
[https://en.wikipedia.org/wiki/31_Cygni]
The Cygnus OB2 Association
Located some distance from the center of the Cygnus OB2 association, sits Schulte’s star number 12. It’s visual magnitude of -10.6 makes Cyg OB2 #12 the visually brightest star known, in the Milky Way.
[http://www.tim-thompson.com/cyg-ob2-12.html]
H-Alpha light image of Cygnus OB2, the stellar association in which NML Cygni is located
Cygnus OB2 is an OB association, embedded within a wider one of star formation known as Cygnus X, which is one of the most luminous objects in the sky at radio wavelengths, located about 1,740 parsecs away.
Cygnus OB2 is home to some of the most massive and most luminous stars known, including suspected luminous blue variable Cyg OB2 #12. This is an extremely bright blue hypergiant with an absolute bolometric magnitude (all electromagnetic radiation) of −10.9, among the most luminous stars known in the galaxy. This makes the star nearly two million times more luminous than the Sun, although less than half the estimates when the star was first discovered. It is now known to be a binary, with the companion approximately a tenth as bright. A very approximate initial estimate of the orbit gives the total system mass as 120 M☉ and the period as 30 years.
Cygnus OB2 also includes one of the largest known stars, NML Cygni, or V1489 Cygni, a red hypergiant with a radius about 1,183 times the Sun’s, equal to 5.5 astronomical units. If placed at the center of the Solar System, its surface would extend to about the orbit of Jupiter. It contains a volume approximately 1.6 billion times that of the Sun. Its distance from Earth is estimated to be around 1.6 kpc, about 5,300 light-years.
[https://en.wikipedia.org/wiki/Cygnus_OB2]
[https://en.wikipedia.org/wiki/Cygnus_OB2-12]
[https://en.wikipedia.org/wiki/NML_Cygni]
Cygnus is one of the constellations that the Kepler satellite surveyed in its search for extrasolar planets, and as a result, there are about a hundred stars in Cygnus with known planets, the most of any constellation.
The orbit of 16 Cygni Bb (black) compared to the planets in the Solar System.
The naked-eye star 16 Cygni, a triple star approximately 70 light-years from Earth composed of two Sun-like stars and a red dwarf, contains a planet orbiting one of the sun-like stars, found due to variations in the star’s radial velocity.
16 Cygni Bb or HD 186427 b makes one revolution every 799 days and was the first eccentric Jupiter, a planet with a mass at least 1.68 times that of Jupiter (MJ), in a triple star system to be discovered. Unlike the planets in the Solar System, the planet’s orbit is highly elliptical, and its distance varies from 0.54 AU at periastron to 2.8 AU at apastron. Because the planet has only been detected indirectly by measurements of its parent star, properties such as its radius, composition and temperature are unknown. The planet’s highly eccentric orbit means the planet would experience extreme seasonal effects. Despite this, simulations suggest that an Earth-like moon would be able to support liquid water at its surface over the course of a year.
[https://en.wikipedia.org/wiki/16_Cygni_Bb]
Gliese 777 Ac
[https://fr.wikipedia.org/wiki/Gliese_777_Ac]
Gliese 777, often abbreviated as Gl 777 or GJ 777, is a yellow subgiant approximately 52 light-years away in the constellation of Cygnus. The system is also a binary star system made up of two stars and possibly a third. As of 2005, two extrasolar planets are known to orbit the primary star.
The primary star of the system (catalogued as Gliese 777A) is a yellow subgiant, a Sun-like star that is ceasing fusing hydrogen in its core. The star is much older than the Sun, about 6.7 billion years old. It is 4% less massive than the Sun. It is also rather metal-rich, having about 70% more ‘metals’ (elements heavier than helium) than the Sun, which is typical for stars with extrasolar planets.
The secondary star (Gliese 777B) is a distant, dim red dwarf star orbiting the primary at a distance of 3,000 astronomical units. One orbit takes at least tens of thousands of years to complete. The star itself may be a binary, the secondary being a very dim red dwarf. Not much information is available on the star system.
In 2002 a discovery of a long-period, wide-orbiting planet (Gliese 777b) was announced by the Geneva extrasolar planet search team. The planet orbited in circular path and the orbital eccentricity was increased in later measurements (e=0.36). The planet has mass about 1.5 times that of Jupiter and about the same size. In 2005 further observation of the star show another amplitude with a period of 17.1 days. This indicates one of the smallest discovered planets at the time. The mass was only 18 times more than Earth or about same as Neptune with very low eccentricity.
[https://en.wikipedia.org/wiki/Gliese_777]
One of the most notable systems is the Kepler-11 system, containing six transiting planets, all within a plane of approximately one degree. With a spectral type of G6V, the star is somewhat cooler than the Sun. The planets are very close to the star; all but the last planet are closer to Kepler-11 than Mercury is to the Sun, and all the planets are more massive than Earth. Gliese 777, another naked-eye multiple star system containing a yellow star and a red dwarf, also contains a planet. The planet is somewhat similar to Jupiter, but with slightly more mass and a more eccentric orbit:
Kepler-11 is a sun-like star around which six planets orbit. At times, two or more planets pass in front of the star at once, as shown in this artist’s conception of a simultaneous transit of three planets observed by NASA’s Kepler spacecraft on Aug. 26, 2010.
Scientists using NASA’s Kepler, a space telescope, recently discovered six planets made of a mix of rock and gases orbiting a single sun-like star, known as Kepler-11, which is located approximately 2,000 light years from Earth.
“The Kepler-11 planetary system is amazing,” said Jack Lissauer, a planetary scientist and a Kepler science team member at NASA’s Ames Research Center. “It’s amazingly compact, it’s amazingly flat, there’s an amazingly large number of big planets orbiting close to their star- we didn’t know such systems could even exist.”
In other words, Kepler-11 has the fullest, most compact planetary system yet discovered beyond our own.
“Few stars are known to have more than one transiting planet, and Kepler-11 is the first known star to have more than three,” said Lissauer. “So we know that systems like this are not common. There’s certainly far fewer than one percent of stars that have systems like Kepler-11. But whether it’s one in a thousand, one in ten thousand or one in a million, that we don’t know, because we only have observed one of them.”
All of the planets orbiting Kepler-11, a yellow dwarf star, are larger than Earth, with the largest ones being comparable in size to Uranus and Neptune. The innermost planet, Kepler-11b, is ten times closer to its star than Earth is to the sun. Moving outwards, the other planets are Kepler-11c, Kepler-11d, Kepler-11e, Kepler-11f, and the outermost planet, Kepler-11g, which is twice as close to its star than Earth is to the sun.
“The five inner planets are all closer to their star than any planet is to our sun and the sixth planet is still fairly close,” said Lissauer.
If placed in our solar system, Kepler-11g would orbit between Mercury and Venus, and the other five planets would orbit between Mercury and our sun. The orbits of the five inner planets in the Kepler-11 planetary system are much closer together than any of the planets in our solar system. The inner five exoplanets have orbital periods between 10 and 47 days around the dwarf star, while Kepler-11g has a period of 118 days.
“By measuring the sizes and masses of the five inner planets, we have determined they are among the smallest confirmed exoplanets, or planets beyond our solar system,” said Lissauer. “These planets are mixtures of rock and gases, possibly including water. The rocky material accounts for most of the planets’ mass, while the gas takes up most of their volume.”
According to Lissauer, Kepler-11 is a remarkable planetary system whose architecture and dynamics provide clues about its formation. The planets Kepler-11d, Kepler-11e and Kepler-11f have a significant amount of light gas, which Lissauer says indicates that at least these three planets formed early in the history of the planetary system, within a few million years.
A planetary system is born when a molecular cloud core collapses to form a star. At this time, disks of gas and dust in which planets form, called protoplanetary disks, surround the star. Protoplanetary disks can be seen around most stars that are less than a million years old, but few stars more than five million years old have them. This leads scientists to theorize that planets which contain significant amounts of gas form relatively quickly in order to obtain gases before the disk disperses.
The Kepler spacecraft will continue to return science data about the new Kepler-11 planetary system for the remainder of its mission. The more transits Kepler sees, the better scientists can estimate the sizes and masses of planets.
“These data will enable us to calculate more precise estimates of the planet sizes and masses, and could allow us to detect more planets orbiting the Kepler-11 star,” said Lissauer. “Perhaps we could find a seventh planet in the system, either because of its transits or from the gravitational tugs it exerts on the six planets that we already see. We’re going to learn a fantastic amount about the diversity of planets out there, around stars within our galaxy.”
[https://www.nasa.gov/mission_pages/kepler/news/new_planetary_system.html]
This artist’s conception illustrates Kepler-22b, a planet known to comfortably circle in the habitable zone of a sun-like star. It is the first planet that NASA’s Kepler mission has confirmed to orbit in a star’s habitable zone - the region around a star where liquid water, a requirement for life on Earth, could persist. The planet is 2.4 times the size of Earth, making it the smallest yet found to orbit in the middle of the habitable zone of a star like our sun.
[https://www.nasa.gov/content/kepler-22b-closer-to-finding-an-earth]
Kepler-22 is a star in the northern constellation of Cygnus that is orbited by a planet found to be unequivocally within the star’s habitable zone. With an apparent visual magnitude of 11.7, this star is too faint to be seen with the naked eye. It can be viewed with a telescope having an aperture of at least 4 in (10 cm). The estimated distance to Kepler-22 is 620 light-years (190 parsecs).
Kepler-22 is slightly smaller and cooler than the Sun, with a lower abundance of elements having more mass than helium. It has a spectral type of G5V, while the luminosity class remains undetermined. This star is radiating 79% of the Sun’s luminosity from its outer atmosphere at an effective temperature of 5,518 K, giving it the yellow-hued glow of a G-type star. A projected rotational velocity of 0.6 km/s suggests it has a low period of rotation.
A diagram of the orbit of Kepler-22b within the Kepler-22 system, as compared to the inner Solar System, and their respective projected habitable zones.
On December 5, 2011, scientists from the Kepler mission announced that a possible Earthlike world (Kepler-22b) had been discovered orbiting in the star’s habitable zone by NASA’s Kepler spacecraft. This was significant in that it was the first relatively Earth-sized extrasolar planet (about twice as big) confirmed to be orbiting within a star’s habitable zone.
Kepler-22b’s radius is roughly 2.4 times the radius of Earth. Its mass and surface composition remain unknown, with only some very rough estimates established, though the mass is below 52.8 Earth masses to 95% confidence.
The average distance from Kepler-22b to its host star Kepler-22 is about 15% less than the distance from Earth to the Sun but the luminosity (light output) of Kepler-22 is about 25% less than that of the Sun. This combination of a shorter average distance from the star and a lower stellar luminosity are consistent with a moderate surface temperature at that distance if it is assumed that the surface is not subject to extreme greenhouse heating.
The only parameters of the planet’s orbit that are currently available are its period, which is about 290 days, and its inclination, which is approximately 90°, so that it transits the disk of its star as seen from Earth. No information is available about the shape of the planet’s orbit. If Kepler-22b has a highly elongated orbit it may well only spend a small fraction of its time within the habitable zone, which would cause extreme temperature differences on the planet and might make it inhospitable.
Kepler-22b might be an ‘ocean-like’ world. An Earth-like composition is ruled out by radial velocity measurements of the system. It is thus likely to have a more volatile-rich composition with a liquid or gaseous outer shell; this would make it similar to Kepler-11f, the smallest known gas planet.
“If it is mostly ocean with a small rocky core,” Natalie Batalha, one of the scientists on the project, speculated, “it’s not beyond the realm of possibility that life could exist in such an ocean.” This possibility of life has spurred SETI to perform research on top candidates for extraterrestrial intelligence.
The Hunt for Exo-moons with Kepler (HEK) project has studied the Kepler photometry of this planet for evidence of transit timing and duration variations that may be caused by an orbiting satellite. Such variations were not found, ruling out the existence of satellites of Kepler-22b above 0.54 Earth masses at 95% confidence.
[https://en.wikipedia.org/wiki/Kepler-22b]
The artist’s concept depicts Kepler-186f , the first validated Earth-size planet to orbit a distant star in the habitable zone.
[https://www.nasa.gov/ames/kepler/nasas-kepler-discovers-first-earth-size-planet-in-the-habitable-zone-of-another-star]
Kepler-186 is a main-sequence M1-type dwarf star, located about 150 parsecs (500 light years) away in the constellation of Cygnus. The star is slightly cooler than the sun, with roughly half its metallicity. It is known to have five planets, including the first Earth-sized world discovered in the habitable zone: Kepler-186f. The star hosts four other planets discovered so far, though Kepler-186 b, c, and d are too close, but e is near the habitable zone’s inner edge.
The five planets discovered around Kepler-186 are all expected to have a solid surface. The smallest one, Kepler-186b, is only 8% larger than Earth, while the largest one, Kepler-186d, is almost 40% larger.
The four innermost planets are probably tidally locked, but Kepler-186f is further out, where the star’s tidal effects are much weaker, so there may not have been enough time for its spin to slow down that much. Because of the very slow evolution of red dwarf stars, the age of the Kepler-186 system is poorly constrained, although it is likely to be greater than a few billion years. There is a roughly 50-50 chance it is tidally locked. Since it is closer to its star than Earth is to the Sun, it will probably rotate much more slowly than Earth; its day could be weeks or months long.
Planetary formation simulations have also shown that there could be one additional non-transiting low-mass planet between Kepler-186e and Kepler-186f. If this planet exists, it is likely not much more massive than Earth. If it were, its gravitational influence would likely prevent Kepler-186f from transiting. Conjectures indicate that there could be several remaining planets to be found in the system - two small ones between e and f and another larger one outside of f:
[https://en.wikipedia.org/wiki/Kepler-186]
[http://www.wlcastleman.com/astro/nm093011/cygnus_85/cygnus_85_labeled.htm]
[http://www.starobserver.eu/openclusters/ngc6910.html]
There is an abundance of deep-sky objects, with many open clusters, nebulae of various types and supernova remnants found in Cygnus due to its position on the Milky Way. Some open clusters can be difficult to make out from a rich background of stars:
NGC 7092 - Open Cluster in Cygnus
Open cluster NGC 7092 is the brightest and most populous of the many open clusters one can encounter in Cygnus with a magnitude of 4.6. Dominated by multiple member stars ranging in magnitude from 7 to 8, this cluster lies approximately 825 light-years away and spans about 7 light-years. As revealed by the image above, the presence of various bright blue stars indicates that this cluster is not very advanced in age and is estimated to be approximately 230 million years old. The cluster was first discovered by Le Gentil in 1750 and later first observed by Messier in 1764. However, some believe the cluster was known and observed in antiquity by Aristotle. The cluster lies approximately nine degrees from Deneb (α-Cyg, mag 1.33) and can be visible with the naked eye under dark skies. Messier 29 (NGC 6913) is the other Messier open cluster in Cygnus. Both clusters are best observed using low magnifications during summer and early fall where they are placed directly overhead when looking due east.
[http://www.perseus.gr/Astro-DSO-NGC-7092.htm]
The Gamma Cygni Nebula (IC 1318) includes both bright and dark nebulae in an area of over 4 degrees:
Central Cygnus
Supergiant star Gamma Cygni lies at the center of the Northern Cross, famous asterism in the constellation Cygnus the Swan. Known by the proper name Sadr, the bright star also lies at the center of this gorgeous skyscape, featuring a complex of stars, dust clouds, and glowing nebulae along the plane of our Milky Way galaxy. The field of view spans over 3 degrees (six Full Moons) on the sky and includes emission nebula IC 1318 and open star cluster NGC 6910. Left of Gamma Cyg and shaped like two glowing cosmic wings divided by a long dark dust lane, IC 1318’s popular name is understandably the Butterfly Nebula. Above and left of Gamma Cyg, are the young, still tightly grouped stars of NGC 6910. Some distance estimates for Gamma Cyg place it at around 1,800 light-years while estimates for IC 1318 and NGC 6910 range from 2,000 to 5,000 light-years.
[https://apod.nasa.gov/apod/ap070104.html]
Also of note is the Crescent Nebula (NGC 6888), located between Gamma and Eta Cygni, which was formed by the Wolf–Rayet star HD 192163:
NGC 6888: The Crescent Nebula
NGC 6888, also known as the Crescent Nebula, is a cosmic bubble about 25 light-years across, blown by winds from its central, bright, massive star. This beautiful portrait of the nebula is from the Isaac Newton Telescope at Roque de los Muchachos Observatory in the Canary Islands. It combines a composite color image with narrow band data that isolates light from hydrogen and oxygen atoms in the wind-blown nebula. The oxygen atoms produce the blue-green hue that seems to enshroud the detailed folds and filaments. NGC 6888’s central star is classified as a Wolf-Rayet star (WR 136). The star is shedding its outer envelope in a strong stellar wind, ejecting the equivalent of the Sun’s mass every 10,000 years. The nebula’s complex structures are likely the result of this strong wind interacting with material ejected in an earlier phase. Burning fuel at a prodigious rate and near the end of its stellar life this star should ultimately go out with a bang in a spectacular supernova explosion. Found in the nebula rich constellation Cygnus, NGC 6888 is about 5,000 light-years away.
[http://apod.nasa.gov/apod/ap090915.html]
To the south of Epsilon Cygni is the Veil Nebula (NGC 6960, 6962, 6979, 6992, and 6995), a 5,000-year-old supernova remnant covering approximately 3 degrees of the sky- it is over 50 light-years long. Because of its appearance, it is also called the Cygnus Loop. The Loop is only visible in long-exposure astrophotographs. However, the brightest portion, NGC 6992, is faintly visible in binoculars, and a dimmer portion, NGC 6960, is visible in wide-angle telescopes:
The Veil Nebula
Delicate in appearance, these filaments of shocked, glowing gas, draped in planet Earth’s sky toward the constellation of Cygnus, make up the Veil Nebula. The nebula is a large supernova remnant, an expanding cloud born of the death explosion of a massive star. Light from the original supernova explosion likely reached Earth over 5,000 years ago. Also known as the Cygnus Loop, the Veil Nebula now spans nearly 3 degrees or about 6 times the diameter of the full Moon. That translates to over 70 light-years at its estimated distance of 1,500 light-years. In fact, the Veil is so large its brighter parts are recognized as separate nebulae, including The Witch’s Broom (NGC 6960) at the bottom of this stunning skyview and Pickering’s Triangle (NGC 6979) below and right of center. At the top is the haunting IC 1340.
[http://apod.nasa.gov/apod/ap100916.html]
NGC 6826, the Blinking Planetary Nebula, is a planetary nebula with a magnitude of 8.5, 3200 light-years from Earth. It appears to ‘blink’ in the eyepiece of a telescope because its central star is unusually bright (10th magnitude). When an observer focuses on the star, the nebula appears to fade out:
[https://en.wikipedia.org/wiki/NGC_6826]
NGC 6826: The Blinking Eye
The colorful planetary nebula phase of a sun-like star’s life is brief. Almost in the ‘blink of an eye’- cosmically speaking- the star’s outer layers are cast off, forming an expanding emission nebula. This nebula lasts perhaps 10 thousand years compared to a 10 billion year stellar life span. Spectacular planetary nebulae are familiar objects to both professional and amateur astronomers, but they still contain a few surprises. For instance, the lovely nebula NGC 6826, also known as the Blinking Eye Nebula, has mysterious red FLIERS seen on either side of the Hubble Space Telescope image above. Are they also expanding outward from the central star? If so, their ‘bow shocks’ point in the wrong direction!
[https://apod.nasa.gov/apod/ap971219.html]
NGC 7000 is one of the well-known nebulae in Cygnus
The North America Nebula (NGC 7000 or Caldwell 20) is an emission nebula in the constellation Cygnus, close to Deneb (the tail of the swan and its brightest star). The remarkable shape of the nebula resembles that of the continent of North America, complete with a prominent Gulf of Mexico.
The North America Nebula is large, covering an area of more than four times the size of the full moon; but its surface brightness is low, so normally it cannot be seen with the unaided eye. Binoculars and telescopes with large fields of view (approximately 3°) will show it as a foggy patch of light under sufficiently dark skies. However, using a UHC filter, which filters out some unwanted wavelengths of light, it can be seen without magnification under dark skies. Its prominent shape and especially its reddish color (from the hydrogen Hα emission line) show up only in photographs of the area.
The North America Nebula and the nearby Pelican Nebula, (IC 5070) are in fact parts of the same interstellar cloud of ionized hydrogen (H II region). Between the Earth and the nebula complex lies a band of interstellar dust that absorbs the light of stars and nebulae behind it, and thereby determines the shape as we see it. The distance of the nebula complex is not precisely known, nor is the star responsible for ionizing the hydrogen so that it emits light. If the star inducing the ionization is Deneb, as some sources say, the nebula complex would be about 1800 light years distance, and its absolute size (6° apparent diameter on the sky) would be 100 light years.
[https://en.wikipedia.org/wiki/North_America_Nebula]
[http://www.skyandtelescope.com/observing/a-trip-down-the-great-rift/]
The Northern Coalsack Nebula, also called the Cygnus Rift, is a dark nebula located in the Cygnus Milky Way.
In astronomy, the Great Rift (sometimes called the Dark Side, Dark Rift, or, less commonly, Dark River) is a series of overlapping, non-luminous, molecular dust clouds that are located between the Solar System and the Sagittarius Arm of the Milky Way Galaxy at a distance of about 100 parsecs or about 300 light years from Earth. The clouds are estimated to contain about 1 million solar masses of plasma and dust.
To the naked eye, the Great Rift appears as a dark lane that divides the bright band of the Milky Way lengthwise, through about one-third of its extent, and is flanked by lanes of numerous stars. Starting at the constellation of Cygnus, where it is known as the Cygnus Rift or Northern Coalsack, the Great Rift stretches to Aquila; to Ophiuchus, where it broadens out; to Sagittarius, where it obscures the Galactic Center; and finally to Centaurus. One of the most important regions it obscures is the Cygnus OB2 association, a large cluster of young stars and one of the largest regions of star formation near Earth. A similar dark band can be seen in edge-on distant galaxies, such as NGC 891 in Andromeda.
[https://en.wikipedia.org/wiki/Great_Rift_(astronomy)]
Cygnus X is the largest star-forming region in the Solar neighborhood and includes not only some of the brightest and most massive stars known (such as Cygnus OB2-12), but also Cygnus OB2, a massive stellar association classified by some authors as a young globular cluster:
Cygnus-X: The Inner Workings of a Nearby Star Factory
How do stars form? To help study this complex issue, astronomers took a deep infrared image of Cygnus X, the largest known star forming region in the entire Milky Way Galaxy. The above recently-released image was taken in 2009 by the orbiting Spitzer Space Telescope and digitally translated into colors humans can see, with the hottest regions colored the most blue. Visible are large bubbles of hot gas inflated by the winds of massive stars soon after they form. Current models posit that these expanding bubbles sweep up gas and sometimes even collide, frequently creating regions dense enough to gravitationally collapse into yet more stars. The star factory Cygnus-X spans over 600 light years, contains over a million times the mass of our Sun, and shines prominently on wide angle infrared panoramas of the night sky. Cygnus X lies 4,500 light years away towards the constellation of the Swan (Cygnus). In a few million years, calm will likely be restored and a large open cluster of stars will remain- which itself will disperse over the next 100 million years.
[http://apod.nasa.gov/apod/ap120118.html]
Cygnus contains several noteworthy X-ray sources. Located near Eta Cygni is the X-ray source Cygnus X-1, which is now thought to be caused by a black hole accreting matter in a binary star system. This was the first X-ray source widely believed to be a black hole:
Cygnus X-1: NASA’s Chandra Adds to Black Hole Birth Announcement
Cygnus X-1 is a black hole about 15 times the mass of the Sun in orbit with a massive blue companion star. Astronomers used several telescopes including Chandra to study Cygnus X-1. The combined data have revealed the spin, mass, and distance of this black hole more precisely than ever before. Stephen Hawking lost a bet- originally placed in 1974- that Cygnus X-1 did not contain a black hole.
On the left, an optical image from the Digitized Sky Survey shows Cygnus X-1, outlined in a red box. Cygnus X-1 is located near large active regions of star formation in the Milky Way, as seen in this image that spans some 700 light years across. An artist’s illustration on the right depicts what astronomers think is happening within the Cygnus X-1 system. Cygnus X-1 is a so-called stellar-mass black hole, a class of black holes that comes from the collapse of a massive star. The black hole pulls material from a massive, blue companion star toward it. This material forms a disk (shown in red and orange) that rotates around the black hole before falling into it or being redirected away from the black hole in the form of powerful jets.
A trio of papers with data from radio, optical and X-ray telescopes, including NASA’s Chandra X-ray Observatory, has revealed new details about the birth of this famous black hole that took place millions of years ago. Using X-ray data from Chandra, the Rossi X-ray Timing Explorer, and the Advanced Satellite for Cosmology and Astrophysics, scientists were able to determine the spin of Cygnus X-1 with unprecedented accuracy, showing that the black hole is spinning at very close to its maximum rate. Its event horizon- the point of no return for material falling towards a black hole- is spinning around more than 800 times a second.
Using optical observations of the companion star and its motion around its unseen companion, the team also made the most precise determination ever for the mass of Cygnus X-1, of 14.8 times the mass of the Sun. It was likely to have been almost this massive at birth, because of lack of time for it to grow appreciably.
The researchers also announced that they have made the most accurate distance estimate yet of Cygnus X-1 using the National Radio Observatory’s Very Long Baseline Array (VLBA). The new distance is about 6,070 light years from Earth. This accurate distance was a crucial ingredient for making the precise mass and spin determinations.
[http://chandra.harvard.edu/photo/2011/cygx1/index.html]
Cygnus X-3 is a microquasar containing a Wolf- Rayet star in orbit around a very compact object, with a period of only 4.8 hours. The system is one of the most intrinsically luminous X-ray sources observed. Interestingly, the system undergoes periodic outbursts of unknown nature, and during one such outburst, the system was found to be emitting muons, likely caused by neutrinos. While the compact object is thought to be a neutron star or possibly a black hole, it is possible that the object is instead a more exotic stellar remnant, possibly the first discovered quark star, hypothesized due to its production of cosmic rays that cannot be explained if the object is a normal neutron star. The system also emits cosmic rays and gamma rays, and has helped shed insight on to the formation of such rays:
Cyg X-3’s Little Friend: A Stellar Circle of Life
Cygnus X-3 is an X-ray binary where a compact source is pulling material away from a massive companion star. Chandra’s high-resolution X-ray vision revealed a cloud of gas and dust that is a separated by a very small distance from Cygnus X-3. This gas cloud, dubbed the ‘Little Friend,’ is a Bok globule, the first ever detected in X-rays and the most distant one ever discovered. Astronomers detected jets produced by the "Little Friend", showing that a star is forming inside it.
A snapshot of the life cycle of stars has been captured where a stellar nursery is reflecting X-rays from a source powered by an object at the endpoint of its evolution. This discovery, described in our latest press release, provides a new way to study how stars form.
This composite image shows X-rays from NASA’s Chandra X-ray Observatory (white) and radio data from the Smithsonian’s Submillimeter Array (red and blue). The X-ray data reveal a bright X-ray source to the right known as Cygnus X-3, a system containing either a black hole or neutron star (a.k.a. a compact source) left behind after the death of a massive star. Within that bright source, the compact object is pulling material away from a massive companion star. Astronomers call such systems ‘X-ray binaries.’
In 2003, astronomers presented results using Chandra’s high-resolution vision in X-rays to identify a mysterious source of X-ray emission located very close to Cygnus X-3 on the sky (smaller white object to the upper left). The separation of these two sources is equivalent to the width of a penny about 800 feet away. A decade later, astronomers reported the new source is a cloud of gas and dust. In astronomical terms, this cloud is rather small - about 0.7 light years in diameter.
Astronomers realized that this nearby cloud was acting as a mirror, reflecting some of the X-rays generated by Cygnus X-3 towards Earth. They nicknamed this object the ‘Little Friend’ due to its close proximity to Cygnus X-3 on the sky and because it also demonstrated the same 4.8-hour variability in X-rays seen in the X-ray binary.
To determine the nature of the Little Friend, more information was needed. The researchers used the Submillimeter Array (SMA), a series of eight radio dishes atop Mauna Kea in Hawaii, to discover the presence of molecules of carbon monoxide. This is an important clue that helped confirm previous suggestions that the Little Friend is a Bok globule, small, dense, very cold clouds where stars can form. The SMA data also reveal the presence of a jet or outflow within the Little Friend, an indication that a star has started to form inside. The blue portion shows a jet moving towards us and the red portion shows a jet moving away from us.
Distance Estimate: About 20,000 light years
[http://chandra.harvard.edu/photo/2016/cygx3/index.html]
Cygnus A (3C 405) is a radio galaxy in Cygnus, and one of the strongest radio sources in the sky. Like all radio galaxies, it contains an active galactic nucleus. Images of the galaxy in the radio portion of the electromagnetic spectrum show two jets protruding in opposite directions from the galaxy’s center. These jets extend many times the width of the portion of the host galaxy which emits radiation at visible wavelengths. At the ends of the jets are two lobes with ‘hot spots’ of more intense radiation at their edges. These hot spots are formed when material from the jets collides with the surrounding intergalactic medium:
[https://en.wikipedia.org/wiki/Cygnus_A]
Light from Cygnus A
Celebrating astronomy in this International Year of Light, the detailed image reveals spectacular active galaxy Cygnus A in light across the electromagnetic spectrum. Incorporating X-ray data (blue) from the orbiting Chandra Observatory, Cygnus A is seen to be a prodigious source of high energy x-rays. But it is actually more famous at the low energy end of the electromagnetic spectrum. One of the brightest celestial sources visible to radio telescopes, at 600 million light-years distant Cygnus A is the closest powerful radio galaxy. Radio emission ( red) extends to either side along the same axis for nearly 300,000 light-years powered by jets of relativistic particles emanating from the galaxy's central supermassive black hole. Hot spots likely mark the ends of the jets impacting surrounding cool, dense material. Confined to yellow hues, optical wavelength data of the galaxy from Hubble and the surrounding field in the Digital Sky Survey complete a remarkable multiwavelength view.
[https://apod.nasa.gov/apod/ap150124.html]
Cygnus is also the apparent source of the WIMP (weakly interacting massive particles)-wind due to the orientation of the solar system’s rotation through the galactic halo.
[https://en.wikipedia.org/wiki/Cygnus_%28constellation%29]
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