Hydra

[http://dreamview.net/DV/NEW/photos.asp?id=102542&cat=NightSky]

Hydra is the largest of the 88 modern constellations, measuring 1303 square degrees. Also one of the longest at over 100 degrees, its southern end abuts Libra and Centaurus and its northern end borders Cancer. It has a long history, having been included among the 48 constellations listed by the 2nd century astronomer Ptolemy. It is commonly represented as a water snake.

Hydra - Celestial Atlas by Alexander Jamieson, 1822

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

Hydra constellation is usually associated with the second of Heracles’ labors in Greek mythology. Hydra was a giant multi-headed creature fathered by the monster Typhon and Echidna, who was half-woman, half-serpent. The dragon Ladon, that guarded the garden of the Hesperides, was Hydra’s brother. The dragon, also killed by Heracles, is represented by the constellation Draco, while the hero is commemorated by the constellation Hercules.

In mythology, Hydra had nine heads and one of them was immortal. The celestial Hydra is depicted with only one head, presumably the immortal one. The monster lived near the town of Lerna, where it ravaged the land and killed cattle. Heracles, faced with a difficult task, first shot flaming arrows into the Hydra’s lair and smoked it out. Then he fought with it, smashing the creature’s heads one by one with his club. Every time he smashed one, two new heads would grow in its place. While the two fought, Heracles was distracted by a crab, which crawled out of the swamp and attacked his foot. Heracles killed the crab and Hera, a sworn enemy of his, placed it among the stars as the constellation Cancer.

Heracles was able to defeat the Hydra when his charioteer Iolaus helped him by burning the stumps of each head that Heracles struck off, and eventually Heracles cut off the immortal head and buried it under a rock. He dipped his arrows in Hydra’s poisonous blood, which would eventually lead to his own death.

In a different myth, the constellation Hydra is associated with the water snake on which Apollo’s crow blamed its tardiness. The god had sent the bird, represented by the constellation Corvus, to fetch him some water in a cup. The cup is associated with the constellation Crater. The crow was distracted by a fig tree and stopped to feast. When it finally returned to Apollo, it said the water snake was to blame, but the god saw through the bird’s lie and punished it by placing it into the sky. Apollo also turned the water snake and the cup into constellations. In the sky, the water snake (Hydra) eternally prevents the crow (Corvus) from drinking out of the cup (Crater).

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

The Greek constellation of Hydra is an adaptation of a Babylonian constellation: the MUL.APIN includes a ‘serpent’ constellation (MUL.DINGIR.MUŠ) that loosely corresponds to Hydra. It is one of two Babylonian ‘serpent’ constellations (the other being the origin of the Greek Serpens), a mythological hybrid of serpent, lion and bird.

In Hindu Mythology the star that equivalents Hydra is Ashlesha.

In Chinese astronomy, the stars that correspond to Hydra are located within the Vermilion Bird and the Azure Dragon.

In Japanese culture, the stars are known as Nuriko.

The winding constellation Hydra in the southern April sky, below Cancer, Leo, Virgo, and Libra

[http://oneminuteastronomer.com/1408/constellation-hydra/]

Hydra, the largest of the 88 constellations, consists of mostly faint stars. By good fortune, four bright luminaries- Spica (α Virginis), Saturn, Regulus (α Leonis) and Mars- parallel the constellation and serve as guides to help you trace its full length. This map shows the sky as you face south around 9:45 p.m. (11 May 2010).

[http://astrobob.areavoices.com/2010/05/11/more-cowbell/]

Alphard

[https://sites.google.com/site/alphardthebrighteststar/]

Despite its size, Hydra contains only one reasonably bright star, Alphard, designated Alpha Hydrae. The traditional name Alphard is from the Arabic ‘al-fard,’ ‘the solitary one,’ there being no other bright stars near it. It was also known as the ‘backbone of the Serpent’ to the Arabs.

Alphard has three times the mass of the Sun. Its estimated age is 420 million years and it has evolved away from the main sequence to become a giant star with a spectral classification of K3 and luminosity class between II and III. The angular diameter has been measured using long-baseline interferometry, yielding a value of about 9 milliarcseconds, only beaten in it by Betelgeuse and R Doradus. It has expanded to 50 times the radius of the Sun.

Alphard’s spectrum shows a mild excess of barium, an element that is normally produced by the s-process of nucleosynthesis. Typically a barium star belongs to a binary system and the anomalies in abundances are explained by mass transfer from a companion white dwarf star.

Precise radial velocity measurements have shown variations in the stellar radial velocities and spectral line profiles. The oscillations are multi-periodic with periods from several hours up to several days. The short-term oscillations were assumed to be a result of stellar pulsations, similar to the solar ones. A correlation between the variations in the asymmetry of the spectral line profile and the radial velocity has also been found. The multi-periodic oscillations make HD 81797 (Alphard) an object of interest for asteroseismologic investigations.

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

Gamma Hydrae has an apparent visual magnitude of 3.0, placing it second in brightness among the members of this generally faint constellation. This star is at a distance of around 133.8 light-years (41.0 parsecs) from Earth.

The spectrum matches a stellar classification of G8 III, with the luminosity class of III indicating it has evolved into a giant star after exhausting the supply of hydrogen at its core. The interferometry-measured uniform disk angular diameter of this star is 2.96 ± 0.15 mas, which, at its estimated distance, equates to a physical radius of roughly 13 times the radius of the Sun. It has nearly three times the mass of the Sun and is radiating 115 times the Sun’s luminosity from its outer atmosphere at an effective temperature of 5,019 K. This heat gives it the yellow glow of a K-type star. Despite having reached an advanced stage in its evolution, it is considerably younger than the Sun with an age of around 372 million years. This is because higher mass stars consume their nuclear fuel at a more rapid rate.

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

The bow shock around R Hya

R Hydrae, also known as R Hya, is a Mira-type variable star in the constellation Hydra. The magnitude of R Hydrae varies over a period of 389 days, between 3.5 and 10.9. The period of R Hydrae changes slowly. At maximum brightness the star can be seen with the naked eye, while at minimum a telescope of at least 5 cm is needed. R Hydrae is approximately 400 light years from Earth. Its spectral class is M7IIIe.

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

Delta Hydrae is a double star in the constellation of Hydra. It is visible to the naked eye with an apparent visual magnitude of 4.146. It is located about 160 light years from the Sun.

The brighter component is an A-type main sequence star with a stellar classification of A1 Vnn. It is spinning rapidly with a projected rotational velocity of 285 km/s. This is giving the star an oblate shape with an equatorial bulge that is 20% larger than the polar radius. It has an estimated 2.88 times the mass of the Sun and 2.7 times the Sun’s radius. The star is about 244 million years old and it radiates 42.7 times the solar luminosity from its outer atmosphere at an effective temperature of 11,055 K.

The companion has a visual magnitude of 11.15. X-ray emissions have been detected from this location in space, which may be coming from a companion star.

In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Lisan al Shudja, which was translated into Latin as Lingua Hydri, meaning the snake’s tongue.

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

V Hydrae is a semiregular variable binary carbon star of type SRa, sometimes considered to be a Mira variable. It pulsates with a period of 530 days and a brightness range of 1-2 magnitudes, but also shows deep fades at intervals of about 6,160 days when it may drop below magnitude 12:

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

This four-panel graphic illustrates how the binary-star system V Hydrae is launching balls of plasma into space.

Great balls of fire! NASA’s Hubble Space Telescope has detected superhot blobs of gas, each twice as massive as the planet Mars, being ejected near a dying star. The plasma balls are zooming so fast through space it would take only 30 minutes for them to travel from Earth to the moon. This stellar ‘cannon fire’ has continued once every 8.5 years for at least the past 400 years, astronomers estimate.

The fireballs present a puzzle to astronomers, because the ejected material could not have been shot out by the host star, called V Hydrae. The star is a bloated red giant, residing 1,200 light-years away, which has probably shed at least half of its mass into space during its death throes. Red giants are dying stars in the late stages of life that are exhausting the nuclear fuel that makes them shine. They have expanded in size and are shedding their outer layers into space.

The current best explanation suggests the plasma balls were launched by an unseen companion star. According to this theory, the companion would have to be in an elliptical orbit that carries it close to the red giant's puffed-up atmosphere every 8.5 years. As the companion enters the bloated star's outer atmosphere, it gobbles up material. This material then settles into a disk around the companion, and serves as the launching pad for blobs of plasma, which travel at roughly a half-million miles per hour.

This star system could be the archetype to explain a dazzling variety of glowing shapes uncovered by Hubble that are seen around dying stars, called planetary nebulae, researchers say. A planetary nebula is an expanding shell of glowing gas expelled by a star late in its life.

“We knew this object had a high-speed outflow from previous data, but this is the first time we are seeing this process in action,” said Raghvendra Sahai, lead author of the study. “We suggest that these gaseous blobs produced during this late phase of a star's life help make the structures seen in planetary nebulae.”

Hubble observations over the past two decades have revealed an enormous complexity and diversity of structure in planetary nebulae. The telescope’s high resolution captured knots of material in the glowing gas clouds surrounding the dying stars. Astronomers speculated that these knots were actually jets ejected by disks of material around companion stars that were not visible in the Hubble images. Most stars in our Milky Way galaxy are members of binary systems. But the details of how these jets were produced remained a mystery.

“We want to identify the process that causes these amazing transformations from a puffed-up red giant to a beautiful, glowing planetary nebula,” Sahai said. "These dramatic changes occur over roughly 200 to 1,000 years, which is the blink of an eye in cosmic time.”

Sahai’s team used Hubble’s Space Telescope Imaging Spectrograph (STIS) to conduct observations of V Hydrae and its surrounding region over an 11-year period, first from 2002 to 2004, and then from 2011 to 2013. Spectroscopy decodes light from an object, revealing information on its velocity, temperature, location and motion.

The data showed a string of monstrous, superhot blobs, each with a temperature of more than 17,000 degrees Fahrenheit (9,400 degrees Celsius)- almost twice as hot as the surface of the sun. The researchers compiled a detailed map of the blobs’ locations, allowing them to trace the first behemoth clumps back to 1986. “The observations show the blobs moving over time,” Sahai said. “The STIS data show blobs that have just been ejected, blobs that have moved a little farther away, and blobs that are even farther away.” STIS detected the giant structures as far away as 37 billion miles (60 billion kilometers) away from V Hydrae, more than eight times farther away than the Kuiper Belt of icy debris at the edge of our solar system is from the sun.

The blobs expand and cool as they move farther away, and are then not detectable in visible light. But observations taken at longer, sub-millimeter wavelengths in 2004, by the Submillimeter Array in Hawaii, revealed fuzzy, knotty structures that may be blobs launched 400 years ago, the researchers said.

Based on the observations, Sahai and his colleagues Mark Morris of the University of California, Los Angeles, and Samantha Scibelli of the State University of New York at Stony Brook developed a model of a companion star with an accretion disk to explain the ejection process.

“This model provides the most plausible explanation because we know that the engines that produce jets are accretion disks,” Sahai explained. “Red giants don’t have accretion disks, but many most likely have companion stars, which presumably have lower masses because they are evolving more slowly. The model we propose can help explain the presence of bipolar planetary nebulae, the presence of knotty jet-like structures in many of these objects, and even multipolar planetary nebulae. We think this model has very wide applicability.”

A surprise from the STIS observation was that the disk does not fire the monster clumps in exactly the same direction every 8.5 years. The direction flip-flops slightly, from side-to-side to back-and-forth, due to a possible wobble in the accretion disk. “This discovery was quite surprising, but it is very pleasing as well because it helped explain some other mysterious things that had been observed about this star by others,” Sahai said.

Astronomers have noted that V Hydrae is obscured every 17 years, as if something is blocking its light. Sahai and his colleagues suggest that due to the back-and-forth wobble of the jet direction, the blobs alternate between passing behind and in front of V Hydrae. When a blob passes in front of V Hydrae, it shields the red giant from view.

“This accretion disk engine is very stable because it has been able to launch these structures for hundreds of years without falling apart,” Sahai said. “In many of these systems, the gravitational attraction can cause the companion to actually spiral into the core of the red giant star. Eventually, though, the orbit of V Hydrae’s companion will continue to decay because it is losing energy in this frictional interaction. However, we do not know the ultimate fate of this companion.”

The team hopes to use Hubble to conduct further observations of the V Hydrae system, including the most recent blob ejected in 2011. The astronomers also plan to use the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to study blobs launched over the past few hundred years that are now too cool to be detected with Hubble.

[https://www.jpl.nasa.gov/news/news.php?feature=6639]

TW Hydrae is a T Tauri star approximately 176 light-years away, being the closest such star to the Solar System. TW Hydrae is about 80% of the mass of the Sun, but is only about 5-10 million years old. The star appears to be accreting from a face-on protoplanetary disk of dust and gas, which has been resolved in images from the ALMA observatory. TW Hydrae is accompanied by about twenty other low-mass stars with similar ages and spatial motions, comprising the ‘TW Hydrae association’ or TWA, one of the closest regions of recent ‘fossil’ star-formation to the Sun:

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

ALMA image of the planet-forming disk around the young, Sun-like star TW Hydrae. The inset image (upper right) zooms in on the gap nearest to the star, which is at the same distance as the Earth is from the Sun, suggesting an infant version of our home planet could be emerging from the dust and gas. The additional concentric light and dark features represent other planet-forming regions farther out in the disk.

The disks of dust and gas that surround young stars are the formation sites of planets. New images from the Atacama Large Millimeter/submillimeter Array (ALMA) reveal never-before-seen details in the planet-forming disk around a nearby Sun-like star, including a tantalizing gap at the same distance from the star as the Earth is from the Sun.

This structure may mean that an infant version of our home planet, or possibly a more massive ‘super-Earth,’ is beginning to form there.

The star, TW Hydrae, is a popular target of study for astronomers because of its proximity to Earth (approximately 175 light-years away) and its status as a veritable newborn (about 10 million years old). It also has a face-on orientation as seen from Earth. This affords astronomers a rare, undistorted view of the complete disk.

“Previous studies with optical and radio telescopes confirm that this star hosts a prominent disk with features that strongly suggest planets are beginning to coalesce,” said Sean Andrews, lead author of the study. “The new ALMA images show the disk in unprecedented detail, revealing a series of concentric dusty bright rings and dark gaps, including intriguing features that suggest a planet with an Earth-like orbit is forming there.”

Other pronounced gap features are located 3 billion and 6 billion kilometers from the central star, similar to the distances from the Sun to Uranus and Pluto in our own Solar System. They too are likely the result of particles that came together to form planets, which then swept their orbits clear of dust and gas and shepherded the remaining material into well-defined bands.

For the new TW Hydrae observations, astronomers imaged the faint radio emission from millimeter-size dust grains in the disk, revealing details on the order of one astronomical unit (about 150 million kilometers, or the distance between the Earth and the Sun). These detailed observations were made possible with ALMA’s high-resolution, long-baseline configuration. When ALMA’s dishes are at their maximum separation, up to nearly 15 kilometers apart, the telescope is able to resolve finer details. “This is the highest spatial resolution image ever of a protoplanetary disk from ALMA, and that won’t be easily beaten going forward,” said Andrews.

“TW Hydrae is quite special. It is the nearest known protoplanetary disk to Earth and it may closely resemble our Solar System when it was only 10 million years old,” said co-author David Wilner, co-author.

Earlier ALMA observations of another system, HL Tau, show that even younger protoplanetary disks– a mere one million years old– can display similar signatures of planet formation. By studying the older TW Hydrae disk, astronomers hope to better understand the evolution of our own planet and the prospects for similar systems throughout the Galaxy.

The astronomers’ next phase of research is to investigate how common these kinds of features are in disks around other young stars and how they might change with time or environment.

[https://public.nrao.edu/news/2016-alma-twhya/]

One possible non-radial oscillation mode of Xi Hydrae

Xi Hydrae (Xi Hya) is a solitary star in the equatorial constellation of Hydra. This magnitude 3.54 star is situated 130 light-years from Earth and has a radius about 10 times that of the Sun. It is radiating 58 times as much luminosity as the Sun. The star is now approaching the end of its life, and has expanded its outer envelope to become a red giant star.

The star Xi Hya was particularly interesting in the field of asteroseismology when an international group of astronomers discovered that it behaves like a giant sub-ultra-bass musical instrument.

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

Artist’s impression of Gliese 433

[https://de.wikipedia.org/wiki/Gliese_433]

Gliese 433 is a dim red dwarf star in the constellation of Hydra, roughly 29.5 light years away from the Sun. Astronomers have announced the discovery of a very low-mass extrasolar planet in close orbit.

Gliese 433 b is an extrasolar planet which orbits the star. This planet is a super-Earth with at least six times the mass of Earth and takes approximately seven days to orbit the star at a semimajor axis of approximately 0.056 AU. This planet was announced in 2009, and was confirmed in 2014.

[https://en.wikipedia.org/wiki/Gliese_433]

Position of HD 70573 in Hydra constellation

[https://de.wikipedia.org/wiki/HD_70573]

HD 70573 is a 9th magnitude star approximately 149 light-years away in the constellation of Hydra. The star is young, only 101 million years old.

On March 19, 2007, an extrasolar planet was announced, having been discovered by the radial velocity method. This is thus far the youngest host star discovered to have an orbiting planet.

[https://en.wikipedia.org/wiki/HD_70573]

HE1327-2326

[http://www.daviddarling.info/encyclopedia/H/HE1327-2326.html]

HE1327-2326 was the star with the lowest known iron abundance until SMSS J031300.36-670839.3 was discovered. The star is a member of Population II stars, with an iron to hydrogen ratio ([Fe/H]), or metallicity, of −5.6. This number indicates that its iron content is 1/400,000 that of the Earth’s sun. However, it has a carbon abundance of roughly one-tenth solar ([C/H] = −1.0), and it is not known how these two abundances can be produced simultaneously. Discovered by the Hamburg/ESO survey for metal-poor stars, it was probably formed during an age of the universe when the metal content was much lower. It has been speculated that this star is part of the second generation, born out of the gas clouds which were polluted by the primordial Population III stars.

[https://en.wikipedia.org/wiki/HE_1327-2326]

Messier 48

Messier 48 (also known as M 48 or NGC 2548) is an open cluster in the Hydra constellation. It was discovered by Charles Messier in 1771. It is visible to the naked eye under good atmospheric conditions. Its age is estimated to amount 300 million years.

[https://en.wikipedia.org/wiki/Messier_48]

A 2012 view of M68 from the Wide Field Camera of Hubble’s Advanced Camera for Surveys

Messier 68 (also known as M68 or NGC 4590) is a globular cluster in the equatorial constellation Hydra. It was discovered by Charles Messier in 1780. William Herschel described it as “a beautiful cluster of stars, extremely rich, and so compressed that most of the stars are blended together.” His son John noted that it was “all clearly resolved into stars of 12th magnitude, very loose and ragged at the borders.”

M68 is at a distance of about 33,000 light-years away from Earth and is orbiting through the galaxy with a large eccentricity of 0.5. This orbit carries it as far as 100,000 light years from the galactic center. It is one of the most metal-poor globular clusters, which means it has a paucity of elements other than hydrogen and helium. The cluster may be undergoing core-collapse, and it displays signs of being in rotation. The cluster may have been acquired by the Milky Way galaxy through accretion from a satellite galaxy.

All told, as of 2015 a total of 50 variable stars have been identified in this cluster; the first 28 being identified as early as 1919−1920 by American astronomer Harlow Shapley. Most of the variables are of type RR Lyrae, or periodic variables. Six of the variables are of the SX Phoenicis variety, which display short pulsating behavior.

[https://en.wikipedia.org/wiki/Messier_68]

NGC 3242 (Ghost of Jupiter/Jupiters Geist) in Hydra

[http://www.capella-observatory.com/ImageHTMLs/PNs/NGC3242.htm]

NGC 3242 is most frequently called the Ghost of Jupiter, or Jupiter’s Ghost due to its similar size to the planet, but it is also sometimes referred to as the Eye Nebula. The nebula measures around two light years long from end to end, and contains a central white dwarf with an apparent magnitude of eleven. The inner layers of the nebula were formed some 1,500 years ago. The two ends of the nebula are marked by FLIERs, lobes of fasting moving gas often tinted red in false-color pictures. NGC 3242 can easily be observed with amateur telescopes, and appears bluish-green to most observers. Larger telescopes can distinguish the outer halo as well.

[https://en.wikipedia.org/wiki/NGC_3242]

Abell 33 is a planetary nebula located 2700 light years away in the constellation of Hydra. It lies just behind the star HD 83535. The star HD 83535 is also responsible for the ‘diamond ring’ effect seen in the photograph:

[https://en.wikipedia.org/wiki/Abell_33]

The planetary nebula Abell 33 captured using ESO’s Very Large Telescope

Astronomers using ESO’s Very Large Telescope in Chile have captured this eye-catching image of planetary nebula Abell 33. Created when an aging star blew off its outer layers, this beautiful blue bubble is, by chance, aligned with a foreground star, and bears an uncanny resemblance to a diamond engagement ring. This cosmic gem is unusually symmetric, appearing to be almost perfectly circular on the sky.

[https://www.eso.org/public/images/eso1412a/]

M83 (NGC 5236), the Southern Pinwheel Galaxy, is an 8th magnitude face-on spiral galaxy. It is easily observed in skies south of 40°N latitude, found by using 1, 2, 3, and 4 Centauri as guide stars. It has been host to six supernovae, more than any Messier object. Large amateur telescopes- above 12 inches aperture- reveal its spiral arms, bar, and small, bright nucleus. In a medium-sized amateur instrument, around 8 inches in aperture, the spiral arms become visible under good conditions. It is not perfectly symmetrical in the eyepiece, rather, the northwest side is flattened and the nucleus has a southwest-to-northeast bar. A smaller sister to the Milky Way, it is a grand design spiral galaxy 40,000 light-years across:

M83: The Thousand-Ruby Galaxy

Big, bright, and beautiful, spiral galaxy M83 lies a mere twelve million light-years away, near the southeastern tip of the very long constellation Hydra. Prominent spiral arms traced by dark dust lanes and blue star clusters lend this galaxy its popular name, The Southern Pinwheel. But reddish star forming regions that dot the sweeping arms highlighted in this sparkling color composite also suggest another nickname, The Thousand-Ruby Galaxy. About 40,000 light-years across, M83 is a member of a group of galaxies that includes active galaxy Centaurus A. In fact, the core of M83 itself is bright at x-ray energies, showing a high concentration of neutron stars and black holes left from an intense burst of star formation. This sharp composite color image also features spiky foreground Milky Way stars and distant background galaxies. The image data was taken from the Subaru Telescope, the European Southern Observatory's Wide Field Imager camera, and the Hubble Legacy Archive.

[http://apod.nasa.gov/apod/ap151008.html]

SN 1957D, a young supernova remnant was discovered in M83:

SN 1957D in M83: X-Rays Discovered from Young Supernova Remnant

Over fifty years ago, a supernova was discovered in M83, a spiral galaxy about 15 million light years from Earth. Astronomers have used NASA’s Chandra X-ray Observatory to make the first detection of X-rays emitted by the debris from this explosion.

Named SN 1957D because it was the fourth supernova to be discovered in the year of 1957, it is one of only a few located outside of the Milky Way galaxy that is detectable, in both radio and optical wavelengths, decades after its explosion was observed. In 1981, astronomers saw the remnant of the exploded star in radio waves, and then in 1987 they detected the remnant at optical wavelengths, years after the light from the explosion itself became undetectable.

A relatively short observation- about 14 hours long- from NASA’s Chandra X-ray Observatory in 2000 and 2001 did not detect any X-rays from the remnant of SN 1957D. However, a much longer observation obtained in 2010 and 2011, totaling nearly 8 and 1/2 days of Chandra time, did reveal the presence of X-ray emission. The X-ray brightness in 2000 and 2001 was about the same as or lower than in this deep image.

This new Chandra image of M83 is one of the deepest X-ray observations ever made of a spiral galaxy beyond our own. This full-field view of the spiral galaxy shows the low, medium, and high-energy X-rays observed by Chandra in red, green, and blue respectively. The location of SN 1957D, which is found on the inner edge of the spiral arm just above the galaxy's center, is outlined in the box.

The new X-ray data from the remnant of SN 1957D provide important information about the nature of this explosion that astronomers think happened when a massive star ran out of fuel and collapsed. The distribution of X-rays with energy suggests that SN 1957D contains a neutron star, a rapidly spinning, dense star formed when the core of pre-supernova star collapsed. This neutron star, or pulsar, may be producing a cocoon of charged particles moving at close to the speed of light known as a pulsar wind nebula.

If this interpretation is confirmed, the pulsar in SN 1957D is observed at an age of 55 years, one of the youngest pulsars ever seen. The remnant of SN 1979C in the galaxy M100 contains another candidate for the youngest pulsar, but astronomers are still unsure whether there is a black hole or a pulsar at the center of SN 1979C.

Multipanel with Optical, H-alpha & X-ray.

An image from the Hubble Space Telescope shows that the debris of the explosion that created SN 1957D is located at the edge of a star cluster less than 10 million years old. Many of these stars are estimated to have masses about 17 times that of the Sun. This is just the right mass for a star’s evolution to result in a core-collapse supernova as is thought to be the case in SN 1957D.

[http://chandra.harvard.edu/photo/2012/m83sn/index.html]

ESO 510-G13 is a warped spiral galaxy located 150 million light-years from Earth. Though most galactic disks are flat because of their rate of rotation, their conformation can be changed, as is the case with this galaxy. Astronomers speculate that this is due to interactions with other galaxies:

ESO 510-G13, a heavily warped spiral galaxy

ESO 510-G13 is a heavily warped edge-on spiral galaxy about 150 million light-years away in the southern constellation Hydra. The galaxy illustrates that a galaxy’s disk is very fragile and can be easily distorted by gravity caused by interacting galaxies.

The most prominent features in this image are the galaxy’s heavily warped thin disk of stars, gas, and dust, its glowing central bulge, composed mostly of old stars, and its bright clusters of blue stars. The dark clouds of gas and dust in the disk stand out in this picture because they block the light of background stars, and because they are silhouetted from behind by light from the galaxy’s bright, smooth central bulge.

In the outer regions of ESO 510-G13, especially visible on the right-hand side of the image, the bent disk contains not only dark dust but also bright clusters of blue stars. These clusters are evidence that hot, young stars are being formed in the disk.

The strong warping of the disk indicates that ESO 510-G13 has recently undergone a collision with a nearby galaxy and is in the process of swallowing it. The formation of new stars is most likely triggered by this collision.

When galaxies collide, clouds of dust and gas smash together and are compressed in a process that takes millions of years, creating a favorable environment for star birth. Eventually the disturbances will die out, and ESO 510-G13 will become a normal-appearing single galaxy.

Much of ESO 510-G13 appears whitish because it contains stars of many different colors, which combine to create a white appearance in the image. However, near the dark band of dusty gas slicing through the middle of this galaxy, the starlight appears redder because the dusty gas blocks blue light more effectively than red light.

[http://annesastronomynews.com/photo-gallery-ii/galaxies-clusters/eso-510-g13/]

NGC 3314, usually delineated as NGC 3314a and NGC 3314b, is a pair of galaxies that appear superimposed, despite the fact that they are not related or interacting in any way. The foreground galaxy, NGC 3314a, is at a distance of 140 million light-years, and is a face-on spiral galaxy. The background galaxy, NGC 3314b, is an oblique spiral galaxy, and has a nucleus that appears reddened because of NGC 3314a’s dusty disk:

NGC 3314: When Galaxies Overlap

NGC 3314 is actually two large spiral galaxies which just happen to almost exactly line up. The foreground spiral is viewed nearly face-on, its pinwheel shape defined by young bright star clusters. But against the glow of the background galaxy, dark swirling lanes of interstellar dust appear to dominate the face-on spiral’s structure. The dust lanes are surprisingly pervasive, and this remarkable pair of overlapping galaxies is one of a small number of systems in which absorption of light from beyond a galaxy's own stars can be used to directly explore its distribution of dust. NGC 3314 is about 140 million light-years (background galaxy) and 117 million light-years (foreground galaxy) away in the multi-headed constellation Hydra. The background galaxy would span nearly 70,000 light-years at its estimated distance. A synthetic third channel was created to construct this dramatic new composite of the overlapping galaxies from two color image data in the Hubble Legacy Archive.

[http://apod.nasa.gov/apod/ap110715.html]

Abell 3411 is a galaxy cluster located about two billion light years from Earth and weighs about a million billion times the mass of the Sun:

[https://en.wikipedia.org/wiki/Abell_3411]

Abell 3411 and 3412: Astronomers discover powerful cosmic double whammy

Using data from NASA’s Chandra X-ray Observatory and several other telescopes, astronomers have discovered a cosmic one-two punch unlike any ever seen in a pair of colliding galaxy clusters called Abell 3411 and Abell 3412. This result, described in our latest press release, shows that an eruption from a supermassive black hole combined with a galaxy cluster merger can create a stupendous cosmic particle accelerator.

This composite image contains X-rays from Chandra (blue) that reveals diffuse emission from multi-million-degree gas in the two clusters. The comet-shaped appearance of the hot gas provides clear evidence that the two clusters are colliding and merging. The ‘head’ of the comet is hot gas from one cluster plowing through the hot gas of the other cluster, in the direction shown by the arrow in the labeled image.

Radio emission detected by the Giant Metrewave Radio Telescope in India (red) represents colossal shock waves- cosmic versions of sonic booms generated by supersonic aircraft- produced by the collision of the hot gas associated with the galaxy clusters. Optical data from the Subaru telescope atop Mauna Kea, Hawaii, shows galaxies and stars with a range of different colors.

This new image also shows three different supermassive black holes in galaxies located in the merging clusters. The upper one shows that a jet powered by a supermassive black hole is connected to large swirls of radio emission. The team of astronomers thinks this connection provides important information about how the radio emission was produced.

This spinning, supermassive black hole is producing a rotating, tightly-wound magnetic funnel. The powerful electromagnetic fields associated with this structure have accelerated some of the inflowing gas away from the vicinity of the black hole in the form of an energetic, high-speed jet. Then, these accelerated particles in the jet were accelerated again when they encountered the shock waves from the galaxy cluster collision.

Jets from the two other supermassive black holes (see labeled version of image) are likely having the same effect of accelerating particles before they get a second boost from the shock waves. The jets from one of the black holes are too short to be seen in the labeled image.

[http://chandra.harvard.edu/photo/2017/a3411/]

The Hydra Cluster (Abell 1060 or Hydra A) is a galaxy cluster that contains 157 bright galaxies, appearing in the constellation Hydra. The cluster spans about ten million light years and has an unusually high proportion of dark matter. The cluster is part of the Hydra-Centaurus Supercluster located 158 million light years from earth. The cluster’s largest galaxies are elliptical galaxies NGC 3309 and NGC 3311 and the spiral galaxy NGC 3312 all having a diameter of about 150,000 light years. In spite of a nearly circular appearance on the sky, there is evidence in the galaxy velocities for a clumpy, three-dimensional distribution:

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

The Hydra Cluster of Galaxies

Two stars within our own Milky Way galaxy anchor the foreground of this cosmic snapshot. Beyond them lie the galaxies of the Hydra Cluster. In fact, while the spiky foreground stars are hundreds of light-years distant, the Hydra Cluster galaxies are over 100 million light-years away. Three large galaxies near the cluster center, two yellow ellipticals (NGC 3311, NGC 3309) and one prominent blue spiral (NGC 3312), are the dominant galaxies, each about 150,000 light-years in diameter. An intriguing overlapping galaxy pair cataloged as NGC 3314 is just above and left of NGC 3312. Also known as Abell 1060, the Hydra galaxy cluster is one of three large galaxy clusters within 200 million light-years of the Milky Way. In the nearby universe, galaxies are gravitationally bound into clusters which themselves are loosely bound into superclusters that in turn are seen to align over even larger scales. At a distance of 100 million light-years this picture would be about 1.3 million light-years across.

[https://apod.nasa.gov/apod/ap120512.html]

The Sigma Hydrids are a very active meteor shower with an unknown parent body in Hydra. It peaks on December 6:

The Sigma Hydrids meteor shower takes place within the boundaries constellation of the Hydrus. The meteor shower occurs between Dec 03 - Dec 15, with the peak occurring on Dec 12 every year.

The closest star to the radiant point of the meteor shower is Minchir. The coordinates can also be determined by the Right Ascension (123.2) and the Declination (3).

The Zenith Hourly Rate or how many you expect to see during the hour is 3. The ZHR can radically increase if the comet or associated object is close by. The speed/velocity of the Meteor Shower particles is 59 km/s. The population index of the meteor shower is 3. The population index refers to the magnitude distribution of the meteorites, the smaller the index, the brighter the meteors are, the higher, the dimmer the meteors are. For this particular meteor shower, bright meteors are more frequent.

[https://www.universeguide.com/meteorshower/sigmahydrids]

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

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