Serpens

[http://www.astronomytrek.com/star-constellation-facts-serpens/]

Serpens constellation lies in the northern hemisphere. Its name means ‘serpent’ in Latin. Serpens is the 23rd constellation in size, occupying an area of 637 square degrees. Serpens Caput, the western part of the constellation, representing the serpent’s head, is located in the third quadrant of the northern hemisphere (NQ3). Serpens Cauda, the eastern part, representing the serpent’s tail, is found in the third quadrant of the southern hemisphere (SQ3). The constellation can be seen at latitudes between +80° and -80°. The constellations bordering Serpens Caput are Boötes, Corona Borealis, Hercules, Libra, Ophiuchus and Virgo. The constellations bordering Serpens Cauda are Aquila, Ophiuchus, Sagittarius and Scutum.

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

Serpens held by Ophiuchus, as depicted in Urania’s Mirror, a set of constellation cards published in London c. 1825. Above the tail of the serpent is the now-obsolete constellation Taurus Poniatovii while below it is Scutum.

Serpens is the only one of the 88 modern constellations to be split into two disconnected regions in the sky: Serpens Caput (the head) and Serpens Cauda (the tail). The constellation is also unusual in that it depends on another constellation for context; specifically, it is being held by the Serpent Bearer Ophiuchus.

In Greek mythology, Serpens represents a snake held by the healer Asclepius. Represented in the sky by the constellation Ophiuchus, Asclepius once killed a snake, but the animal was subsequently resurrected after a second snake placed a revival herb on it before its death. As snakes shed their skin every year, they were known as the symbol of rebirth in ancient Greek society, and legend says Asclepius would revive dead humans using the same technique he witnessed. Although this is likely the logic for Serpens’ presence with Ophiuchus, the true reason is still not fully known. Sometimes, Serpens was depicted as coiling around Ophiuchus, but the majority of atlases showed Serpens passing either behind Ophiuchus' body or between his legs.

In some ancient atlases, the constellations Serpens and Ophiuchus were depicted as two separate constellations, although more often they were shown as a single constellation. One notable figure to depict Serpens separately was Johann Bayer; thus, Serpens' stars are cataloged with separate Bayer designations from those of Ophiuchus. When Eugène Delporte established modern constellation boundaries in the 1920s, he elected to depict the two separately. However, this posed the problem of how to disentangle the two constellations, with Deporte deciding to split Serpens into two areas- the head and the tail- separated by the continuous Ophiuchus. These two areas became known as Serpens Caput and Serpens Cauda, caput being the Latin word for head and cauda the Latin word for tail.

In Chinese astronomy, most of the stars of Serpens represented part of a wall surrounding a marketplace, known as Tianshi, which was in Ophiuchus and part of Hercules. Serpens also contains a few Chinese constellations. Two stars in the tail represented part of Shilou, the tower with the market office. Another star in the tail represented Liesi, jewel shops. One star in the head (Mu Serpentis) marked Tianru, the crown prince's wet nurse, or sometimes rain.

There were two ‘serpent’ constellations in Babylonian astronomy, known as Mušḫuššu and Bašmu. It appears that Mušḫuššu was depicted as a hybrid of a dragon, a lion and a bird, and loosely corresponded to Hydra. Bašmu was a horned serpent (c.f. Ningishzida) and roughly corresponds to the Ὄφις constellation of Eudoxus of Cnidus on which the Ὄφις (Serpens) of Ptolemy is based.

Constellations of Serpens, Scutum and Ophiuchus
[http://www.davidmalin.com/fujii/source/Ser.html]

[http://www.dibonsmith.com/ser_con.htm]

Alpha Serpentis, also named Unukalhai, is a double star in the head (Serpens Caput) of the equatorial constellation of Serpens. With an apparent visual magnitude of 2.6, this star is the brightest in the constellation and it can be viewed with the naked eye from most of the Earth. Parallax measurements yield an estimated distance of about 74 light-years (23 parsecs) from the Sun.

Alpha Serpentis is a giant star with a stellar classification of K2 III, having consumed the hydrogen at its core and evolved away from the main sequence. Its radius is about 12 times the radius of the Sun. The effective temperature of the outer envelope is 4,498 K, giving it an orange hue that is characteristic of a K-type star. This star is radiating about 38 times the luminosity of the Sun.

A magnitude +11.8 companion is at an angular separation of 58 arcseconds from Alpha Serpentis, while a 13th magnitude star lies 2.3 arcminutes distant.

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

Eta Serpentis is the second brightest star in the constellation Serpens. It lies in Serpens Cauda, the snake’s tail. The star has an apparent visual magnitude of 3.260, making it visible to the naked eye. It’s distance is 60.5 light-years (18.5 parsecs) from the Earth.

This star is larger than the Sun, with twice the mass and almost six times the radius. The spectrum matches a stellar classification of K0 III-IV, with the luminosity class of III-IV corresponding to an evolved star that lies between the subgiant and giant stages. The expanded outer envelope star is radiating about 19 times the luminosity of the Sun at an effective temperature of 4,890 K. At this temperature, it has an orange hue typical of a K-type star. Eta Serpentis displays solar-like oscillations with a period of 0.09 days.

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

Mu Serpentis is located in the body of Serpens and marks the lower part of Serpens Caput. Mu Serpentis is a white A-type main sequence dwarf with an apparent magnitude of +3.54. It is the third brightest star in Serpens, approximately 156 light years from Earth.

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

Beta, Gamma, and Iota Serpentis form a distinctive triangular shape marking the head of the snake, with Kappa Serpentis being roughly midway between Gamma and Iota. The brightest of the four with an apparent magnitude of roughly 3.67, Beta Serpentis is a white main-sequence star roughly 160 parsecs distant.

Rendering of NN Serpentis system

NN Serpentis (NN Ser) is an eclipsing post-common envelope binary system approximately 1670 light-years away. The system comprises an eclipsing white dwarf and red dwarf. The two stars orbit each other every 0.13 days.

In late 2009 and 2010, researchers suggested that the eclipse timing variations are caused by two gas giant planets. The more massive gas giant is about 6 times the mass of Jupiter and orbits the binary star every 15.5 years, the other orbits every 7.75 years and is about 1.6 times the mass of Jupiter.

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

An artist’s rendering of the Oort cloud and the Kuiper belt

Gliese 710 is a star in the constellation Serpens Cauda with an apparent visual magnitude of 9.69. It has a stellar classification of K7 Vk, which means it is a main sequence star that is generating energy through the thermonuclear fusion of hydrogen at its core. (The suffix ‘k’ indicates that the spectrum shows absorption lines from interstellar matter.) The mass of this star is about 60% of the Sun’s mass and it has an estimated 67% of the Sun’s radius. It is a suspected variable star that may vary in magnitude from 9.65- 9.69.

This star is currently about 63.8 light-years (19.6 parsecs) from Earth, but its proper motion, distance, and radial velocity indicate that it will approach within a very small distance- perhaps under one light year- from the Sun within 1.4 million years, based on past and current Hipparcos data. At closest approach it will be a first-magnitude star about as bright as Antares.

[https://en.wikipedia.org/wiki/Gliese_710]

This is a star- forming region in Serpens Cauda:

Stars forming in Serpens

Stars are forming in a dense molecular cloud a mere 1,000 light-years away in the constellation Serpens Cauda (The Serpent’s Tail). At that estimated distance, this sharp, near-infrared close-up of the active Serpens star-forming region spans about 2 arcminutes or just over half a light-year. Though such near-infrared observations can be made by mountain-top telescopes with specialized detectors, near-infrared light has too long a wavelength to be visible to the eye. This view was recorded with a sensitive camera, HAWK-I (High Acuity, Wide field K-band Imaging), just commissioned at the Paranal Observatory in Chile. Intended to illustrate HAWK-I’s impressive capabilities, the tantalizing image highlights reddish young stars and protostars, likely up to a few million years old, emerging from the nebular gas and dust.

[https://apod.nasa.gov/apod/ap070831.html]

The star cluster M16 is found within the Eagle Nebula in Serpens Cauda:

M16 and the Eagle Nebula

A star cluster around 2 million years young, M16 is surrounded by natal clouds of dust and glowing gas also known as The Eagle Nebula. This beautifully detailed image of the region includes cosmic sculptures made famous in Hubble Space Telescope close-ups of the starforming complex. Described as elephant trunks or Pillars of Creation, dense, dusty columns rising near the center are light-years in length but are gravitationally contracting to form stars. Energetic radiation from the cluster stars erodes material near the tips, eventually exposing the embedded new stars. Extending from the left edge of the frame is another dusty starforming column known as the Fairy of Eagle Nebula. M16 and the Eagle Nebula lie about 7,000 light-years away, an easy target for binoculars or small telescopes in a nebula rich part of the sky toward the split constellation Serpens Cauda (the tail of the snake).

[https://apod.nasa.gov/apod/ap140607.html]

Seyfert’s Sextet is a group of galaxies in Serpens Caput:

Seyfert’s Sextet

What will survive this battle of the galaxies? Known as Seyfert's Sextet, this intriguing group of galaxies lies in the head portion of the split constellation of the Snake (Serpens). The sextet actually contains only four interacting galaxies, though. Near the center of this Hubble Space Telescope picture, the small face-on spiral galaxy lies in the distant background and appears only by chance aligned with the main group. Also, the prominent condensation on the upper left is likely not a separate galaxy at all, but a tidal tail of stars flung out by the galaxies' gravitational interactions. About 190 million light-years away, the interacting galaxies are tightly packed into a region around 100,000 light-years across, comparable to the size of our own Milky Way galaxy, making this one of the densest known galaxy groups. Bound by gravity, the close-knit group may coalesce into a single large galaxy over the next few billion years.

[https://apod.nasa.gov/apod/ap131210.html]

Hoag’s Object is a ring galaxy in the constellation Serpens:

Hoag’s Object: A strange ring galaxy

Is this one galaxy or two? This question came to light in 1950 when astronomer Art Hoag chanced upon this unusual extragalactic object. On the outside is a ring dominated by bright blue stars, while near the center lies a ball of much redder stars that are likely much older. Between the two is a gap that appears almost completely dark. How Hoag's Object formed remains unknown, although similar objects have now been identified and collectively labeled as a form of ring galaxy. Genesis hypotheses include a galaxy collision billions of years ago and the gravitational effect of a central bar that has since vanished. The above photo taken by the Hubble Space Telescope in July 2001 revealed unprecedented details of Hoag’s Object. More recent observations in radio waves indicate that Hoag’s Object has not accreted a smaller galaxy in the past billion years. Hoag’s Object spans about 100,000 light years and lies about 600 million light years away toward the constellation of the Snake (Serpens). Coincidentally, visible in the gap (at about one o'clock) is yet another ring galaxy that likely lies far in the distance.

[https://apod.nasa.gov/apod/ap130728.html]

M5 is a globular star cluster in the constellation Serpens:

Hubble’s Messier 5

“Beautiful Nebula discovered between the Balance [Libra] & the Serpent [Serpens] ...” begins the description of the 5th entry in 18th century astronomer Charles Messier’s famous catalog of nebulae and star clusters. Though it appeared to Messier to be fuzzy and round and without stars, Messier 5 (M5) is now known to be a globular star cluster, 100,000 stars or more, bound by gravity and packed into a region around 165 light-years in diameter. It lies some 25,000 light-years away. Roaming the halo of our galaxy, globular star clusters are ancient members of the Milky Way. M5 is one of the oldest globulars, its stars estimated to be nearly 13 billion years old. The beautiful star cluster is a popular target for Earthbound telescopes. Of course, deployed in low Earth orbit on April 25, 1990, the Hubble Space Telescope has also captured its own stunning close-up view that spans about 20 light-years across the central region of M5. Even close to its dense core the cluster’s aging red and blue giant stars and rejuvenated blue stragglers stand out in yellow and blue hues in the sharp color image.

[https://apod.nasa.gov/apod/ap171104.html]

Lynds Dark Nebula 183 is a molecular cloud in Serpens Caput:

Lynds Dark Nebula 183

Beverly Lynds Dark Nebula 183 lies a mere 325 light-years away, drifting high above the plane of our Milky Way Galaxy. Obscuring the starlight behind it when viewed at optical wavelengths, the dark, dusty molecular cloud itself seems starless. But far infrared explorations reveal dense clumps within, likely stars in the early stages of formation as enhanced regions of the cloud undergo gravitational collapse. One of the closest molecular clouds, it is seen toward the constellation Serpens Caput. This sharp cosmic cloud portrait spans about half a degree on the sky. That’s about 3 light-years at the estimated distance of Lynds Dark Nebula 183.

[https://apod.nasa.gov/apod/ap171021.html]

Arp 220 is the result of a collision between two galaxies which are now in the process of merging:

[https://en.wikipedia.org/wiki/Arp_220]

Arp 220

Arp 220 appears to be a single, odd-looking galaxy, but is in fact a nearby example of the aftermath of a collision between two spiral galaxies. It is the brightest of the three galactic mergers closest to Earth, about 250 million light-years away in the constellation of Serpens, the Serpent. The collision, which began about 700 million years ago, has sparked a cracking burst of star formation, resulting in about 200 huge star clusters in a packed, dusty region about 5,000 light-years across (about 5 percent of the Milky Way's diameter). The amount of gas in this tiny region equals the amount of gas in the entire Milky Way Galaxy. The star clusters are the bluish-white bright knots visible in the Hubble image. Arp 220 glows brightest in infrared light and is an ultraluminous infrared galaxy. Previous Hubble observations, taken in the infrared at a wavelength that looks through the dust, have uncovered the cores of the parent galaxies 1,200 light-years apart. Observations with NASA’s Chandra X-ray Observatory have also revealed X-rays coming from both cores, indicating the presence of two supermassive black holes. Arp 220 is the 220th galaxy in Arp’s Atlas of Peculiar Galaxies.

This image is part of a large collection of 59 images of merging galaxies taken by the Hubble Space Telescope and released on the occasion of its 18th anniversary on 24th April 2008.

[https://www.spacetelescope.org/images/heic0810bf/]

At the center of Arp 220 a hyper-active super-massive black hole has been discovered:

Herschel galaxy survey: Overfed black holes shut down galactic star-making

A new study has shown that galaxies with the most powerful, active, supermassive black holes at their cores produce fewer stars than galaxies with less active black holes. Researchers compared infrared readings from the Hershel Space Observatory with X-rays streaming from the active central black holes in a survey of 65 galaxies, measured by NASA’s Chandra X-ray Observatory.

At lower intensities, the black holes' brightness and star formation increased in sync. However, star formation dropped off in galaxies with the most energetic central black holes. Astronomers think inflows of gas fuel new stars and supermassive black holes. Feed a black hole too much, however, and it starts spewing radiation into the galaxy that prevents raw material from coalescing into new stars.

Supermassive black holes are believed to reside in the hearts of all large galaxies. When gas falls upon these monsters, the materials are accelerated and heated around the black hole, releasing great torrents of energy. In the process, active black holes often generate colossal jets that blast out twin streams of heated matter.

Inflows of gas into a galaxy also fuel the formation of new stars. In a new study of distant galaxies, Herschel helped show that star formation and black hole activity increase together, but only up to a point. Astronomers think that if an active black hole flares up too much, it starts spewing radiation that prevents raw material from coalescing into new stars.

This artistically modified image of the local galaxy Arp 220, captured by the Hubble Space Telescope, helps illustrate the Herschel results. The bright core of the galaxy, paired with an overlaid artist’s impression of jets emanating from it, indicates that the central black hole's activity is intensifying. As the active black hole continues to rev up, the rate of star formation will, in turn, be tamped down in the galaxy. Astronomers want to further study how star formation and black hole activity are intertwined.

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

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

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