Serpens constellation lies in the northern hemisphere. Its name means “the serpent” in Latin. Serpens is one of the Greek constellations, first catalogued by the Greek astronomer Ptolemy in the 2nd century.
The constellation is divided into two parts by Ophiuchus, the snake bearer: Serpens Caput, representing the serpent’s head, and Serpens Cauda, the serpent’s tail.
Serpens contains one of the best known nebulae in the sky, the Eagle Nebula (Messier 16), which in turn contains the Pillars of Creation, a star-forming region famously imaged by Hubble. Other notable deep sky objects in the constellation include the large globular cluster Messier 5, the emission nebula IC 4703, Seyfert’s Sextet of galaxies, the ring galaxy known as Hoag’s Object, the Red Square Nebula, and the Serpens South star cluster.
Facts, location and map
Serpens is the 23rd constellation in size, occupying an area of 637 square degrees. It is one of the 15 equatorial constellations. 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.
The constellation name Serpens is pronounced /ˈsɜːrpɛnz/. In English, the constellation is known as the Serpent. The genitive form of Serpens, used in star names, is Serpentis (pronunciation: /sərˈpɛntɪs/). The three-letter abbreviation, adopted by the International Astronomical Union (IAU) in 1922, is Ser.
Serpens has one star brighter than magnitude 3.00 and two stars located within 10 parsecs (32.6 light years) of Earth. The brightest star in the constellation is Alpha Serpentis, also known by its traditional name, Unukalhai, with an apparent magnitude of 2.63. The nearest star is GJ 1224 (spectral class M4.5V), a flare star located at a distance of 24.60 light years from Earth.
Serpens contains more than 15 stars with known planets. These are Omega Serpentis (spectral class G8III), HD 168443 (G5IV), HD 142245 (K0), HD 168746 (G5V), HD 175541 (G8IV), COROT-11 (F6V), COROT-28 (G8/9IV), COROT-9 (G3V), COROT-33 (G9V), COROT-27 (G2), COROT-23 (F9/G0V), COROT-16 (G5V), and COROT-17 (G5V).
The star NN Serpentis has two gas giant planets, and the stars HAT-P-45 and HAT-P-46 each have two transiting planets. The pulsar PSR J1719-1438 has a planet-sized companion that is made primarily of carbon and very dense, which earned it the nickname the Diamond Planet. The star HD 136118 has a red dwarf companion previously thought to be a planet.
Serpens contains five named stars. The names of stars that have been officially approved by the International Astronomical Union (IAU) are Alasia, Alya, Gudja, Kaveh, and Unukalhai.
Serpens belongs to the Hercules family of constellations, along with Aquila, Ara, Centaurus, Corona Australis, Corvus, Crater, Crux, Cygnus, Hercules, Hydra, Lupus, Lyra, Ophiuchus, Sagitta, Scutum, Sextans, Triangulum Australe and Vulpecula.
Serpens contains two Messier objects – Messier 5 (M5, NGC 5904) and Messier 16 (M16, NGC 6611, Eagle Nebula). There are two meteor showers associated with the constellation, the Omega Serpentids, peaking on December 26, and the Sigma Serpentids, peaking on December 27.
Serpens Caput map by IAU and Sky&Telescope magazine
Serpens Cauda map by IAU and Sky&Telescope magazine
Serpens myth
In Greek mythology, Serpens constellation represents a giant snake held by the healer Asclepius, represented by Ophiuchus constellation. Asclepius is usually depicted holding the top half of the snake in his left hand and the tail in his right hand.
Asclepius was the son of the god Apollo who was said to be able to bring people back to life with his healing powers. In one of the stories, he did away with a snake and saw it be brought back to life by a herb that another snake placed on it. It was said that Asclepius later used the same technique.
The brightest star in the constellation, Unukalhai (Alpha Serpentis), represents the serpent’s neck, and Alya (Theta Serpentis) marks the tip of the snake’s tail.
Serpens constellation dates back to Babylonian times. The Babylonians had two snake constellations. One represented a hybrid of a dragon, lion and bird and roughly corresponded to the constellation we know as Hydra, the water snake.
The other Babylonian constellation, called Bašmu, was depicted as a horned serpent, and loosely corresponded to the constellation Ὄφις, created by the Greek astronomer Eudoxus of Cnidus in the 4th century BC, on which Ptolemy’s Serpens constellation was based.
Serpens stars
Unukalhai – α Serpentis (Alpha Serpentis)
Alpha Serpentis is the brightest star in the constellation. It has an apparent magnitude of 2.623 and is approximately 74 light years distant from the Sun. It is a double star located in the serpent’s head, Serpens Caput.
The primary component in the system is an orange giant with the stellar classification of K2 III. The star has a radius about 12 times solar and is 38 times more luminous than the Sun. The companion has a visual magnitude of 11.8 and is located at an angular separation of 58 seconds of arc. A 13th magnitude star can also be found in the vicinity, 2.3 arc minutes away.
The star’s traditional name, Unukalhai, is derived from the Arabic ‘Unuq al-Ħayyah, which means “the serpent’s neck.” The star is also sometimes known as Cor Serpentis, which is Latin for “the heart of the serpent.”
η Serpentis (Eta Serpentis)
Eta Serpentis is the second brightest star in the constellation. It is located in Serpens Cauda, the serpent’s tail. It is an orange star halfway between the subgiant and giant evolutionary stage. It has the stellar classification of K0 III-IV.
Eta Serpentis has an apparent magnitude of 3.260 and is approximately 60.5 light years distant from Earth. It has a mass double that of the Sun and a radius 5.897 times solar. It is 19 times more luminous than the Sun.
μ Serpentis (Mu Serpentis)
Mu Serpentis is a white main sequence dwarf with the stellar classification of A0V. It has an apparent magnitude of 3.54 and is about 156 light years distant from the solar system. It is the third brightest star in Serpens. It is located in Serpens Caput, the serpent’s head.
ξ Serpentis (Xi Serpentis)
Xi Serpentis is a triple star system about 105 light years from Earth. It has a visual magnitude of 3.54. The primary component in the system is a yellow-white giant with the stellar classification F0IIIp. It is a spectroscopic binary star with an orbital period of 2.29 days. The third component in the system is a 13th magnitude star located 25 arc seconds away from the main pair.
β Serpentis (Beta Serpentis)
Beta Serpentis is another multiple star system. It is located in Serpens Caput. It has an apparent magnitude of 3.65 and is approximately 153 light years distant from Earth. The system is a member of the Ursa Major Moving Group of stars. It has the stellar classification of A3V.
The main component in the system is a white main sequence star. The star has two companions, one with a visual magnitude of 9.9 located 31 arc seconds from the primary star, and another with a magnitude of 10.7, 201 arc seconds from the primary.
ε Serpentis (Epsilon Serpentis)
Epsilon Serpentis is another white main sequence dwarf, belonging to the spectral class A2Vm. It has an apparent magnitude of 3.71 and is 70.3 light years distant from Earth. The star is located in Serpens Caput. It has a radius 1.8 times solar and is 12 times more luminous than the Sun.
δ Serpentis (Delta Serpentis)
Delta Serpentis is another star system in Serpens Caput. It has a combined apparent magnitude of 3.80 and is about 210 light years distant from the solar system.
Delta Serpentis is composed of two binary stars separated by 66 seconds of arc. The primary component is a yellow white subgiant star with a visual magnitude of 4.2. The star is classified as a Delta Scuti type variable, exhibiting variations in luminosity by 0.04 magnitudes with a period of 0.134 days. The star’s binary companion is also an F-type subgiant with an apparent magnitude of 5.2. The two stars are four arc seconds away from each other and have an orbital period of 3,200 years.
The second binary pair consists of a 14th magnitude star and a 15th magnitude binary companion separated by 4.4 seconds of arc.
γ Serpentis (Gamma Serpentis)
Gamma Serpentis is a yellow-white main sequence dwarf in Serpens Caput. It belongs to the spectral class F6 V. The star has an apparent magnitude of 3.85 and is approximately 36.3 light years distant from the solar system. It has a mass 1.30 times solar and a radius 1.55 times that of the Sun. It is 3.02 times more luminous than the Sun. The star is a suspected variable. It has two 10th magnitude optical companions.
κ Serpentis (Kappa Serpentis)
Kappa Serpens is a red giant of the spectral type M1III. It has an apparent magnitude of 4.09 and is about 348 light years distant from Earth. It is located in the serpent’s head, Serpens Caput.
ν Serpentis (Nu Serpentis)
Nu Serpentis is a binary star about 193 light years from Earth. It belongs to the spectral class A0/A1V. The primary component is a white main sequence dwarf with a visual magnitude of 4.32. The companion has a magnitude of 8.4 and is separated from the primary star by 46 seconds of arc.
λ Serpentis (Lambda Serpentis)
Lambda Serpentis is a yellow dwarf with the stellar classification of G0 V. It has an apparent magnitude of 4.43 and is 38.3 light years distant from the Sun. The star is a suspected variable. It has a mass 1.14 times that of the Sun and a radius 1.318 times solar. It is 1.94 times more luminous than the Sun.
The star is moving toward the Sun and in about 166,000 years it will come within 7.371 light years of the solar system.
Alya – θ Serpentis (Theta Serpentis)
Theta Serpentis is another multiple star system in Serpens. It has a combined apparent magnitude of 4.03 and is approximately 132 light years distant from the Sun. The star’s traditional name, Alya (sometimes Alga) is derived from the Arabic ’alyah, which means “the fat tail (of a sheep).”
Theta-1 and Theta-2 Serpentis are both main sequence dwarfs belonging to stellar classes A5V and A5Vn. The brighter component has a visual magnitude of 4.62 and Theta-2 has an apparent magnitude of 4.98. The stars are separated by 22 arc seconds in the sky, and have an orbital period of at least 14,000 years. The stars are 18 and 13 times more luminous than the Sun respectively, and both have masses and radii about twice solar and surface temperatures of 8,000 kelvins.
The third component in the system is a yellow star of the spectral type G5, with a visual magnitude of 6.71. It is separated from Theta-2 Serpentis by 7 arc minutes.
R Serpentis
R Serpentis is a red giant with the stellar classification of M7IIIe. It is a Mira variable, a pulsating variable star very red in colour that will expel its outer envelope to form a planetary nebula and become a white dwarf within a few million years.
R Serpentis has an apparent magnitude of 7.1 and is approximately 900 light years distant from the Sun.
χ Serpentis (Chi Serpentis)
Chi Serpentis is a white main sequence dwarf belonging to the spectral type A0p Sr. It has an apparent magnitude of 5.34 and is about 228 light years distant from the solar system.
The star is an Alpha-2 Canum Venaticorum type variable, a chemically peculiar star exhibiting magnitude variations by 0.03 over a period of 1.596 days.
τ Serpentis (Tau Serpentis)
Tau Serpentis is a Bayer designation shared by eight stars located in Serpens Caput. Tau-1 Serpentis (9 Serpentis) is a red giant belonging to the spectral class M1III. It has a visual magnitude that ranges from 5.13 to 5.20, and is approximately 900 light years distant from the Sun. The star has a radius 54 times solar and an absolute magnitude of -2.1.
Tau-2 Serpentis (12 Serpentis) is a blue-white main sequence star of the spectral type B9V. It has an apparent magnitude of 6.218 and is about 430 light years distant from Earth.
Tau-3 Serpentis (15 Serpentis) is a yellow giant with the stellar classification of G8III. It has an apparent magnitude of 6.108 and is approximately 410 light years distant from the solar system.
Tau-4 Serpentis (17 Serpentis) is a red bright giant belonging to the spectral class M5II-III. It has a visual magnitude that varies from 5.89 to 7.07 with a period of about 100 days, and is classified as a semi-regular variable star. The star is approximately 520 light years distant from the Sun.
Tau-5 Serpentis (18 Serpentis) is a yellow-white main sequence dwarf of the spectral type F3V. It has an apparent magnitude of 5.938 and is approximately 160 light years distant from Earth. It has a mass 1.52 times solar.
Tau-6 Serpentis (19 Serpentis) is a yellow giant star with the stellar classification of G8III. It has a visual magnitude of 6.00 and is about 450 light years distant from the solar system. The star is a member of the Ursa Major association. It has a radius 11 times solar.
Tau-7 Serpentis (22 Serpentis) is a white star belonging to the spectral class A2m. It has an apparent magnitude of 5.804 and is about 174 light years distant from Earth.
Tau-8 Serpentis (26 Serpentis) is a white main sequence dwarf with the stellar classification of A0V. It has an apparent magnitude of 6.144 and is approximately 320 light years distant from the solar system. It has a radius double that of the Sun.
HD 168443
HD 168443 is a yellow main sequence star with the stellar classification of G5IV. It has a visual magnitude of 6.92 and is approximately 123.5 light years distant from the solar system.
The star has a confirmed planet and a brown dwarf in its orbit. The planet has a mass 7.696 times that of Jupiter and completes an orbit around the star every 58.116 days, while the brown dwarf has 17.378 times Jupiter’s mass and an orbital period of 1,739.5 days.
HD 136118
HD 136118 is a yellow-white dwarf with an apparent magnitude of 6.94, about 171 light years from Earth. It has the stellar classification of F9V.
The American astronomer Debra Fischer discovered a massive planet orbiting the star in February 2002. The object turned out to be a brown dwarf with a mass 42 times that of Jupiter. The dwarf has an orbital period of 1,209 days.
Gliese 710
Gliese is an orange main sequence dwarf with the stellar classification of K7 Vk. It has an apparent magnitude of 9.69 and is approximately 63.8 light years distant from Earth. The star is a suspected variable, with variations in magnitude ranging from 9.65 to 9.69. It has about 60 percent of the Sun’s mass and 67 percent of the solar radius.
Within the next 1.4 million years, the star will approach the Sun within a very small distance, possibly under one light year. When it does, it will be as bright as Antares, the brightest star in Scorpius constellation. The star’s proximity will have the potential to send a shower of comets into the solar system.
Deep sky objects in Serpens
Messier 5 (M5, NGC 5904)
Messier 5 is a globular cluster in Serpens constellation. It has an apparent magnitude of 6.65 and is approximately 24,500 light years distant from Earth. The cluster is about 80 light years in radius and can be seen without binoculars in ideal conditions. It is one of the larger globular clusters known. The brightest stars in the cluster have an apparent magnitude of 12.2.
The cluster was discovered by the German astronomer Gottfried Kirch in 1702. Charles Messier discovered it in 1764, but thought it was a nebula. It was the German-born British astronomer William Herschel who was the first to resolve individual stars in the cluster – about 200 of them – in 1791. M5 in fact contains over 100,000 stars, with some estimates counting as many as 500,000. There are 105 known variable stars in the cluster, among them 97 known RR Lyrae variables.
The cluster has an estimated age of about 13 billion years, which makes it one of the older known clusters associated with our galaxy, the Milky Way.
Messier 5, image: Adam Block/Mount Lemmon SkyCenter/University of Arizona (CC BY-SA 3.0 US)
Eagle Nebula – Messier 16 (M16, NGC 6611)
The Eagle Nebula, sometimes also known as the Star Queen Nebula, is a nebula with a young open star cluster in Serpens. It was discovered by the Swiss astronomer Jean-Philippe de Chéseaux in 1745-1746. Its shape roughly resembles that of an eagle, which is how it got its name. Messier 16 is part of the diffuse emission nebula IC 4703.
This is a three-colour composite mosaic image of the Eagle Nebula (Messier 16, or NGC 6611), based on images obtained with the Wide-Field Imager camera on the MPG/ESO 2.2-metre telescope at the La Silla Observatory. At the centre, the so-called “Pillars of Creation” can be seen. This wide-field image shows not only the central pillars, but also several others in the same star-forming region, as well as a huge number of stars in front of, in, or behind the Eagle Nebula. The cluster of bright stars to the upper right is NGC 6611, home to the massive and hot stars that illuminate the pillars. The “Spire” — another large pillar — is in the middle left of the image. Image: ESO
The nebula contains the Pillars of Creation, a large region of star-formation that resembles a similar region in the Soul Nebula in Cassiopeia constellation.
The pillars were likely already destroyed in a supernova event about 8,000 to 9,000 years ago, but the image of the aftermath will not reach Earth for another 1,000 years or so.
NASA’s Hubble Space Telescope has revisited the famous Pillars of Creation, originally photographed in 1995, revealing a sharper and wider view of the structures in this visible-light image. Astronomers combined several Hubble exposures to assemble the wider view. The towering pillars are about 5 light-years tall. The dark, finger-like feature at bottom right may be a smaller version of the giant pillars. The new image was taken with Hubble’s versatile and sharp-eyed Wide Field Camera 3. The pillars are bathed in the blistering ultraviolet light from a grouping of young, massive stars located off the top of the image. Tails of gas can be seen bleeding off the pillars as the intense radiation heats and evaporates it into space. Denser regions of the pillars are shadowing material beneath them from the powerful radiation. Stars are being born deep inside the pillars, which are made of cold hydrogen gas laced with dust. The pillars are part of a small region of the Eagle Nebula, a vast star-forming region 6,500 light-years from Earth. Image: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
IC 4703
IC 4703 is a magnitude 8 diffuse emission nebula, and an active star forming region, associated with the Eagle Nebula. It is the nebula that surrounds Messier 16, which is in fact a cluster of stars.
IC 4703 is located in Serpens Cauda. The nebula is approximately 7,000 light years from Earth.
Seyfert’s Sextet – NGC 6027
Seyfert’s Sextet is a group of six galaxies in Serpens Caput constellation. Of these six, only four galaxies are physically related, while one is a background object, and another is in fact a separated part of one of the other galaxies that belongs to the group.
The four galaxies in the group are gravitationally interacting and will eventually merge to form a single giant elliptical galaxy. Seyfert’s Sextet is approximately 190 million light years distant from Earth. The group was named after the American astronomer Carl Keenan Seyfert, who discovered it in the 1950s. At the time, this was the most compact group of galaxies known.
NGC 6027 is a lenticular galaxy in Serpens. It is the brightest galaxy in Seyfert’s Sextet. The galaxy was discovered by the French astronomer Édouard Stephan in 1882. It has an apparent magnitude of 14.7 and is approximately 190 million light years distant from Earth.
Seyfert’s Sextet, image: NASA
NGC 6027a is a spiral galaxy with a visual magnitude of 14.9. The galaxy bears a strong resemblance to the Sombrero Galaxy (Messier 104) in Virgo constellation. NGC 6027b has an apparent magnitude of 15.3. It is classified as a S0 peculiar galaxy. NGC 6027c is another spiral galaxy. It has a visual magnitude of 16.7.
NGC 6027d is a spiral galaxy with an apparent magnitude of 16.5. It is not interacting with the other galaxies, but merely lies along the same line of sight, about 877 million light years from Earth. NGC 6027e is a tidal tail of NGC 6027. It has an apparent magnitude of 16.7.
Red Square Nebula – MWC 922
The Red Square Nebula is a bipolar nebula in Serpens notable for its square shape. It is one of the most symmetrical deep sky objects ever discovered. It is unclear how the central star, MWC 922, produces the nebula’s shape.
Red Square Nebula, image: NASA
Hoag’s Object
Hoag’s Object is a ring galaxy in Serpens Caput. It was named after the American astronomer Arthur Allen Hoag, who discovered it in 1950. The galaxy has an apparent magnitude of 16.0 and is approximately 600 million light years distant from the solar system.
It has an almost perfect ring structure formed by young hot blue stars surrounding the older galaxy nucleus. The inner core is about 17,000 light years in diameter, the surrounding ring is 75,000 light years across, and the galaxy’s outer diameter spans 121,000 light years.
An image of Hoag’s Object, a non-typical galaxy of the type known as a ring galaxy, discovered in 1950 by astronomer Art Hoag, who initially thought it to be a planetary nebula. Serendipitously, from the perspective of our solar system what appears to be an even more distant ring galaxy is plainly visible within the gap between this galaxy’s central body of mostly yellow stars and the outer ring of blue stars. Image: NASA
Serpens South star cluster
The Serpens South star cluster is a group of about 50 stars in Serpens constellation. The cluster is approximately 848 light years distant from Earth. 35 stars in the cluster are protostars, only starting to take shape.
Serpens South star cluster, image: NASA, JPL-Caltech, L. Allen (Harvard-Smithsonian CfA) & Gould’s Belt Legacy Team
NGC 6539
NGC 6539 is a globular star cluster in Serpens constellation. It has an apparent magnitude of 9.6 and is about 25,400 light years distant from Earth. The cluster was discovered by the Danish astronomer Theodor Brorsen in 1856.
Blinking Galaxy – NGC 6118
NGC 6118 is a grand design spiral galaxy in Serpens. It has an apparent magnitude of 12.42 and is approximately 82.9 million light years distant from the solar system. The galaxy is about 110,000 light years across, which makes it roughly the same size as the Milky Way.
NGC 6118 is a relatively faint object and not easy to observe with a small telescope. It got the nickname the Blinking Galaxy because it tends to come in and out of view depending on the eye position. A Type Ib supernova, SN2004dk, was discovered in the galaxy on August 1, 2004.
NGC 6118, a grand-design spiral galaxy, shines bright in this image, displaying its central bar and tight spiral arms from its home in the constellation of Serpens (The Snake). The galaxy is sometimes known to amateur astronomers as the “Blinking Galaxy” because this relatively faint, fuzzy object would appear to flick into existence when viewed through their telescopes in a certain orientation, and then suddenly disappear again as the eye position shifted. The brilliant blue star-forming regions of the galaxy, where hot young stars are born, are beautifully illuminated, even from over 80 million light-years away. Image: ESO
Arp 220
Arp 220 is a deep sky object formed by a collision of two galaxies that are currently in the process of merging. It is approximately 250 million light years distant and has an apparent magnitude of 13.9. It is classified as an Ultraluminous Infrared Galaxy (ULIRG), and is the nearest one of its kind to Earth. In October 2011, as many as 7 supernovae were observed in the galaxy at the same time.
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 ultra-luminous 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. Image: NASA, ESA, the Hubble Heritage (STScI, AURA)-ESA, Hubble Collaboration, and A. Evans (University of Virginia, Charlottesville, NRAO, Stony Brook University)
NGC 5964
NGC 5964 is another spiral galaxy in Serpens Caput. It has an apparent magnitude of 12.6.
NGC 5964, image based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA) and the Canadian Astronomy Data Centre (CADC/NRC/CSA).
NGC 5970
NGC 5970 is a large barred spiral galaxy in Serpens Caput. It has an apparent magnitude of 11.5 and is approximately 90 million light years distant from the solar system. It appears face-on when observed from Earth.
The galaxy has two smaller satellites. It lies about a degree to the southwest of the star Chi Serpentis.
NGC 5970, image: Sloan Digital Sky Survey
NGC 5962
NGC 5962 is a spiral galaxy in Serpens Caput. With an apparent magnitude of 11.3, it is the brightest galaxy in the Serpens galaxy cluster. The galaxy has a small central bulge and a relatively large core region. It seems to have three smaller satellites, all dwarf galaxies.
NGC 5962 was discovered by the German-born British astronomer William Herschel in 1784 using a Newtonian reflector telescope.
NGC 5962, image: Wikimedia Commons/Jschulman555 (CC BY-SA 3.0)
NGC 5921
NGC 5921 is a barred spiral galaxy in Serpens Caput. It has an apparent magnitude of 11.5. A supernova, SN 2001X, was observed in the galaxy in 2001.
NGC 5921, image: Adam Block, Mount Lemmon SkyCenter, University of Arizona (CC BY-SA 3.0 US)
Sh2-54
Sh2-54 is an extended bright emission nebula about 140 arcminutes in size. The core region of the nebula contains many infrared sources and many protostars, large masses formed as a result of contraction of gas that will eventually become stars. The older stars in the nebula are estimated to be 4-5 million years old, and form the open cluster NGC 6604.
The nebula is approximately 6,200 light years distant from the solar system. It is part of an extended nebulous region which also includes the Eagle Nebula and the Omega Nebula in Sagittarius constellation.
The emission nebula Sh2-54 glows brightly in this image from the SMARTS 0.9-meter Telescope at Cerro Tololo Inter-American Observatory, a Program of NSF’s NOIRLab. Gathering the fine details of this particular image required almost twenty minutes of observations and three different wavelength filters. Situated within the constellation of Serpens (The Serpent), Sh2-54 forms part of a much wider nebulosity which includes the famous Eagle Nebula. Image: CTIO/NOIRLab/NSF/AURA, acknowledgment: Image processing: Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin
NGC 6604
NGC 6604 is an open cluster in Serpens, located about 2 degrees to the north of the Eagle Nebula. It has an apparent magnitude of 6.5 and is approximately 5,500 light years distant.
3C 321
3C 321 is a pair of galaxies rotating around each other, located at a distance of 370 megaparsecs (1207 megalight-years) from Earth. The galaxies were the first example of one galaxy hitting another galaxy with a surge of energy. The energy is believed to emanate from the first galaxy’s supermassive black hole. The larger of the two galaxies, whose energy jet is directed toward the smaller galaxy, has been nicknamed the Death Star Galaxy.
This is a composite image showing a jet from the black hole at the center of the main galaxy (lower left) striking the edge of a companion galaxy (upper right). X-rays from Chandra (colored purple), visible and UV from Hubble (red & orange), and radio from the Very Large Array and MERLIN (blue). Image: NASA, ESA, D. Evans (Harvard-Smithsonian Center for Astrophysics), [X-ray: NASA/CXC/CfA/D.Evans et al.; Optical/UV: NASA/STScI; Radio: NSF/VLA/CfA/D.Evans et al., STFC/JBO/MERLIN]. Permission: PD-USGOV-NASA
NGC 5972
NGC 5972 (UGC 9946) is a spiral galaxy located at an approximate distance of 410 million light years from Earth. The galaxy has an apparent magnitude of 13.4 and occupies an area 1′.0 × 0.7 in size. It was discovered by the French astronomer Édouard Jean-Marie Stephan on June 29, 1880.
NGC 5972, image: Judy Schmidt (CC BY 2.0)
IC 4756
IC 4756 is an open star cluster in Serpens. It is approximately 1,300 light years distant from the solar system.
NGC 6535
NGC 6535 is a globular cluster located about 22,200 light years away. The cluster is about one light year across and has a visual magnitude of 9.3. It was discovered by the English astronomer John Russell Hind on April 26, 1852.
NGC 6535, image: NASA & ESA; acknowledgement: Gilles Chapdelaine
Palomar 5
Palomar 5 is another globular cluster in Serpens. It has an apparent magnitude of 11.75 and is approximately 76,000 light years distant from the solar system. The cluster is about 76 light years in radius.
It was discovered by the German astronomer Walter Baade in 1950 and then independently discovered by the American astronomer Albert George Wilson in 1955.
Westerhout 40
Westerhout 40 (W40) is a star-forming region 8 arc minutes in size, located at a distance of 1,420 light years from Earth. It is one of the nearest regions of formation of high-mass O- and B-type stars, but is difficult to observe in visible light because it is obscured by the molecular cloud in which the stars were formed.
Westerhout 40 contains an open cluster of about 520 young stars. The stars in the cluster’s central region are about 0.8 million years old, while those in the outer region are about 1.5 million years old.
This image taken by NASA’s Spitzer Space Telescope reveals the stellar nursery W40 (also known as Sh2-64) in infrared light. A young cluster of several hundred stars is located at the center of the nebula, and the stellar winds and radiation coming from these stars have blown bubbles in the surrounding gas. The expanding bubbles have produced the “butterfly” shape as seen in the image. Spitzer’s IRAC camera took this mid-infrared image in the bands 8.0 micron, 5.8 micron, 4.5 micron, and 3.6 micron, here represented as red, orange, green, and blue. Image: NASA/JPL-Caltech