Serpens
Constellation | |
23rd) | |
Main stars | 11 |
---|---|
Bayer/Flamsteed stars | 57 |
Stars with planets | 15 |
Stars brighter than 3.00m | 1 |
Stars within 10.00 pc (32.62 ly) | 2 |
Brightest star | α Ser (Unukalhai) (2.63m) |
Messier objects | 2 |
Meteor showers | 0 |
Bordering constellations | Serpens Caput: Corona Borealis Boötes Virgo Libra Ophiuchus Hercules Serpens Cauda: Aquila Ophiuchus Sagittarius Scutum |
Visible at latitudes between +80° and −80°. Best visible at 21:00 (9 p.m.) during the month of July. |
Serpens (
The brightest
Part of the Milky Way's
History
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.[1]
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
In
There were two "serpent" constellations in
Characteristics
Serpens is the only one of the
Serpens Caput is bordered by Libra to the south, Virgo and Boötes to the west, Corona Borealis to the north, and Ophiuchus and Hercules to the east; Serpens Cauda is bordered by Sagittarius to the south, Scutum and Aquila to the east, and Ophiuchus to the north and west. Covering 636.9 square degrees total, it ranks 23rd of the 88 constellations in size. It appears prominently in both the northern and southern skies during the Northern Hemisphere's summer.[4] Its main asterism consists of 11 stars, and 108 stars in total are brighter than magnitude 6.5, the traditional limit for naked-eye visibility.[4]
Serpens Caput's boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a 10-sided polygon, while Serpens Cauda's are defined by a 22-sided polygon. In the equatorial coordinate system, the right ascension coordinates of Serpens Caput's borders lie between 15h 10.4m and 16h 22.5m , while the declination coordinates are between 25.66° and −03.72°. Serpens Cauda's boundaries lie between right ascensions of 17h 16.9m and 18h 58.3m and declinations of 06.42° and −16.14°.[5] The International Astronomical Union (IAU) adopted the three-letter abbreviation "Ser" for the constellation in 1922.[5][6]
Features
Stars
Head stars
Marking the heart of the serpent is the constellation's brightest star, Alpha Serpentis. Traditionally called Unukalhai,
Beta, Gamma, and Iota Serpentis form a distinctive triangular shape marking the head of the snake, with Kappa Serpentis (the proper name is Gudja[15]) 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.[16] It is likely that a nearby 10th-magnitude star[17] is physically associated with Beta, although it is not certain.[18] The Mira variable R Serpentis, situated between Beta and Gamma, is visible to the naked eye at its maximum of 5th-magnitude, but, typical of Mira variables, it can fade to below magnitude 14.[19] Gamma Serpentis itself is an F-type subgiant located only 11 parsecs distant and thus is quite bright, being of magnitude 3.84 ± 0.05.[20] The star is known to show solar-like oscillations.[21] Iota Serpentis is a binary star system.[22]
The two stars in Serpens Caput that form part of the Snake's body below the heart are
Serpens Caput contains many
Several stars in Serpens have been found to have
Tail stars
The brightest star in the tail,
Lying near the boundary with Ophiuchus are Zeta, Nu, and Omicron Serpentis. All three are 4th-magnitude main-sequence stars, with Nu and Omicron being of spectral type A[55][56] and Zeta being of spectral type F.[57] Nu is a single star[9] with a 9th-magnitude visual companion,[58] while Omicron is a Delta Scuti variable with amplitude variations of 0.01 magnitudes.[59] In 1909, the symbiotic nova[60] RT Serpentis appeared near Omicron, although it only reached a maximum magnitude of 10.[61]
The star system
The star HR 6958, also known as MV Serpentis, is an Alpha2 Canum Venaticorum variable that is faintly visible to the naked eye.[73] The star's metal abundance is ten times higher than the Sun for most metals at the iron peak and up to 1,000 times more for heavier elements. It has also been found to contain excess silicon.[74] Barely visible to the naked eye is HD 172365,[75] a likely post-blue straggler in the open cluster IC 4756 that contains a large excess of lithium.[76] HD 172189, also located in IC 4756, is an Algol variable eclipsing binary[77] with a 5.70 day period. The primary star in the system is also a Delta Scuti variable, undergoing multiple pulsation frequencies, which, combined with the eclipses, causes the system to vary by around a tenth of a magnitude.[78]
As the
South of the
Serpens Cauda contains a few
Φ 332 (Finsen 332) is a tiny and difficult double-double star at 18:45 / +5°30', named Tweedledee and Tweedledum by South African astronomer William Stephen Finsen, who was struck by the nearly identical position angles and separations at the time of his 1953 discovery.[92][93][94] Gliese 710 is a star that is expected to pass very close to the Solar System in around 1.29 million years.[95][96][97]
Deep-sky objects
Head objects
As the galactic plane does not pass through this part of Serpens, a view to many galaxies beyond it is possible. However, a few structures of the Milky Way Galaxy are present in Serpens Caput, such as Messier 5, a
Another globular cluster is Palomar 5, found just south of Messier 5. Many stars are leaving this globular cluster due to the Milky Way's gravity, forming a tidal tail over 30000 light-years long.[106] It is over 11 billion years old.[107] It has also been flattened and distorted by tidal effects.[108]
The L134/L183 is a dark nebula complex that, along with a third cloud, is likely formed by fragments of a single original cloud located 36 degrees away from the galactic plane, a large distance for dark nebulae.[109] The entire complex is thought to be around 140 parsecs distant.[110] L183, also referred to as L134N, is home to several infrared sources, indicating pre-stellar sources[111] thought to present the first known observation of the contraction phase between cloud cores and prestellar cores.[112] The core is split into three regions,[113] with a combined mass of around 25 solar masses.[114]
Outside of the Milky Way, there are no bright deep-sky objects for amateur astronomers in Serpens Caput, with nothing else above 10th magnitude. The brightest is
Hoag's Object, located 600 million light-years from Earth, is a member of the very rare class of galaxies known as ring galaxies. The outer ring is largely composed of young blue stars while the core is made up of older yellow stars. The predominant theory regarding its formation is that the progenitor galaxy was a barred spiral galaxy whose arms had velocities too great to keep the galaxy's coherence and therefore detached.
A much larger galaxy cluster is the redshift-0.0354
Consisting of two quasars with a separation of less than 5
An example of
Several gamma-ray bursts (GRBs) have been observed in Serpens Caput, such as GRB 970111, one of the brightest GRBs observed. An optical transient event associated with this GRB has not been found, despite its intensity. The host galaxy initially also proved elusive, however it now appears that the host is a Seyfert I galaxy located at redshift z = 0.657.[141] The X-ray afterglow of the GRB has also been much fainter than for other dimmer GRBs.[142] More distant is GRB 060526 (redshift z = 3.221), from which X-ray and optical afterglows were detected. This GRB was very faint for a long-duration GRB.[143]
Tail objects
Part of the galactic plane passes through the tail, and thus Serpens Cauda is rich in deep-sky objects within the Milky Way galaxy. The Eagle Nebula and its associated star cluster,
North of Messier 16, at a distance of approximately 2000 parsecs, is the
Another open cluster in Serpens Cauda is IC 4756, containing at least one naked-eye star, HD 172365[149] (another naked-eye star in the vicinity, HD 171586, is most likely unrelated). Positioned approximately 440 parsecs distant,[150] the cluster is estimated to be around 800 million years old, quite old for an open cluster.[151] Despite the presence of the Milky Way in Serpens Cauda, one globular cluster can be found: NGC 6535, although invisible to the naked eye, can be made out in small telescopes just north of Zeta Serpentis. Rather small and sparse for a globular cluster,[152] this cluster contains no known RR Lyrae variables, which is unusual for a globular cluster.[153]
The
Despite the presence of the Milky Way, several active galaxies are visible in Serpens Cauda as well, such as
Meteor showers
There are two daytime meteor showers that radiate from Serpens, the Omega Serpentids and the Sigma Serpentids. Both showers peak between December 18 and December 25.[174]
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External links
- The Deep Photographic Guide to the Constellations: Serpens (Caput)
- The clickable Serpens (Caput)
- Media related to Serpens at Wikimedia Commons
- Warburg Institute Iconographic Database (medieval and early modern images of Serpens); more can be found under Serpentarius