Serpens

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Serpens
Constellation
23rd)
Main stars11
Bayer/Flamsteed
stars
57
Stars with planets15
Stars brighter than 3.00m1
Stars within 10.00 pc (32.62 ly)2
Brightest starα Ser (Unukalhai) (2.63m)
Messier objects2
Meteor showers0
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 (

romanized: Óphis, lit.'the Serpent') is a constellation in the northern celestial hemisphere. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it remains one of the 88 modern constellations designated by the International Astronomical Union. It is unique among the modern constellations in being split into two non-contiguous parts, Serpens Caput (Serpent Head) to the west and Serpens Cauda (Serpent Tail) to the east. Between these two halves lies the constellation of Ophiuchus, the "Serpent-Bearer". In figurative representations, the body of the serpent is represented as passing behind Ophiuchus between Mu Serpentis in Serpens Caput and Nu Serpentis
in Serpens Cauda.

The brightest

ultraluminous infrared galaxy; and Hoag's Object, the most famous of the very rare class of galaxies known as ring galaxies
.

Part of the Milky Way's

Messier 16. The nebula measures 70 light-years by 50 light-years and contains the Pillars of Creation, three dust clouds that became famous for the image taken by the Hubble Space Telescope. Other striking objects include the Red Square Nebula, one of the few objects in astronomy to take on a square shape; and Westerhout 40, a massive nearby star-forming region consisting of a molecular cloud and an H II region
.

History

Serpens shown as a snake being held by Ophiuchus in Urania's Mirror.
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

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

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,[1] caput being the Latin word for head and cauda the Latin word for tail.[2]

In

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.[1]

There were two "serpent" constellations in

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.[3]

Characteristics

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.[1]

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

The pattern of stars in Serpens Caput seen with the naked eye, with a triangle marking the head and a line of stars extending down marking the upper body
The constellation Serpens (Caput) as it can be seen by the naked eye

Marking the heart of the serpent is the constellation's brightest star, Alpha Serpentis. Traditionally called Unukalhai,

spectral type K2III located approximately 23 parsecs distant with a visual magnitude of 2.630 ± 0.009,[8] meaning it can easily be seen with the naked eye even in areas with substantial light pollution. A faint companion is in orbit around the red giant star,[9] although it is not visible to the naked eye. Situated near Alpha is Lambda Serpentis, a magnitude 4.42 ± 0.05 star rather similar to the Sun[10] positioned only 12 parsecs away.[11] It has an exoplanet orbiting around it.[12] Another solar analog in Serpens is the primary of Psi Serpentis, a binary star[13] located slightly further away at approximately 14 parsecs.[14]

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]

Alpha² Canum Venaticorum variable situated midway between Delta and Beta which varies from its median brightness of 5.33 by 0.03 magnitudes over a period of approximately 1.5 days.[29] Chi Serpentis is a chemically peculiar star.[30]

The two stars in Serpens Caput that form part of the Snake's body below the heart are

slowly pulsating B star, which causes the system to vary by 0.03 magnitudes.[38]

Serpens Caput contains many

P Cygni profile,[41] where cold infalling gas on to the star creates redshifted hydrogen absorption lines next to the normal emission lines.[42]

Several stars in Serpens have been found to have

orange giant with a planet of at least 1.7 Jupiter-masses.[43] NN Serpentis, an eclipsing post-common-envelope binary consisting of a white dwarf and a red dwarf,[44] is very likely to have two planets causing variations in the period of the eclipses.[45] Although it does not have a planet, the solar analog HD 137510 has been found to have a brown dwarf companion within the brown-dwarf desert.[46]

pulsar wind of the pulsar, and the system's orbit has been found to vary slightly.[48]

Tail stars

The pattern of stars in Serpens Cauda seen with the naked eye, with a line of stars marking the tail
The constellation Serpens (Cauda) as it can be seen by the naked eye

The brightest star in the tail,

white giant with an excess of strontium.[51] Theta, forming the tip of the tail, is also a multiple system, consisting of two A-type main-sequence stars with a combined apparent magnitude of around 4.1 separated by almost half an arcminute.[9] There is also a third G-type star with a mass and radius similar to that of the Sun.[54]

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

UX Orionis star,[71] meaning that it shows irregular variations in its brightness.[72]

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

Ap secondary, although it is the only known spectroscopic binary to consist of a star with excess of mercury and manganese and an Ap star.[84]

South of the

far-ultraviolet spectral lines.[85] It is suspected that such Serpentids are in an earlier evolutionary phase, and will evolve first into double periodic variables and then classical Algol variables.[86] Also near the Eagle Nebula is the eclipsing Wolf–Rayet binary CV Serpentis, consisting of a Wolf–Rayet star and a hot O-type subgiant. The system is surrounded by a ring-shaped nebula, likely formed during the Wolf–Rayet phase of the primary.[87] The eclipses of the system vary erratically, and although there are two theories as to why, neither of them is completely consistent with current understanding of stars.[88]

Serpens Cauda contains a few

Eddington limit.[89] The system has also been found to approximately every 3 days brighten by around 3.5 K-band magnitudes, possibly due to the presence of a synchrotron jet.[90] Another low-mass X-ray binary, Serpens X-1, undergoes occasional X-ray bursts. One in particular lasted nearly four hours, possibly explained by the burning of carbon in "a heavy element ocean".[91]

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

Messier 5's central dense core of stars, containing a large number of stars packed into a small area
Messier 5, a globular cluster that can be seen with the naked eye under good conditions

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

magnetic dipole moments in neutrinos, which could shed light on some hypothetical particles such as the axion.[103] The brightest stars in Messier 5 are around magnitude 10.6,[104] and the globular cluster was first observed by William Herschel in 1791.[105]

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

LINER-type active galactic nucleus situated somewhat closer at a distance of 21 megaparsecs.[119] A type II supernova was observed in this galaxy in 2001 and was designated SN 2001X.[120] Fainter still are the spirals NGC 5964[121] and NGC 6118, with the latter being host to the supernova SN 2004dk.[122]

The yellow nucleus of Hoag's Object surrounded by a blue ring of stars
Hoag's Object, a galaxy in Serpens and a member of the very rare class known as ring galaxies.

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.

Seyfert 2 galaxy and the latter a LINER-type galaxy. Both are undergoing a burst of star formation triggered by the interaction.[124]

merge to form a large elliptical galaxy.[123] The radio source 3C 326 was originally thought to emanate from a giant elliptical galaxy. However, in 1990, it was shown that the source is instead a brighter, smaller galaxy a few arcseconds north.[125] This object, designated 3C 326 N, has enough gas for star formation, but is being inhibited due to the energy from the radio galaxy nucleus.[126]

A much larger galaxy cluster is the redshift-0.0354

cD galaxy at the center of Abell 2063.[128] The active galaxy at the center of MKW 3s—NGC 5920—appears to be creating a bubble of hot gas from its radio activity.[129] Near the 5th-magnitude star Pi Serpentis lies AWM 4, a cluster containing an excess of metals in the intracluster medium. The central galaxy, NGC 6051, is a radio galaxy that is probably responsible for this enrichment.[130] Similar to AWM 4, the cluster Abell 2052 has central cD radio galaxy, 3C 317. This radio galaxy is believed to have restarted after a period of inactivity less than 200 years ago.[131] The galaxy has over 40,000 known globular clusters, the highest known total of any galaxy as of 2002.[132]

A brilliant red galaxy on the left interacts with a blue galaxy on the right, forming the merging active galaxy pair 3C 321.
A composite image of 3C 321, a merging active galaxy pair

Consisting of two quasars with a separation of less than 5

lensed image, although it does have a true companion of its own.[134] An even stranger galaxy pair is 3C 321. Unlike the previous pair, the two galaxies making up 3C 321 are interacting with each other and are in the process of merging. Both members appear to be active galaxies; the primary radio galaxy may be responsible for the activity in the secondary by means of the former's jet driving material onto the latter's supermassive black hole.[135]

An example of

BL Lac object PG 1553+113 is a heavy emitter of gamma rays. This object is the most distant found to emit photons with energies in the TeV range as of 2007.[138] The spectrum is unique, with hard emission in some ranges of the gamma-ray spectrum in stark contrast to soft emission in others.[139] In 2012, the object flared in the gamma-ray spectrum, tripling in luminosity for two nights, allowing the redshift to be accurately measured as z = 0.49.[140]

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

star-forming region
in the Eagle Nebula made famous by this Hubble photograph

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,

Messier 16 lie around 5,700[144] light-years from Earth in the direction of the Galactic Center. The nebula measures 70 light-years by 50 light-years and contains the Pillars of Creation, three dust clouds that became famous for the image taken by the Hubble Space Telescope. The stars being born in the Eagle Nebula, added to those with an approximate age of 5 million years have an average temperature of 45,000 kelvins and produce prodigious amounts of radiation that will eventually destroy the dust pillars.[123] Despite its fame, the Eagle Nebula is fairly dim, with an integrated magnitude of approximately 6.0. The star-forming regions in the nebula are often evaporating gaseous globules; unlike Bok globules they only hold one protostar.[145]

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]

forbidden lines, likely due to the presence of a close binary.[156] East of Xi Serpentis is another planetary nebula, Abell 41, containing the binary star MT Serpentis at its center. The nebula appears to have a bipolar structure, and the axis of symmetry of the nebula has been found to be within 5° of the line perpendicular to the orbital plane of the stars, strengthening the link between binary stars and bipolar planetary nebulae.[157] On the other end of the stellar age spectrum is L483, a dark nebula which contains the protostar IRAS 18418-0440. Although classified as a class 0 protostar, it has some unusual features for such an object, such as a lack of high-velocity stellar winds, and it has been proposed that this object is in transition between class 0 and class I.[158] A variable nebula exists around the protostar, although it is only visible in infrared light.[159]

Bright blue stars in a large gold cloud of gas
Westerhout 40, one of the nearest sites of massive star formation

The

Serpens South protocluster was uncovered by NASA's Spitzer Space Telescope in the southern portion of the cloud,[164] and it appears that star formation is still continuing in the region.[165] Another site of star formation is the Westerhout 40 complex, consisting of a prominent HII region adjacent to a molecular cloud.[166] Located around 500 parsecs distant,[167] it is one of the nearest massive regions of star formation, but as the molecular cloud obscures the HII region, rendering it and its embedded cluster tough to see visibly, it is not as well-studied as others.[168] The embedded cluster likely contains over 600 stars above 0.1 solar masses,[169] with several massive stars, including at least one O-type star, being responsible for lighting the HII region and the production of a bubble.[167]

Despite the presence of the Milky Way, several active galaxies are visible in Serpens Cauda as well, such as

Kerr black hole.[171] It is possible that the quasar is undergoing a transition from an ultraluminous infrared galaxy to a classical radio-quiet quasar, but there are problems with this theory, and the object appears to be an exceptional object that does not completely lie within current classification systems.[170] Nearby is NRAO 530, a blazar that has been known to flare in the X-rays occasionally. One of these flares was for less than 2000 seconds, making it the shortest flare ever observed in a blazar as of 2004.[172] The blazar also appears to show periodic variability in its radio wave output over two different periods of six and ten years.[173]

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]

References

  1. ^ a b c d Ridpath, Ian. "Serpens". Star Tales. self-published. Retrieved 15 May 2014.
  2. ^ Arnold, Maurice (Toby). "Arnold's Glossary of Anatomy". Anatomy & Histology - Online Learning. The University of Sydney. Archived from the original on 2015-09-02. Retrieved 8 August 2015.
  3. .
  4. ^ a b Ridpath, Ian. "Constellations: Andromeda–Indus". Star Tales. self-published. Retrieved 1 April 2014.
  5. ^ a b "Serpens, Constellation Boundary". The Constellations. International Astronomical Union. Retrieved 20 April 2014.
  6. .
  7. .
  8. ^ "* Alpha Serpentis – Star in double system". SIMBAD. Retrieved 18 April 2014.
  9. ^
    S2CID 14878976
    .
  10. .
  11. ^ "* Lambda Serpentis – Star". SIMBAD. Retrieved 20 May 2014.
  12. S2CID 235186973
  13. .
  14. ^ "* Psi Serpentis – Double or multiple star". SIMBAD. Retrieved 21 June 2014.
  15. ^ "IAU Catalog of Star Names". International Astronomical Union. Retrieved 2018-09-17.
  16. ^ "* Beta Serpentis – Star in double system". SIMBAD. Retrieved 12 May 2014.
  17. ^ "* Beta Serpentis B – Star in double system". SIMBAD. Retrieved 12 May 2014.
  18. S2CID 119226823
    .
  19. ^ VSX (4 January 2010). "R Serpentis". AAVSO Website. American Association of Variable Star Observers. Retrieved 22 May 2014.
  20. ^ "* Gamma Serpentis – Variable star". SIMBAD. Retrieved 22 May 2014.
  21. .
  22. .
  23. .
  24. ^ "* Delta Serpentis – Double or multiple star". SIMBAD. Retrieved 18 May 2014.
  25. ^ "* Delta Serpentis B – Star in double system". SIMBAD. Retrieved 18 May 2014.
  26. ^ VSX (4 January 2010). "Delta Serpentis". AAVSO Website. American Association of Variable Star Observers. Retrieved 18 May 2014.
  27. ^ "* 16 Serpentis – Star". SIMBAD. Retrieved 24 May 2014.
  28. .
  29. ^ VSX (4 January 2010). "Chi Serpentis". AAVSO Website. American Association of Variable Star Observers. Retrieved 26 May 2014.
  30. .
  31. ^ "* Epsilon Serpentis – Star". SIMBAD. Retrieved 26 May 2014.
  32. ^ "* Mu Serpentis – Star". SIMBAD. Retrieved 26 May 2014.
  33. .
  34. .
  35. .
  36. .
  37. .
  38. ^ VSX; Otero, S. A (10 February 2012). "PT Serpentis". AAVSO Website. American Association of Variable Star Observers. Retrieved 28 May 2014.
  39. .
  40. ^ VSX; Otero, S. A (28 June 2012). "Tau4 Serpentis". AAVSO Website. American Association of Variable Star Observers. Retrieved 24 June 2014.
  41. .
  42. ^ Galactic Star and Planet Formation Research Group. "Lecture 7: The Collapse of Cores and Infall" (PDF). Department of Physics and Astronomy, University of Toledo. Retrieved 17 July 2015.
  43. S2CID 119248666
    .
  44. .
  45. .
  46. .
  47. .
  48. .
  49. .
  50. ^ a b "Xi Serpentis – Spectroscopic binary". SIMBAD. Retrieved 21 June 2014.
  51. S2CID 119476992
    .
  52. .
  53. . 40. See Table 3.
  54. ^ "Nu Serpentis – Star in double system". SIMBAD. Retrieved 20 June 2014.
  55. ^ "Omicron Serpentis – Variable Star of delta Sct type". SIMBAD. Retrieved 20 June 2014.
  56. ^ "Zeta Serpentis – Star". SIMBAD. Retrieved 20 June 2014.
  57. ^ "BD-12 4724 – Star in double system". SIMBAD. Retrieved 20 June 2014.
  58. ^ VSX (4 January 2010). "Omicron Serpentis". AAVSO Website. American Association of Variable Star Observers. Retrieved 20 June 2014.
  59. S2CID 120532937
    .
  60. ^ VSX; Osborne, W. (1 April 2014). "RT Serpentis". AAVSO Website. American Association of Variable Star Observers. Retrieved 28 May 2014.
  61. .
  62. .
  63. ^ "HD 169986 – Star in double system". SIMBAD. Retrieved 25 May 2014.
  64. ^ VSX (4 January 2010). "d Serpentis". AAVSO Website. American Association of Variable Star Observers. Retrieved 25 May 2014.
  65. ^ VSX (28 April 2010). "FH Serpentis". AAVSO Website. American Association of Variable Star Observers. Retrieved 23 June 2014.
  66. S2CID 1508384
    .
  67. .
  68. .
  69. .
  70. ^ VSX; Otero, S. A. (23 November 2011). "VV Serpentis". AAVSO Website. American Association of Variable Star Observers. Retrieved 28 May 2014.
  71. . Retrieved 8 August 2015.
  72. ^ VSX (4 January 2010). "MV Serpentis". AAVSO Website. American Association of Variable Star Observers. Retrieved 25 May 2014.
  73. .
  74. ^ "HR 7008 – Star in Cluster". SIMBAD. Retrieved 14 December 2014.
  75. .
  76. .
  77. .
  78. .
  79. .
  80. .
  81. ^ VSX (4 January 2010). "V411 Serpentis". AAVSO Website. American Association of Variable Star Observers. Retrieved 25 May 2014.
  82. .
  83. .
  84. .
  85. .
  86. .
  87. .
  88. .
  89. .
  90. .
  91. ^ Sky Catalogue 2000.0, Volume 2: Double Stars, Variable Stars, and Nonstellar Objects (edited by Alan Hirshfeld and Roger W. Sinnott, 1985), Chapter 3: Glossary of Selected Astronomical Names.
  92. ^ Sky and Telescope, November 1961, page 263.
  93. ^ Deep-Sky Name Index 2000.0 - Hugh C. Maddocks (Foxon-Maddocks Associates, 1991).
  94. S2CID 56269929
    .
  95. .
  96. .
  97. SEDS
    . Retrieved 16 December 2014.
  98. .
  99. .
  100. .
  101. .
  102. .
  103. . Retrieved 1 March 2021.
  104. ^ "William Herschel's Observations of the Messier Objects". www.messier.seds.org. Students for the Exploration and Development of Space. Retrieved 1 March 2021.
  105. S2CID 45284760
    .
  106. .
  107. .
  108. .
  109. .
  110. .
  111. .
  112. .
  113. ^ "NED results for object NGC 5962". NASA/IPAC Extragalactic Database. Retrieved 3 June 2015.
  114. S2CID 119085482
    .
  115. .
  116. . 85.
  117. ^ "NED results for object NGC 5921". NASA/IPAC Extragalactic Database. Retrieved 3 June 2015.
  118. .
  119. .
  120. .
  121. ^ .
  122. .
  123. .
  124. .
  125. .
  126. .
  127. .
  128. .
  129. .
  130. .
  131. .
  132. .
  133. .
  134. .
  135. .
  136. .
  137. .
  138. .
  139. .
  140. .
  141. .
  142. ^ Kuhn, Michael A.; Hillenbrand, Lynne A.; Sills, Alison; Feigelson, Eric D.; Getman, Konstantin V. (2018). "Kinematics in Young Star Clusters and Associations with Gaia DR2". The Astrophysical Journal. 870 (1): 32.
    S2CID 119328315
    .
  143. .
  144. ^ .
  145. .
  146. .
  147. .
  148. .
  149. .
  150. .
  151. .
  152. .
  153. ^ Plummer, A.; Otero, S. A. (27 March 2013). "MWC 922". AAVSO Website. American Association of Variable Star Observers. Retrieved 11 May 2014.
  154. ^ Otero, S. A.; Watson, C.; Wils, P. "Variable Star Type Designations in the VSX". AAVSO Website. American Association of Variable Star Observers. Retrieved 11 May 2014.
  155. S2CID 119310966
    .
  156. .
  157. .
  158. .
  159. .
  160. .
  161. .
  162. .
  163. .
  164. .
  165. ^ .
  166. .
  167. .
  168. ^ .
  169. .
  170. .
  171. .
  172. ^ Jenniskens, Peter (September 2012). "Mapping Meteoroid Orbits: New Meteor Showers Discovered". Sky & Telescope: 24.

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