Double star system in the constellation Hydra
Delta Hydrae ,
Latinized from δ Hydrae, is a
double star in the equatorial
constellation of
Hydra . It is visible to the naked eye with an
apparent visual magnitude of 4.146.
[2] Based upon an annual
parallax shift of 20.34
mas , it is located about 160
light years from the
Sun .
This is a
double star
[10] with an angular separation of 2.6± 0.1 arc second along a
position angle of 265.1°± 1.0° , as of 2003.
[11] The brighter component is an
A-type main sequence star with a
stellar classification of A1 Vnn.
[3] 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.
[3] It has an estimated 2.88
[6] times the
mass of the Sun and 2.7
[7] times the
Sun's radius .
[7] The star is about 244 million years old and it radiates 42.7
[8] times the
solar luminosity from its
outer atmosphere at an
effective temperature of 11,055 K.
[6]
The companion has a visual magnitude of 11.15.
[10]
X-ray emissions have been detected from this location in space, which may be coming from a companion star.
[11]
Name and etymology
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 .
[12] This star, along with
ε Hya ,
ζ Hya ,
η Hya ,
ρ Hya and
σ Hya (Minchir), were
Ulugh Beg 's Min al Azʽal , "Belonging to the Uninhabited Spot".
[13]
According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars , Min al Azʽal or Minazal were the title for five stars :δ Hya as Minazal I ,
η Hya as Minazal II ,
ε Hya as Minazal III ,
ρ Hya as Minazal IV and
ζ Hya as Minazal V (exclude
σ Hya )
[14]
In
Chinese , 柳宿 (Liǔ Sù ), meaning
Willow (asterism) , refers to an asterism consisting of δ Hydrae,
σ Hydrae ,
η Hydrae ,
ρ Hydrae ,
ε Hydrae ,
ζ Hydrae ,
ω Hydrae and
θ Hydrae
[15] Consequently, δ Hydrae itself is known as 柳宿一 (Liǔ Sù yī , English: the First Star of Willow .)
[16]
The people of
Groote Eylandt called Unwala , "The Crab", for the star cluster including this star,
ε Hya ,
ζ Hya ,
η Hya ,
ρ Hya and
σ Hya (Minchir).
[17]
References
^
a
b
c
d
e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics , 474 (2): 653–664,
arXiv :
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Bibcode :
2007A&A...474..653V ,
doi :
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S2CID
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^
a
b
c
d Cousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards", South African Astronomical Observatory Circulars , 8 : 59,
Bibcode :
1984SAAOC...8...59C .
^
a
b
c
d Belle, G. T. (2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review , 20 (1): 51,
arXiv :
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2012A&ARv..20...51V ,
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^ de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics , 546 : 14,
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doi :
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S2CID
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^ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters , 38 (5): 331,
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S2CID
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^
a
b
c
d
e David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal , 804 (2): 146,
arXiv :
1501.03154 ,
Bibcode :
2015ApJ...804..146D ,
doi :
10.1088/0004-637X/804/2/146 ,
S2CID
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^
a
b
c Pasinetti Fracassini, L. E.; et al. (2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy & Astrophysics , 367 (2) (3rd ed.): 521–24,
arXiv :
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Bibcode :
2001A&A...367..521P ,
doi :
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S2CID
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^
a
b McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society , 427 (1): 343–57,
arXiv :
1208.2037 ,
Bibcode :
2012MNRAS.427..343M ,
doi :
10.1111/j.1365-2966.2012.21873.x ,
S2CID
118665352 .
^
"* del Hya" .
SIMBAD .
Centre de données astronomiques de Strasbourg . Retrieved 2017-01-03 .
^
a
b Mason, B. D.; et al. (2014),
"The Washington Visual Double Star Catalog" , The Astronomical Journal , 122 (6): 3466,
Bibcode :
2001AJ....122.3466M ,
doi :
10.1086/323920 , retrieved 2015-07-22
^
a
b De Rosa, R. J.; et al. (July 2011), "The Volume-limited A-Star (VAST) survey - I. Companions and the unexpected X-ray detection of B6-A7 stars", Monthly Notices of the Royal Astronomical Society , 415 (1): 854–866,
arXiv :
1103.4363 ,
Bibcode :
2011MNRAS.415..854D ,
doi :
10.1111/j.1365-2966.2011.18765.x ,
S2CID
84181878 .
^ Knobel, E. B. (June 1895), "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket",
Monthly Notices of the Royal Astronomical Society , 55 : 429,
Bibcode :
1895MNRAS..55..429K ,
doi :
10.1093/mnras/55.8.429 .
^
Allen, R. H. (1963),
Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc, p.
249 ,
ISBN
0-486-21079-0 , retrieved 2010-12-12 .
^
Jack W. Rhoads - Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars , Jet Propulsion Laboratory, California Institute of Technology; November 15, 1971
^ (in Chinese) 中國星座神話 , written by 陳久金. Published by 台灣書房出版有限公司, 2005,
ISBN
978-986-7332-25-7 .
^ (in Chinese)
AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 28 日
^
Helaine Selin , ed., Encyclopaedia of the history of science, technology, and medicine in non-western cultures , Dordrecht, Kluwer Academic Publishers, 1997,
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External links
Kaler, James B. (April 13, 2012),
"Delta Hydrae" , STARS , University of Illinois, retrieved 2017-01-03 .