Delta Hydrae, Latinized from δ Hydrae, is a

double star In observational astronomy, a double star or visual double is a pair of stars that appear close to each other as viewed from Earth, especially with the aid of optical telescopes. This occurs because the pair either forms a binary star (i.e. a bi ...

in the equatorial

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Hydra Hydra generally refers to: * Lernaean Hydra, a many-headed serpent in Greek mythology * ''Hydra'' (genus), a genus of simple freshwater animals belonging to the phylum Cnidaria Hydra or The Hydra may also refer to: Astronomy * Hydra (constel ...

. It is visible to the naked eye with an apparent visual magnitude of 4.146. Based upon an annual parallax shift of 20.34

mas Mas, Más or MAS may refer to: Film and TV * Más y Menos, fictional superhero characters, from the Teen Titans animated television series * Más (Breaking Bad), "Más" (''Breaking Bad''), a season three episode of ''Breaking Bad'' Songs * Más ( ...

, it is located about 160

light year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s from the Sun. This is a

with an angular separation of along a position angle of , as of 2003. The brighter component is an A-type main sequence star with a

stellar classification In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

of A1 Vnn. 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. It has an estimated 2.88 times the

mass of the Sun The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

and 2.7 times the Sun's radius. The star is about 244 million years old and it radiates 42.7 times the solar luminosity from its outer atmosphere at an

effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...

of 11,055 K. The companion has a visual magnitude of 11.15. X-ray emissions have been detected from this location in space, which may be coming from a companion star.

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''. 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". 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) In Chinese, (), 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 Consequently, δ Hydrae itself is known as (, en, the First Star of Willow.)
AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 28 日
/ref> 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).

References

External links

* {{DEFAULTSORT:Delta Hydrae A-type main-sequence stars Hydrae, Delta Hydra (constellation) Hydrae, 04 073262 042313 3401 Durchmusterung objects Minazal I