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Alphard

Alphard
Alphard is located in 100x100
Alphard

Alphard = α Hya (circled) in the constellation Hydra.
Observation data
Epoch J2000      Equinox J2000
Constellation Hydra
Right ascension 09h 27m 35.2433s
Declination −08° 39′ 30.969″
Apparent magnitude (V) +2.00
Characteristics
Spectral type K3 II-III
U−B color index +1.73
B−V color index +1.44
Astrometry
Radial velocity (Rv) −4.3 km/s
Proper motion (μ) RA: −14.49 mas/yr
Dec.: 33.25 mas/yr
Parallax (π) 18.40 ± 0.78mas
Distance 177 ± 8 ly
(54 ± 2 pc)
Absolute magnitude (MV) −1.69 ± 0.09
Details
Mass 3.03 ± 0.36 M
Radius 50.5 ± 4.0 R
Luminosity 780 ± 78 L
Surface gravity (log g) 1.54 cgs
Temperature 4,120 K
Metallicity [Fe/H] −0.06 dex
Rotation 2,991 days
Rotational velocity (v sin i) 1.1 km/s
Age (4.2 ± 1.6) × 108 years
Other designations
Alphard, Alfard, Alphart, Kalbelaphard, Cor Hydrae, 30 Hydrae, HR 3748, BD−08° 2680, HD 81797, SAO 136871, FK5 354, HIP 46390.

Alphard, also designated Alpha Hydrae (α Hydrae, abbreviated Alpha Hya, α Hya) is the brightest star in the constellation of Hydra.

α Hydrae (Latinised to Alpha Hydrae) is the star's Bayer designation.

The traditional name Alphard is from the Arabic الفرد (al-fard), "the solitary one", there being no other bright stars near it. It was also known as the "backbone of the Serpent" to the Arabs. In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, it was designated Soheil al Fard, which was translated into Latin as Soheil Solitarius, meaning the bright solitary one. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Alphard for this star. It is now so entered in the IAU Catalog of Star Names.

The European astronomer Tycho Brahe dubbed it Cor Hydræ, Latin for 'the heart of Hydra'.

In Chinese, 星宿 (Xīng Xiù), meaning Star, refers to an asterism consisting of Alphard, τ1 Hydrae, τ2 Hydrae, ι Hydrae, 26 Hydrae, 27 Hydrae, HD 82477 and HD 82428. Consequently, Alphard itself is known as 星宿一 (Xīng Xiù yī), "the First Star of Star". In ancient China it formed part of an asterism called the "red bird".


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Wikipedia

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