Achernar

 

(ā'kərnär') , brightest star in the constellation Eridanus; Bayer designation α Eridani; 1992 position R.A. 1^h37.4^m, Dec. −57°16′. A bluish-white white star with apparent magnitude 0.51, it is one of the 10 brightest stars in the entire sky. Its distance is about 120 light-years, and its luminosity about 600 times that of the sun. Achernar is of spectral class B5 V. Its name is from the Arabic meaning “end of the river [Eridanus].”

Achernar

The position of Achernar.
Observation data Epoch J2000
Constellation	Eridanus
Right ascension	01h 37m 42.8s
Declination	−57° 14' 12"
Apparent magnitude (V)	0.50
Characteristics
Spectral type	B3 Vpe
U-B color index	−0.66
B-V color index	−0.20
Variable type	Lambda Eridani
Astrometry
Radial velocity (Rv)	16 km/s
Proper motion (μ)	RA: 88.02 mas/yr Dec.: −40.08 mas/yr
Parallax (π)	022.68 ± 0.57 mas
Distance	144 ± 4 ly (44 ± 1 pc)
Absolute magnitude (MV)	−2.77
Details
Mass	6–8 M☉
Radius	~10 R☉
Luminosity	3,311(bolometric) L☉
Temperature	14,510 K
Rotation	225–300 km/s
Age	1–5 × 108 years
Other designations
Alpha Eridani, α Eridani, HR 472, CD -57°334, HD 10144, SAO 232481, FK5 54, HIP 7588.

Achernar (α Eri / α Eridani / Alpha Eridani), sometimes spelled Achenar, is the brightest star in the constellation Eridanus and the eighth brightest star in the nighttime sky. It lies at the southern tip of the constellation.

Achernar is a bright blue star of six to eight solar masses. Although classified as a main sequence (dwarf) star, it is thousands of times brighter than the Sun. It is visible in the southern part of the night sky. It remains permanently below the horizon from many densely populated portions of Earth's northern hemisphere. From those Southern hemisphere countries from which it can be seen best, it is particularly conspicuous through being highest in the night sky in November when most other bright southern stars are skirting the horizon.

Until about March 2000, Achernar and Fomalhaut were the two first magnitude stars furthest in angular distance from any other first magnitude star in the celestial sphere. Antares, in the constellation of Scorpius, is now the most isolated first magnitude star.

It is the least spherical star in the Milky Way studied to date. Achernar spins so rapidly that its equatorial diameter is more than 50% greater than its polar diameter.

It is approximately 144 light years from the Solar System.

The name comes from the Arabic آخر النهر ākhir an-nahr "river's end".

It is known as 水委一 (Shuǐwěiyī, the First Star of the Crooked Running Water) in Chinese.

Fiction

• Achernar in fiction

External links

• Achernar at solstation.com
• Achernar at absoluteastronomy.com
• Surface temperature and synthetic spectral energy distributions for rotationally deformed stars

Donate to Wikimedia