Achernar
From Wikipedia, the free encyclopedia
 The position of Achernar. |
|
| Observation data Equinox 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 |
| Metallicity | |
| Rotation | 225–300 km/s |
| Age | 1–5 × 108 years |
| Other designations | |
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.
