Achernar
From Wikipedia, the free encyclopedia
 The position of Achernar. |
|
| Observation data Epoch J2000 |
|
|---|---|
| Constellation (pronunciation) |
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 | |
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 B-type star of six to eight solar masses lying approximately 144 light years away. Although classified as a main-sequence (dwarf) star, it is about 3,000 times more luminous than the Sun. Achernar is in the deep southern sky and never rises above 33°N. Achernar is best seen from the southern hemisphere in November; it is circumpolar below 33°S.
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.
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.
