Achernar
 The position of Achernar. | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 01h 37m 42.85s [1] |
| Declination | –57° 14′ 12.3″ [1] |
| Apparent magnitude (V) | 0.50 |
| Characteristics | |
| Spectral type | B3 Vpe [1] |
| U−B color index | −0.67[1] |
| B−V color index | −0.16 [1] |
| Variable type | Lambda Eridani |
| Astrometry | |
| Radial velocity (Rv) | 16 [1] km/s |
| Proper motion (μ) | RA: 88.02 ± 0.65 [1] mas/yr Dec.: −38.24 ± 0.51 [1] mas/yr |
| Parallax (π) | 22.68 ± 0.57 mas[1] |
| Distance | 144 ± 4 ly (44 ± 1 pc) |
| Absolute magnitude (MV) | −2.77 |
| Details | |
| Mass | 6–8 M☉ |
| Radius | ~10 R☉ |
| Luminosity | 3,311 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 ninth-brightest star in the nighttime sky. Of the top ten apparent brightest stars (excluding our Sun): Sirius, Canopus, Alpha Centauri, Arcturus, Vega, Capella, Rigel, Procyon, Achernar & Betelguese, Achernar is the hottest and bluest. It lies at the southern tip of the constellation.
Achernar is a bright, blue, B3-type star of six to eight solar masses lying approximately 144 light-years (44 parsecs) 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, roughly the latitude of Dallas, Texas. 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 although Antares is located in a constellation with many bright second magnitude stars whereas the stars surrounding Achernar and Fomalhaut are considerably fainter.
It is the least spherical star in the Milky Way studied to date. (See “Achernar the Flattest star” in ‘Sky &Telescope’ P. 20 ‘Newsnotes’, September 2003.) 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.
Fiction
References
External links
- Achernar at solstation.com
- Surface temperature and synthetic spectral energy distributions for rotationally deformed stars
