Epsilon Tucanae
Star in the constellation Tucana
From Wikipedia, the free encyclopedia
Epsilon Tucanae (ε Tuc, ε Tucanae) is a solitary[10] star in the southern constellation of Tucana. With an apparent visual magnitude of +4.50,[2] it is faintly visible to the naked eye. Based upon an annual parallax shift of 8.74 mas as seen from Earth, it is located around 373 light years from the Sun.
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Tucana |
| Right ascension | 23h 59m 54.97761s[1] |
| Declination | −65° 34′ 37.6804″[1] |
| Apparent magnitude (V) | +4.50[2] |
| Characteristics | |
| Evolutionary stage | main sequence[3] |
| Spectral type | B8 V[4] or B9 IV[5] |
| U−B color index | −0.28[2] |
| B−V color index | −0.08[2] |
| Astrometry | |
| Radial velocity (Rv) | +8.8±2.8[6] km/s |
| Proper motion (μ) | RA: +47.93[1] mas/yr Dec.: −22.95[1] mas/yr |
| Parallax (π) | 8.74±0.18 mas[1] |
| Distance | 373 ± 8 ly (114 ± 2 pc) |
| Absolute magnitude (MV) | −0.80[7] |
| Details | |
| Mass | 4.00±0.20[4] M☉ |
| Luminosity | 389[4] L☉ |
| Surface gravity (log g) | 3.9±0.1[4] cgs |
| Temperature | 13,000±500[4] K |
| Rotation | 0.79318(8)[8] d |
| Rotational velocity (v sin i) | 300±20[4] km/s |
| Age | 123[4] Myr |
| Other designations | |
| ε Tuc, CPD−66°3819, FK5 903, HD 224686, HIP 118322, HR 9076, SAO 255619[9] | |
| Database references | |
| SIMBAD | data |
Levenhagen and Leister (2008) classified this star as B8 V,[4] indicating a blue-white hued B-type main sequence star. However, Hiltner, Garrison, and Schild (1969) listed it with a classification of B9 IV,[5] suggesting it may be a more evolved subgiant star. It is a rapidly rotating Be star that is an estimated 78% of the way through its main sequence lifetime.[3] The projected rotational velocity is 300 km/s,[4] which is giving it an oblate shape with an equatorial bulge that is an estimated 36% larger than the polar radius.[11] It has a weak magnetic field with a strength of 74±24 G.[12]
It is the last star in the Hipparcos catalogue, HIP 118322, from the Hipparcos (1989–1993) astrometry satellite.