Epsilon Gruis
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Grus |
| Right ascension | 22h 48m 33.29833s |
| Declination | −51° 19′ 00.7001″ |
| Apparent magnitude (V) | 3.466 |
| Characteristics | |
| Spectral type | A2 IVn |
| B−V color index | 0.09 |
| Astrometry | |
| Radial velocity (Rv) | −0.4±2.1 km/s |
| Proper motion (μ) | RA: +108.43 mas/yr Dec.: −64.83 mas/yr |
| Parallax (π) | 25.30±0.48 mas |
| Distance | 129 ± 2 ly (39.5 ± 0.7 pc) |
| Absolute magnitude (MV) | +0.52 |
| Details | |
| Mass | 1.85 M☉ |
| Surface gravity (log g) | 3.47±0.14 cgs |
| Temperature | 8,685±295 K |
| Metallicity [Fe/H] | −0.16 dex |
| Rotational velocity (v sin i) | 235.1±11.8 km/s |
| Age | 249 Myr |
| Other designations | |
| ε Gru, CD−51°13389, FK5 860, GJ 9796, HD 215789, HIP 112623, HR 8675, SAO 247593 | |
| Database references | |
| SIMBAD | data |
ε Gruis, Latinised as Epsilon Gruis, is a blue-white hued star in the southern constellation of Grus. It is visible to the naked eye, having an apparent visual magnitude of 3.5. Based upon an annual parallax shift of 25.30 mas as measured from Earth, it is located around 129 light years from the Sun. The system may be moving closer to the Sun with a radial velocity of about −0.4 km/s.
This is an A-type subgiant of spectral type A2IVn, a star that has used up its core hydrogen and has begun to expand off the main sequence. At the estimated age of 249 million years, it is spinning rapidly with a projected rotational velocity of 235 km/s. This is giving the star an oblate shape with an equatorial bulge that is an estimated 18% larger than the polar radius. The star displays an infrared excess, suggesting the presence of a circumstellar disk of orbiting dust.
Epsilon Gruis is suspected of having a moderately active close companion, which is most likely the source of the weak X-ray emission from these coordinates with a luminosity of 1.3×1028 erg s−1.