Delta1 Gruis
Delta1 Gruis, Latinized from δ1 Gruis, is a candidate binary star system in the constellation Grus. With a peak apparent visual magnitude of 4.0 it is bright enough to be seen with the naked eye at night. The distance to this system, as determined using an annual parallax shift of 10.54 mas as seen from the Earth, is around 309 light years. It is gradually moving away from the Sun with a radial velocity of +4.9 km/s.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Grus |
| Right ascension | 22h 29m 16.17481s |
| Declination | −43° 29′ 44.0245″ |
| Apparent magnitude (V) | 4.0 - 4.2 |
| Characteristics | |
| Spectral type | G6/8 III |
| U−B color index | +0.81 |
| B−V color index | +1.03 |
| Variable type | SR |
| Astrometry | |
| Radial velocity (Rv) | +4.9±0.8 km/s |
| Proper motion (μ) | RA: +25.72 mas/yr Dec.: −3.32 mas/yr |
| Parallax (π) | 10.54 ± 0.22 mas |
| Distance | 309 ± 6 ly (95 ± 2 pc) |
| Absolute magnitude (MV) | −1.1 |
| Details | |
| Mass | 4.0 M☉ |
| Radius | 24 R☉ |
| Luminosity | 305 L☉ |
| Surface gravity (log g) | 2.54±0.28 cgs |
| Temperature | 5,013±88 K |
| Metallicity [Fe/H] | −0.23±0.09 dex |
| Rotational velocity (v sin i) | 8.2 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
The brighter component of this system is an evolved, yellow-hued, G-type giant star with a stellar classification of G6/8 III. It is a semiregular variable that ranges between apparent magnitudes 3.99 and 4.2, located 325 light-years from Earth. Delta1 Gruis has around 3 times the mass and 24 times the diameter of the Sun. The fainter companion is a magnitude 12.8 star at an angular separation of 5.6 arc seconds, as of 2008.