Omicron Aquarii
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 22h 03m 18.844s |
| Declination | −02° 09′ 19.31″ |
| Apparent magnitude (V) | +4.71 |
| Characteristics | |
| Spectral type | B7 IVe |
| U−B color index | −0.39 |
| B−V color index | −0.11 |
| Variable type | γ Cas |
| Astrometry | |
| Radial velocity (Rv) | +11.0 km/s |
| Proper motion (μ) | RA: +24.593 mas/yr Dec.: −11.720 mas/yr |
| Parallax (π) | 6.9984±0.1424 mas |
| Distance | 466 ± 9 ly (143 ± 3 pc) |
| Absolute magnitude (MV) | −0.89 |
| Details | |
| Mass | 4.2 M☉ |
| Radius | 4.0±0.3 R☉ |
| Luminosity | 340 L☉ |
| Surface gravity (log g) | 3.13 cgs |
| Temperature | 11,145±498 K |
| Metallicity [Fe/H] | −0.16 dex |
| Rotational velocity (v sin i) | 211±26 km/s |
| Other designations | |
| ο Aqr, 31 Aquarii, BD−02 5681, FK5 3765, HD 209409, HIP 108874, HR 8402, SAO 145837 | |
| Database references | |
| SIMBAD | data |
Omicron Aquarii is a variable star in the equatorial constellation of Aquarius. Its name is a Bayer designation that is Latinized from ο Aquarii, and abbreviated Omicron Aqr or ο Aqr. Visible to the naked eye, it has an apparent visual magnitude of +4.71. Parallax measurements put it at a distance of roughly 466 light-years (143 parsecs) from Earth. It is drifting further away with a radial velocity of +11 km/s. The star is a candidate member of the Pisces-Eridanus stellar stream of co-moving stars.
It has the traditional star name Kae Uh, from the Chinese 蓋屋 (Mandarin pronunciation Gài Wū). In Chinese astronomy, 蓋屋 is the rooftop, an asterism consisting of ο Aquarii and 32 Aquarii. Consequently, the Chinese name for ο Aquarii itself is 蓋屋一 (Gài Wū yī, English: the First Star of Roofing.)