Theta Boötis
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Boötes |
| Right ascension | 14h 25m 11.797s |
| Declination | +51° 51′ 02.68″ |
| Apparent magnitude (V) | 4.05 + 13.23 |
| Characteristics | |
| Spectral type | F7 V + M2.5V |
| U−B color index | −0.02 |
| B−V color index | +0.50 |
| Astrometry | |
| Radial velocity (Rv) | −10.627±0.0065 km/s |
| Proper motion (μ) | RA: −235.97 mas/yr Dec.: −399.696 mas/yr |
| Parallax (π) | 69.0686±0.1579 mas |
| Distance | 47.2 ± 0.1 ly (14.48 ± 0.03 pc) |
| Absolute magnitude (MV) | 3.25 |
| Details | |
| A | |
| Mass | 1.232±0.012 M☉ |
| Radius | 1.726±0.012 R☉ |
| Luminosity | 4.205±0.020 L☉ |
| Surface gravity (log g) | 4.06±0.02 cgs |
| Temperature | 6,292±20 K |
| Metallicity [Fe/H] | 0.03 dex |
| Rotational velocity (v sin i) | 29.2 km/s |
| Age | 3.1 Gyr 3.83 Gyr |
| B | |
| Mass | 0.4–0.48 M☉ |
| Radius | 0.4013±0.012 R☉ |
| Luminosity | 0.022 L☉ |
| Surface gravity (log g) | 4.91 cgs |
| Temperature | 3,521 K |
| Metallicity [Fe/H] | −0.07 dex |
| Other designations | |
| Asellus Primus, θ Boo, 23 Boötis, NSV 6669, BD+52°1804, FK5 531, GC 19467, GJ 549, HD 126660, HIP 70497, HR 5404, SAO 29137, PPM 34508, WDS J14252+5151A, LTT 14245 | |
| Database references | |
| SIMBAD | data |
| ARICNS | data |
Theta Boötis is a star in the northern constellation of Boötes the herdsman, forming a corner of the upraised left hand of this asterism. Its name is a Bayer designation that is Latinized from θ Boötis, and abbreviated Theta Boo or θ Boo. This star has the traditional name Asellus Primus, pronounced /əˈsɛləs ˈpraɪməs/, which is Latin for "first donkey colt". Faintly visible to the naked eye, this star has a yellow-white hue with an apparent visual magnitude of 4.05. It is located at a distance of 47.2 light-years (14.5 pc) from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −10.6 km/s. It has a relatively high proper motion, traversing the celestial sphere at the rate of 0.464 arc seconds per annum.