Theta Boötis
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| Observation data Epoch J2000 |
|
|---|---|
| Constellation (pronunciation) |
Boötes |
| Right ascension | 14h 25m 11.8s |
| Declination | +51° 51′ 03″ |
| Apparent magnitude (V) | 4.04 |
| Characteristics | |
| Spectral type | F7 V |
| U-B color index | 0.00 |
| B-V color index | 0.50 |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | -10.9 km/s |
| Proper motion (μ) | RA: -236.06 mas/yr Dec.: -399.07 mas/yr |
| Parallax (π) | 68.63 ± 0.56 mas |
| Distance | 47.5 ± 0.4 ly (14.6 ± 0.1 pc) |
| Absolute magnitude (MV) | 3.22 |
| Details | |
| Mass | 1.25-1.5 M☉ |
| Radius | ? R☉ |
| Luminosity | ? L☉ |
| Temperature | 6300 K |
| Metallicity | 85% |
| Rotation | 34 km/s. |
| Age | ~3 × 109 years |
| Other designations | |
Theta Boötis (θ Boo / θ Boötis) is a star in the constellation Boötes. It also has the traditional name Asellus Primus (Latin for "first donkey colt") and the Flamsteed designation 23 Boötis.
Theta Boötis has apparent magnitude +4.04 and belongs to the spectral class F7V. It is approximately 47 light years from Earth. From about 4300 BC until 3942 BC, it was the closest star to the celestial north pole visible to the naked eye, although it was still too far away and too dim to be regarded as a pole star.
There is a nearby 11th magnitude companion star about 70 arcseconds away. This is a class M2.5 dwarf that is separated by approximately 1,000 AUs. It is uncertain whether they are gravitationally-bound, but they do have a common motion through space and so the two stars likely share a common origin.
[edit] External links
- Theta Bootis by Professor Jim Kaler.
- ARICNS
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