Tau Boötis
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| Observation data Equinox J2000 |
|
|---|---|
| Constellation | Boötes |
| Right ascension | 13h 47m 15.7s |
| Declination | +17° 27′ 25″ |
| Apparent magnitude (V) | 4.50/11.00 |
| Characteristics | |
| Spectral type | F6 IV/M2 V |
| U-B color index | 0.04 |
| B-V color index | 0.48 |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | -15.6 km/s |
| Proper motion (μ) | RA: -480.34 mas/yr Dec.: 54.18 mas/yr |
| Parallax (π) | 64.12 ± 0.70 mas |
| Distance | 50.84 ly (15.60 pc) |
| Absolute magnitude (MV) | 3.53/10.03 |
| Details | |
| Mass | 1.3/0.4 M☉ |
| Radius | 1.4 R☉ |
| Luminosity | 3.4 L☉ |
| Temperature | 6340 K |
| Metallicity | 210% |
| Rotation | ? |
| Age | 1.3-2.0 × 109 years |
| Other designations | |
Tau Boötis (τ Boo / τ Boötis) is a 4th magnitude star system in the constellation of Boötes. The system is a binary. The primary component is a yellow-white dwarf (spectral type F7 V) and secondary is a dim red dwarf (spectral type M2 V).
The system is relatively nearby, distance being about 51 light years. The primary star should be easily visible to the unaided eye under dark skies.
The primary star, Tau Boötis A is a yellow-white dwarf. It is 20% more massive than our Sun and thus is somewhat brighter and hotter. It has a radius 1.9 times solar, and is probably about 1300 million years old. Since it is more massive than the Sun, its lifespan is shorter being less than 6000 million years.
It is also listed as a suspected variable star. However, the star is not variable.
Tau Boötis B is a dim red dwarf orbiting the primary star at a distance of 240 AU. One orbit around the primary would take thousands of years to complete.
[edit] Planetary system
In 1997 a planet, designated as Tau Boötis Ab was discovered orbiting the primary star. Tau Boötis is the only known example of a star tidally locked by a planet.[citation needed] There are also some indications of another, more distant planet orbiting the star.
| Planet | Mass (MJ) |
Semimajor axis (AU) |
Orbital period (days) |
Eccentricity |
|---|---|---|---|---|
| b | >7-8 | 0.05 | 3.312 | 0.01 |
[edit] References
- Butler et al. (1997). "Three New 51 Pegasi Type Planets". The Astrophysical Journal 474: L115-L118.
[edit] External links
- SIMBAD component A entry component B entry
- The Extrasolar Planets Encyclopaedia entry
- Extrasolar Visions entry
- Article about Tau Boötis tidally locked by planet
- Tau Bootis by Professor Jim Kaler.
- Tau Boötis 2 at SolStation.com.
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