Tau bootis
Double star Tau Bootis (τ Boo) |
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τ Boo is to the right below η Boo | ||||||||||||||||||||||||||||||||
Observation dates equinox : J2000.0 , epoch : J2000.0 |
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AladinLite | ||||||||||||||||||||||||||||||||
Constellation | Bear keeper | |||||||||||||||||||||||||||||||
Known exoplanets |
1 |
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Astrometry | ||||||||||||||||||||||||||||||||
Radial velocity | (−16.03 ± 0.15) km / s | |||||||||||||||||||||||||||||||
parallax | (63.86 ± 0.34) mas | |||||||||||||||||||||||||||||||
distance | (51.0 ± 0.3) ly (15.66 ± 0.08 pc ) |
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Proper movement : | ||||||||||||||||||||||||||||||||
Rec. Share: | (−467.91 ± 0.71) mas / a | |||||||||||||||||||||||||||||||
Dec. portion: | (64.70 ± 0.54) mas / a | |||||||||||||||||||||||||||||||
Individual data | ||||||||||||||||||||||||||||||||
Names | A; B. | |||||||||||||||||||||||||||||||
Observation data: | ||||||||||||||||||||||||||||||||
Right ascension
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A. | 13 h 47 m 15.737 s | ||||||||||||||||||||||||||||||
B. | 13 h 47 m 15.332 s | |||||||||||||||||||||||||||||||
declination
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A. | + 17 ° 27 ′ 24,790 ″ | ||||||||||||||||||||||||||||||
B. | + 17 ° 27 ′ 26,432 ″ | |||||||||||||||||||||||||||||||
Apparent brightness | A. | 4.54 mag | ||||||||||||||||||||||||||||||
B. | 11.1 mag | |||||||||||||||||||||||||||||||
Typing: | ||||||||||||||||||||||||||||||||
Spectral class | A. | F7 IV-V | ||||||||||||||||||||||||||||||
B. | M3 V | |||||||||||||||||||||||||||||||
B − V color index | A. | (+0.52) | ||||||||||||||||||||||||||||||
Physical Properties: | ||||||||||||||||||||||||||||||||
rel. Brightness (G-band) |
A. | (4.29 ± 0.01) mag | ||||||||||||||||||||||||||||||
B. | (9.47 ± 0.03) mag | |||||||||||||||||||||||||||||||
Absolute vis. Brightness M vis |
A. | +3.53 mag | ||||||||||||||||||||||||||||||
B. | +10.03 mag | |||||||||||||||||||||||||||||||
Dimensions | A. | (1.400 ± 0.070) M ☉ | ||||||||||||||||||||||||||||||
B. | (0,4) M ☉ | |||||||||||||||||||||||||||||||
radius | A. | (1.307 ± 0.065) R ☉ | ||||||||||||||||||||||||||||||
B. | 0.58 R ☉ | |||||||||||||||||||||||||||||||
Luminosity | A. | 3.1 L ☉ | ||||||||||||||||||||||||||||||
B. | 0.0084 L ☉ | |||||||||||||||||||||||||||||||
Effective temperature | A. | 6340 K | ||||||||||||||||||||||||||||||
B. | ||||||||||||||||||||||||||||||||
Metallicity [Fe / H] | A. | (0.28) | ||||||||||||||||||||||||||||||
B. | ||||||||||||||||||||||||||||||||
Age | (2.52) billion | |||||||||||||||||||||||||||||||
Other names and catalog entries |
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Tau Bootis (τ Boo / τ Bootis) is a binary star located 16 parsecs (50 light years ) away in the southwest of the Bear Keeper constellation . The system consists of the significantly brighter Tau Bootis A , which is a yellowish star of the spectral class F7 IV-V with an apparent brightness of 4.54 and can therefore also be clearly seen with the naked eye, as well as Tau Bootis B, which is invisible to the naked eye , a red dwarf with an apparent magnitude of 11.1, which orbits Tau Bootis A at a distance of 224 AU in 2,000 years on a strongly eccentric orbit (0.91) that is also inclined by 50.69 ° for the observer on earth is. An exoplanet around Tau Bootis A has been known since 1996 .
Components
Tau Bootis A
Tau Bootis A has a mass of 1.4 solar masses and, with an absolute brightness of 3.53, has a luminosity that is more than three times that of our sun. Its diameter is probably also slightly larger than that of the Sun, but Tau Bootis A is significantly younger with an age of less than 2 billion years. It contains twice as high a proportion of heavy elements as the sun and has a surface temperature of over 6,300 K. The total life span as a main sequence star is significantly shorter than that of the sun at 6 billion years.
A planetary companion was discovered in 1996 (see below). The rotation period of Tau Bootis corresponds to the orbital period of the planet (3.3 days), so that here there is a rare case of bound rotation in which the planet forces the rotation period on its star through corresponding tidal forces. The star has a magnetic field that interacts in complex ways with the nearby planet.
Tau Bootis B
Due to its low luminosity, Tau Bootis B can only be seen with powerful telescopes. The red dwarf has an absolute brightness of 10.03, a mass of only around a third of the solar mass and a radius that corresponds to around 60% of the solar radius; Tau Bootis B belongs to the spectral class M3 V.
Planetary system
→ Main article: Tau Bootis b
In 1996, a team of astronomers led by Geoffrey Marcy and R. Paul Butler discovered a planet around Tau Bootis A. The planet called Tau Bootis b and Tau Bootis Ab was one of the first ever discovered exoplanets. It orbits its central star in around 3.31 days at a distance of around 0.049 AU . Its mass is at least about 4.32 masses of Jupiter .
literature
- S. Horner et al .: 51 Pegasi and Tau Bootis: Planets or Pulsations? , Los Alamos Conference on Stellar Pulsation, June 1997
- A. Cameron et al .: Probable detection of starlight reflected from the giant exoplanet orbiting tau Bootis , Nature-Artikel, 1999
- C. Catala et al .: The magnetic field of the planet-hosting star tau Bootis , MNRAS, 2007
Web links
- Entry of the planet in the encyclopedia of extrasolar planets
- Entry at extrasolar.net
- Entry at solstation.com
Individual evidence
- ↑ a b tau Boo. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed April 20, 2019 .
- ↑ a b c d e f tau Boo A. In: SIMBAD. Center de Données astronomiques de Strasbourg, accessed April 20, 2019 .
- ↑ a b c d tau Boo B. In: SIMBAD. Center de Données astronomiques de Strasbourg, accessed April 20, 2019 .
- ↑ a b P. E. Kervella, F. Arenou, F. Mignard, F. Thévenin: Stellar and substellar companions of nearby stars from Gaia DR2. Binarity from proper motion anomaly . In: Astronomy & Astrophysics . 623, p. A72. arxiv : 1811.08902 . bibcode : 2019A & A ... 623A..72K . doi : 10.1051 / 0004-6361 / 201834371 .
- ↑ a b c Tau Bootis. Jim Kaler, accessed April 20, 2019 .
- ↑ a b tau Boo b. In: Extrasolar Planets Encyclopaedia . Retrieved April 20, 2019 .
- ↑ Walker, GAH et al .: MOST detects variability on tau Bootis possibly induced by its planetary companion . arxiv : 0802.2732 .
- ^ Butler, R. Paul et al .: Three New "51 Pegasi-Type" Planets . bibcode : 1997ApJ ... 474L.115B .
- ↑ Borsa, F .; Scandariato, G .; Rainer, M. et al .: The GAPS Program with HARPS-N at TNG. VII. Putting exoplanets in the stellar context: magnetic activity and Asteroseismology of τ Bootis A . arxiv : 1504.00491 .