Tau Bootis

Artist impression. Credit: PPARC

A nearby binary star system in the constellation Boötes. It consists of an F star primary, Tau Bootis A, and a red dwarf companion, Tau Bootis B. The red dwarf moves around the primary in an extraordinarily elongated path (eccentricity = 0.91), taking about 2,000 years to complete each circuit at an average distance of 245 astronomical units (37 billion km, or 23 billion miles). A massive planet has been found in orbit around the primary at less than one eighth the distance of Mercury from the Sun, making it one of the most extreme examples yet found of an epistellar jovian.

Host star : Tau Bootis A
Apparent magnitude	4.50
Spectral type	IV
Distance	50.84 light-years (15.60 pc)
Temperature	6,340 K (6,070°C)
Luminosity (Sun = 1)	3.4
Mass (Sun = 1)	1.3
Position	R.A. 13h 47m 15.7s, Dec. +17° 27' 25"
Other designations	4 Boötis, GJ 527, HR 5185, BD +18°2782, HD 120136, SAO 100706, HIP 67275, GC 18637

Planet
Mass (Jupiter = 1)	4.13
Semimajor axis	0.05 AU (7.5 million km, 4.7 million miles)
Orbital period	3.31 days
Eccentricity	0.015
Year of discovery	1996
Discoverers	Butler et al, Berkeley Planet Search
Method of discovery	radial velocity

Related categories

• NOTABLE STARS
• EXTRASOLAR PLANETS AND SUBSTELLAR OBJECTS

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