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Tau Boötis

A double of a yellow star and a red dwarf. The bigger of the two is orbited by a planet with 8 times the mass of Jupiter. This got the name Millenium Planet, because it was the first one to be discovered in 2000. It is very close to its star (0.046 AU) and orbits it every 3.3124 days.

Planet as star are tidally locked. This means all the time they show each other the same side. With near planets this is inevitable, but from a star this hasn't been expected.

Constellation: Boötes
Age: 1.3 - 2 billion years
Distance: 50.9 light-years
Orbit period of Tau Boötis A and B: 2000 years
Radial velocity: -16.1 km/sec

Tau Boötis A

Spectral class: F7
Visual magnitude: 4.50
Luminosity: 3.36 * Sun
Mass: 1.3 * Sun
Diameter: 1.68 * Sun

Tau Boötis B

Spectral class: M2
Visual magnitude: 11.00
Luminosity: 0.0084 * Sun
Mass: 0.2 * Sun
Diameter: 0.58 * Sun

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