Xi Boötis
Xi Boötis is a binary star system in the northern constellation of Boötes. Its name is a Bayer designation that is Latinised from ξ Boötis, and abbreviated Xi Boo or ξ Boo. This is the nearest visible star in the constellation Boötes. The brighter, primary component of the pair has a typical apparent visual magnitude of 4.70, making it visible to the naked eye. Based on parallax measurements, it is located at a distance of from Earth. The pair are drifting further from the Sun with a radial velocity of +2 km/s.
Properties
The primary star in this system is a G-type main-sequence star with a stellar classification of G8 Ve, where the 'e' notation indicates emission lines in the spectrum. It is a BY Draconis variable with an apparent magnitude that varies from +4.52 to +4.67 with a period just over 10 days long. The magnetic activity in the star's chromosphere varies with time, but no activity cycle has been found. It has 88% of the mass and 82% of the radius of the Sun, but shines with just 56% the Sun's luminosity.The secondary component is a smaller K-type main-sequence star with a class of K4 Ve. It has 66% of the Sun's mass and 61% of the Sun's radius. The star is radiating just 6.1% of the luminosity of the Sun from its photosphere at an effective temperature of 4,350 K. This gives it an apparent visual magnitude of 6.8, which by itself would be a challenge to view with the naked eye. As of 2019, it is located at an angular separation of from the primary, along a position angle of 298°.
The pair follow a wide, highly elliptical orbit around their common barycenter, completing an orbit every 152.5 years. Radial velocity measurements taken of the primary as part of an extrasolar planet search show a linear trend in the velocities that is likely due to the secondary star. The pair can be resolved using a small telescope. The binary system contains two of the closest young solar-type stars to the Sun, with a system age of about 200 million years old.
The primary star, component A, has been identified as a candidate for possessing a Kuiper-like belt, based on infrared observations. The estimated minimum mass of this dust disk is 2.4 times the mass of the Earth's Moon.
A necessary condition for the existence of a planet in this system are stable zones where the object can remain in orbit for long intervals. For hypothetical planets in a circular orbit around the individual members of this star system, this maximum orbital radius is computed to be for the primary and 3.5 AU for the secondary. A planet orbiting outside of both stars would need to be at least 108 AU distant.