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ADS 9731
ADS 9731 is a star system that consists of six stars. Four of the stars are visually separate in the sky, forming a visual star system, which was resolved using adaptive optics in 1995.〔 Two of these stars were themselves found to be spectroscopic binaries in 1998, resulting in a total of six known stars in the system.〔 It is one of very few multiple star systems known to have at least six members.〔 The components are organised thus: Aa and Ab are yellow-white main sequence stars of spectral types F4V and F5V and 1.35 and 1.32 solar masses respectively, which orbit each other every 3.27 days. This pair is in a 450-year orbit with star B, a star of spectral type G4V that has around the same mass as the Sun. Star C is a yellow white star of spectral type F3V around 1.41 times as massive as the sun, which has just started brightening and moving off the main sequence. It is in a 1000-year orbit with a pair of stars, Da and Db, a yellow-white main sequence star of spectral type F7V and a red dwarf of spectral type M3V. Da and Db take 14.28-days to orbit each other. Finally the system of stars C and Dab, and the system of stars Aab and B, take over 20,000 years to orbit each other.〔
The combined light from the whole system results in an integrated V magnitude of 6.9. The parallax measured by the Hipparcos satellite indicates that the system is relatively nearby at around from the Sun.〔 However, this distance is highly uncertain because the multiple stars in the system prevented Hipparcos from accurately measuring the parallax; the system may instead be at a distance of about .〔
The star system has been considered as a possible target for direct imaging searches for exoplanets,〔 but no planets have yet been detected in the system.
==References==
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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