Free Astronomy Magazine January-February 2020

EXOPLANETS 25 a en JANUARY-FEBRUARY 2020 N early 400 light-years from Earth, in the constellation Aries, there is a very closely spaced star system, a so-called “spectroscopic binary,” which has attracted the attention of astronomers for over a decade. That system is known as BD +20 307 and is composed of two solar-type stars orbiting around their common center-of- mass in 3.4 days. They are so close together that they could almost be considered a sin- gle star for the purposes of the existence and orbital stability of any planets.