Planets with Two or More Suns

Extrasolar planets in binary star systems were, at first, unexpected, since it was thought that the presence of a second or even third star would disrupt the formation of a planet in the first place. But then why have 30 such exoplanets been found in double and triple star groupings? Moreover, some of the planets detected reside in systems where the companion stars are not far away but actually rather close in -- tens of astronomical units (one AU equals the Earth-Sun distance) or less.

At this week's meeting of the American Astronomical Society (AAS) in Washington, D.C., Alan Boss argued that the presence of a second star, far from disrupting the formation of planets around the first star from diffuse matter, can actually enhance the enterprise. Boss, an astronomer at the Carnegie Institution of Washington, said that the cross-gravitational forces operating in a multiple-star system can in some cases, through the process of shock heating, trigger a faster development of dense spiral arms in which gas and dust clumping can lead to planets.

Since an estimated two-thirds of all stars in the Milky Way reside in complex groupings, Boss asserted that a theory allowing for matter agglomeration in such places would greatly increase the number of suitable targets for exoplanet hunters.

Images on Alan Boss's Web page