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