Widely Spaced Two Star Systems Dangerous for Alien Planets

Alien planets that are born in widely separated two-star systems face a serious danger of being kicked out into interstellar space, suggests a new study.

The study found that exoplanets that circle a star with a distant stellar companion, or worlds that are part of a "wide binary" system, are more susceptible to violent and dramatic orbital disruption, including outright ejection. This tends to only happen in sprawling planetary systems with at least one distantly orbiting world, and more compact systems are relatively immune.

Researchers say that this finding should help astronomers better understand the structure and evolution of alien solar systems across the galaxy.

Lead author Nathan Kalb, of Northwestern University and the University of Toronto, said:

"The fact that planets observed within wide binaries tend to have more eccentric (or 'excited') orbits than those around isolated stars tells us that wide binaries do often disrupt planetary systems. Thus, we believe most planetary systems are extended, with outer planets orbiting at tens of AU from their host stars."

One AU, or astronomical unit, equals the distance from Earth to the sun, or about 93 million miles.

The study was published on Sunday in the journal Nature. Kalb will be presenting the study today at the 221st meeting of the American Astronomical Society in Long Beach, Calif.