Most Milky Way stars are single

Common wisdom among astronomers holds that most star systems in the Milky Way are multiple, consisting of two or more stars in orbit around each other. Common wisdom is wrong.

A new study by Charles Lada of the Harvard-Smithsonian Center for Astrophysics (CfA) demonstrates that most star systems are made up of single stars. Since planets probably are easier to form around single stars, planets also may be more common than previously suspected.

Astronomers have long known that massive, bright stars, including stars like the sun, are most often found to be in multiple star systems. This fact led to the notion that most stars in the universe are multiples. However, more recent studies targeted at low-mass stars have found that these fainter objects rarely occur in multiple systems. Astronomers have known for some time that such low-mass stars, also known as red dwarfs or M stars, are considerably more abundant in space than high- mass stars.

By combining these two facts, Lada came to the realization that most star systems in the galaxy are composed of solitary red dwarfs.

“By assembling these pieces of the puzzle, the picture that emerged was the complete opposite of what most astronomers have believed,” said Lada.

This research has been submitted to The Astrophysical Journal Letters for publication and is available online at http://arxiv.org/ abs/astro-ph/0601375