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The Question

(Submitted April 02, 1998)

What percentage of the stars are binary systems?

The Answer

Somebody once said that "2 out of every 3 stars are in a binary". Seriously, the fraction is very high, but it's difficult to be precise, because it's difficult to prove that a certain star is definitely single. Of the stars nearest to the Sun, about half are known to be in multiple systems.

Koji Mukai
for Ask an Astrophysicist

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