(Submitted March 30, 2001)
How are binary star systems formed?
This is a very good question and, perhaps much to your
surprise, this can be a hot topic for a debate among
In essence, a binary-star system emerges out of a cloud
of gaseous material collapsing and forming more than a
single star at the same time in a small proximity. This
type of a collapsing event does not necessarily form only
two stars -- it can form more than two, but it all depends
on their unique environment in which stars form.
Also it is most unlikely for a single star to capture
another star in a typical stellar space. When two stars
encounter, they tend to swing by each other and almost
never captures one to another by their own gravitational
field. We are not going to explain why it is so, but you
will need more than two stars (in fact, many stars) to
do just that. Some cases of binary-capture may have been
seen in a place like globular clusters where a million of
stars are found in a very tiny volume of space.
Hope this helps,
Koji & Bish
for "Ask an Astrophysicist"