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The Question
(Submitted February 02, 1998)
I have a couple of
questions for you on binary stars. I would just like
to know how the stars got their name "Binary," which
scientist discovered them, and why people find them so
interesting.
The Answer
'Binary' just means having two parts, and you
will find it used in many places (whenever there are two of something) and
not just in connection with stars. The English astronomer William Herschel
coined the term binary star, after an investigation in the 1790s of stars
that appear close together in the sky showed that many were indeed pairs of
stars traveling together. Binary stars are very important in astronomy,
because a lot of things which are hard to discover when stars are on their
own can be easily measured when two are together. When two things are close
together, the effect each other in many ways, and we can learn a lot from
those effects. For example, two stars close together exert a gravitational
pull on each other changing the way they move. By measuring their movements
very carefully we can often figure out how much material is in each star -
how heavy it is.
Paul Butterworth
for the Ask an Astrophysicist team
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