Binary Star

Two stars in orbit around each other, held together by their mutual gravity. It's like two balls (of burning gasses) connected by a stick (gravity) that's spinning in the middle, except it's not at the middle, it's at the centre of gravity. Somewhere around 5-10% of the stars be can see are binary stars. There are several classes of binary star systems:

• Visual binary stars can be seen and distinguished as two stars through a telescope.
• Spectroscopic binary stars are binary stars so close that they appear to be one star through a telescope. We can determine them to be binary stars through wavelength fluctuations from the doppler effect. These stars are subclassed as double-lined spectroscopic binary stars and single-lined spectroscopic binary stars.
• Eclipsing binary stars are alligned so one eclipses the other from time to time.

Binary stars are extremely useful because we can find their distance easily using spectroscopic parallax, or other methods. Additionally some binary systems appear have black holes in place of the stars. Half of the stars in our galaxy are in binary systems.

Also called "Double Stars".

Sources:
The New York Library Science Desk Reference
A few websites from long before we kept reference listings. (Good ol' E1)
http://astrosun.tn.cornell.edu/courses/astro201/binstar.htm
Astronomy with Dr. Martin Bier (great teacher) and the textbook Horizons by Michael A. Seeds

• New Hip Hop (Independent, The Terrorist Records, 1998, four song EP)
• Waterworld (Independent, The Terrorist Records, 1999, Full-length LP)
• Master Of The Universe (Subterraneous Records, 2000, remixed and re-released version of the Waterworld LP)