Relationships are all about give and take -- including relationships between stars. But in the case of stars, it's usually a one-way street -- one star does all the giving, while the other does all the taking.
An example is a system known as RS Ophiuchi. It's in the large constellation Ophiuchus, the serpent bearer, which climbs across the south on June nights.
RS Ophiuchi consists of two stars. One of them is a red giant -- a star that's puffed up like a big balloon as it nears the end of its life. The other is a white dwarf. It's even later in life -- it's lost its outer layers of gas, leaving only its hot, dense core.
The red giant is blowing a lot of its gas into space, too. That surrounds the two stars in a dense nebula. Some of the nebula's gas piles up on the surface of the white dwarf, while more forms a thin, hot disk around it. The white dwarf also pulls gas off the surface of the red giant, adding to that from the nebula.
As the gas piles up, it gets extremely hot. And every two or three decades, it explodes, making the star shine about 50,000 times brighter than the Sun. The explosion destroys the disk of gas around the white dwarf, leaving it bare.
Within a few months, though, the process starts all over again. Since 1898, RS Ophiuchi has erupted five times -- most recently in 2006. Today, the white dwarf is once again taking what the red giant gives -- more gas that could one day trigger another powerful explosion.
Script by Damond Benningfield, Copyright 2009
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