Star caught swallowing a planet
Thu, 23 Aug 2012 1:08p.m.
By 3 News online staff
Astronomers for the first time have witnessed what they believe is a star swallowing one of its orbiting planets.
The star, known as BD+48 740 and located in the constellation of Pegasus, has a diameter 11 times larger than that of the Sun.
It is currently going through the 'red giant' phase of its life, where it balloons to many times its normal size, devouring planets that orbited close enough.
BD+48 740 also contains an "abnormally" high amount of lithium, one of the key indicators astronomers look for in events of this type.
"It is probable that the lithium production was triggered by a mass the size of a planet that spiralled into the star and heated it up while the star was digesting it," astronomer Alex Wolszczan told NBC News.
Lithium is a rare element, consumed by stars' normal fusion reactions. Consuming a planet however could result in the excess lithium detected.
The theory is backed up by the strange elliptical orbit of the star's only known other planet. Sixty percent larger than Jupiter, it comes closer to BD+48 740 than Mars does to our own Sun, but then swings out much further.
"Such orbits are uncommon in planetary systems around evolved stars and, in fact, the BD+48 740 planet's orbit is the most elliptical one detected so far," astronomer Andrez Miedzielski told the LA Times.
"The highly elongated orbit of the massive planet we discovered around this lithium-polluted red-giant star is exactly the kind of evidence that would point to the star's recent destruction of its now-missing planet," says astronomer Eva Villaver.
The astronomers said the find was highly improbable.
When the Sun reaches the end of its life in about 5 billion years, it may expand in size so greatly the Earth will be swallowed.
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