Lithium shows scientists where to find far-off planets

15 November 2009


A European team of scientists may have discovered a shortcut to finding distant planets orbiting far-off stars - you look for lithium, or rather a lack of it...

Lithium is the third lightest element in the Universe and small amounts were produced, alongside hydrogen and helium, by the Big Bang. Consequently it turns up together with these two other elements in stars and ought to be present in roughly the same amounts everywhere.

But a long-standing mystery scientists haven't been able to explain is why some stars appear to have plenty of the stuff, the presence of which is apparent within the spectrum of light given off by a star, whilst others - our own Sun included - contain less than 1% of this amount.

To get to the bottom of the problem, Garik Israelian and his colleagues, writing in Nature, surveyed more than 500 similar stars, including 70 known to have planets orbiting them.

When the data from these stars were compared, and factors such as age were taken into account, a surprising trend emerged. Stars like our own Sun, with planets, lacked lithium, whilst their more lonely counterparts were more likely to be lithium replete.

The researchers think that the presence of planets somehow stirs up the substance of the star, pulling the lithium from the star's surface to the much hotter interior where it is consumed.

The team say it's now up to the theoriticians to figure out exactly how this happens, but the key point is that looking for a lack of lithium in the spectral signature coming from a star could provide space scientists with a shortcut way to find new planets much more quickly.


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