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Heavy-metal stars make lead clouds

Two helium-rich stars contain more of the element lead than astronomers have ever seen. The stars may represent an intermediate stage of stellar evolution in which heavy metals can become enriched and form cloud-like layers.

A team led by Naslim Neelamkodan and Simon Jeffery of Armagh Observatory near Belfast, UK, analysed light from nine subdwarf stars and discovered the two lead-rich stars about 250 parsecs and 300 parsecs from Earth, respectively. The researchers think that the stars could each contain as much as 100 billion tonnes of lead — up to 100 times the amount found in normal subdwarf stars.

Starlight exerts radiative pressure, a slight force that can nudge particles. This may drive the heavy metal to separate into a thin atmospheric layer, the team suggests.

Mon. Not. R. Astron. Soc. (2013)

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Heavy-metal stars make lead clouds. Nature 500, 124 (2013).

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