Heavy metal stars shine under leaden skies far away in the universe

Two stars just discovered by astronomers at Armagh Observatory are so hot that their atmosphere contains a lead layer more than 100km thick.

Lead is one of the heaviest of the naturally occurring elements and the stars are part of a new category of stars called heavy metal sub-dwarfs.

Officially named HE2359-2844 and HE1256-2738, the stars only have a fifth of the radius of the sun but are many hundreds of times brighter.

HE2359-2844, which is 800 light years away from Earth, in the constellation of Sculptor, has been nicknamed Metallica. Of the two it has the higher concentration of lead.

HE1256-2738, which is 1,000 light years away, in the constellation of Hydra, has been dubbed Dark Angel, after a trash metal band from Los Angeles.
"We thought it was appropriate to name them after rock bands," said lead researcher Simon Jeffrey.

In its solid or molten form, lead is synonymous with greyness but at 38,000 degrees it forms a bright blue gas.

The light signature, or spectra, of this gas was picked up by the European Southern Observatory's Very Large Telescope in Chile.

HE1256-2738 also contains large quantities of zirconium, the element used in fake diamonds, and found in yttrium, a rare-earth mineral.

Metal-rich hot sub-dwarf stars are extremely rare. In our Milky Way galaxy there are some 200 billion stars, but only 2,000-3,000 of them fit the category.

“This is like finding a needle in a haystack without even looking for a needle,” said Prof Jeffrey.