Asteroid dust in and around dead stars hints at Earth-like planets

January 7th, 2009 - 1:35 pm ICT by ANI  

London, Jan 7 (ANI): Scientists have observed asteroid dust in and around a handful of dead stars, that is made up of similar materials as the Earth, which suggests Earth-like planets may be common in the Universe.

According to a report in New Scientist, six white dwarfs, the burned-out embers of Sun-like stars, showed heavy elements, or metals, in their atmospheres.

That is unusual because white dwarfs contain about as much mass as the Sun squeezed into bodies the size of the Earth, giving them surface gravities 10,000 times stronger than the Suns.

That should cause heavy elements to sink towards their centres - and out of sight.

In addition, the six stars also shine more brightly than expected in infrared light, which suggests the stars are surrounded by dust, which glows at infrared wavelengths.

The dusty debris is thought to be the remains of asteroids that once orbited the white dwarfs, but were gravitationally torn apart when they wandered too close to the stars.

Michael Jura of the University of California, Los Angeles, and colleagues measured the infrared light from these stars using NASAs Spitzer Space Telescope.

The team found the dust contains a glassy silicate material similar to olivine, which is common on Earth and has also been seen on the Moon and Mars.

The dust also seems to have no carbon, consistent with Earths composition, which has little carbon compared to the Sun.

Two previously studied white dwarfs have dust of a similar composition, bringing the tally of such stellar gluttons up to eight.

What was once kind of a freak is now a systematic pattern, Jura said.

Since asteroids form in the same way as planets, by bulking up through collisions between smaller rocky objects, they have a similar composition to their larger brethren.

That suggests terrestrial planets might have once existed in these systems. This strengthens suspicions that Earth-like planets are common, Jura said. (ANI)

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