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Diamond Grains Waft Among Stars

6 May 2002 (All day)
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Cosmic carats. The nanodiamonds (white powder in vial) found in meteorites also drift in the dust among stars.

Our galaxy is a jeweler's delight, according to new research. A subtle pattern imprinted upon ultraviolet light from nearby stars suggests that diamond dust drifts in the vast spaces among stars. However, don't invest in a deep-space mining venture just yet: The diamonds measure just a few nanometers across.

The first evidence of diamonds in outer space turned up 15 years ago, within meteorites. Ancient supernovas forged the grains, and when our solar system formed about 4.6 billion years ago, asteroids incorporated the dust. If supernovas spew out diamonds, astronomers reasoned, they must be a common part of our galaxy's dust--accounting for 5% of the carbon in space, according to one calculation. Previous studies suggested that the grains may concentrate in the cocoons of dust enshrouding young stars, because the meteorite diamonds absorb infrared light in a pattern similar to the light absorbed by grains around young stars.

Now, a separate spectral pattern in ultraviolet light points to widespread diamond dust throughout space, not just around newborn stars. A team led by astronomer Geoffrey Clayton of Louisiana State University in Baton Rouge used the Hubble Space Telescope and archival data from the former International Ultraviolet Explorer satellite to examine the light from several stars behind large clouds of dust. A faint but distinct pattern, known to arise only from diamond grains, appeared in every direction the team looked, they report in the 10 June issue of Astrophysical Journal Letters. Diamond grains are nearly indestructible and should accumulate in the galaxy over time, Clayton says. Based on the new data, his team estimates that the Milky Way contains about 1041 grams of diamonds--nearly a million trillion trillion trillion carats.

The new research has an "intriguing result," says astrophysicist Walter Duley of the University of Waterloo in Ontario, Canada. "But I'm a little skeptical of the firmness of the identification," he notes, because the team hasn't yet ruled out whether other substances, especially polycyclic aromatic hydrocarbons, could produce a similar ultraviolet pattern. Clayton and his colleagues plan to explore those signatures in a follow-up study.

Related sites
Abstract of the report
Stardust, a NASA mission collecting interstellar and cometary dust
Background on the interstellar medium

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