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Disappearing space dust belt baffles boffins

Did star spit out planet after inhaling galactic powder?

Boffins were bewildered when a star's dust belt mysteriously disappeared, but they now think that the vanishing fragments could have used up in some superfast planet formation.

Artist's impression of dusty TYC 8241 2652 1

TYC in its formerly dusty state. Credit: Gemini Observatory/AURA artwork by Lynette Cook

Researchers had spotted the cloud of dust circling the young star in the Scorpius-Centaurus stellar nursery in data gathered by the Infrared Astronomical Satellite while it was was surveying the sky back in 1983.

It would usually take hundreds of thousands, if not millions of years for the amount of dust orbiting the lengthily named TYC 8241 2652 1 (we're going to call it TYC for short) to dissipate, so when the boffins saw the star again in 2008 using the mid-infrared imager at the Gemini South Observatory in Chile, they weren't surprised to see things were just the same as 25 years ago.

But when TYC was viewed from the same telescope in 2009, something weird had happened: the infrared emission, by which the scientists could infer the presence of the dust, had dropped by two-thirds. By 2010, when NASA's Wide-field Infrared Survey Explorer (WISE) glimpsed the celestial body, the dust was almost all gone.

"It's like the classic magician's trick: Now you see it, now you don't," lead author Carl Melis, a postdoc at UC San Diego, said. "Only in this case we're talking about enough dust to fill an inner solar system, and it really is gone."

After checking again with the Japanese AKARI telescope and the ESA's Photodetector Array Camera and Spectrometer at the Herschel Space Observatory, just to be on the safe side, the boffins set about scratching their heads to figure out where the dust might have vanished to.

Scientists have long hypothesised that planetary formation takes place after hundreds of thousands of years of minute particles clumping together through weak electrostatic interactions and eventually gravitational forces.

But this observation could mean that planets can actually be whipped up in no time if the conditions are right.

"If what we observed is related to runaway growth, then our finding suggests that planet formation is very fast and very efficient," said Inseok Song, the study's co-author and assistant professor of physics and astronomy at the University of Georgia.

"The implication is that if the conditions are right around a star, planet formation can be nearly instantaneous from an astronomical perspective."

Unfortunately, the star is 450 light years away so the boffins can't see any planet that might have formed around TYC... so this leaves the disappearance of the dust open to other theories interpretations as well.

The dust might have been sucked back into the star, effectively eliminating planet-building material, which would mean the formation of new worlds is less likely than previously thought.

Or the star could have spat the dust out, expelling it from orbit with the constant stream of photons emanating from the sun, pushing the teeny-tiny dust particles into each other and away.

"Many astronomers may feel uncomfortable with the suggested explanations for the disappearance of the dust because each of them has non-traditional implications," Song said, "but my hope that this line of research can bring us closer to a true understanding of how planets form."

The study has been published in Nature. ®

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