NASA spots X-ray super outbursts

Super X-ray flares torching our solar system have been spotted by NASA's Chandra Observatory in the Orion Nebula, which likely affected the planet-forming disk around the early sun, and may have enhanced the survival chances of Earth-like planets, scientists said Tuesday.

A team of scientists have obtained the deepest X-ray observations ever taken of any star cluster after focusing on the Orion Nebula almost continuously for 13 days using Chandra. The results will appear in an upcoming issue of The Astrophysical Journal Supplement.

The Orion Nebula, the nearest rich stellar nursery 1,500 light years away from Earth, provides an unparalleled view of 1,400 young stars, 30 of which are prototypes of the early sun. Scientists have discovered these young stars erupt in enormous flares that outplay anything seen from our sun today in energy, size and frequency.

"We don't have a time machine to see how the young sun behaved,but the next best thing is to observe sun-like stars in Orion," said Scott Wolk at Harvard-Smithsonian Center for Astrophysics.

"We are getting a unique look at stars between one and 10 million years old, a time when planets form," he added.

A key finding is the more violent stars produce flares one hundred times as energetic as the more docile ones. This difference may specifically affect the fate of planets that are relatively small and rocky, like Earth.

"Big X-ray flares could lead to planetary systems like ours, where Earth is a safe distance from the sun," said Eric Feigelson at Pennsylvania State University, the principal investigator for Chandra Orion Ultradeep Project.

"Stars with smaller flares, on the other hand, might end up with Earth-like planets plummeting into the star."

According to recent theoretical work, X-ray flares can create turbulence when they strike planet-forming disks, and this affectsthe position of rocky planets as they form. Specifically, this turbulence can help prevent planets from rapidly migrating toward the young star.

"Although these flares may be creating havoc in the disks, theyultimately could do more good than harm," said Feigelson. "These flares may be acting like a planetary protection program."

About half of the young suns in Orion show evidence of planet-forming disks including four lying at the center of proplyds (proto-planetary disks) imaged by NASA's Hubble Space Telescope.

X-ray flares bombard these disks, likely giving them an electric charge. This charge, combined with motion of the disk andthe effects of magnetic fields, should create turbulence in the disk, the researchers said.

Source: Xinhua



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