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The Angry Baby Stars of Orion

10 May 2005 (All day)
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Burning bright. The Orion Nebula (left, in infrared light) contains hundreds of young stars that emit surprisingly powerful flares, according to a 13-day exposure in x-rays (right).

Stars in the famed Orion Nebula throw horrid tantrums during their first few million years of life, astronomers have learned. An examination of x-rays from the closest major stellar nursery revealed hundreds of young stars spouting flares that dwarf our sun's biggest storms. Although such flares would be fatal in today's solar system, astronomers think they actually sustain the survival of newborn planets elsewhere by keeping them from spiraling into their parent stars.

Young stars are more active than mature ones. Violent currents of charged gas churn the interiors of new stars, tangling and twisting their magnetic fields. These tangles snap together into new patterns, an explosive process that propels blazing flares of gas and x-rays into space. However, astronomers had not stared at a group of young stars for long enough to know how often these outbursts occurred.

That changed in early 2003, when NASA's Chandra X-ray Observatory studied the crowded star-forming heart of the Orion Nebula for a record 13 days. The sharp-eyed satellite monitored about 1400 new stars, including 27 stars with nearly the same mass as our sun. Chandra saw x-ray pulses thousands of times stronger than those emitted by our sun today, says astronomer Scott Wolk of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. The data reveal that young, sunlike stars emit huge x-ray flares about once each week, Wolk reported today during a NASA conference call with reporters.

The events included "superflares" of more than 100 million °C, arcing far into space and striking disks of gas and dust around the young stars. Those shocks--akin to electrical short-circuits--should stir up the disks, says astronomer Eric Feigelson of Pennsylvania State University, University Park. Theoretical models suggest that such turbulence might jostle the orbits of young planets coalescing within the disks. Without those motions, gravitational interactions with the disk would sap the planets' momentum and doom them to plunge into their stars. "It's possible that the x-rays may protect planets, and specifically may have protected Earth from early destruction," Feigelson says.

Earth's survival shows that some process kept our planet from spiraling too close to the newborn sun, says astronomer Joan Najita of the National Optical Astronomy Observatory in Tucson, Arizona. "Planetary cores can scatter off turbulent fluctuations, somewhat like boats tossed about by waves in a storm," she says. But both Najita and Feigelson agree that theorists still need to explore whether strong x-ray flares were the most important source of that turbulence.

Related sites
Chandra Orion Ultradeep Project
Chandra X-ray Observatory
Background on the Orion Nebula
Star formation primer

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