A Hot Stellar Womb

Blaze of glory. An embryonic star hidden within the brightest cloud of gas and dust churns out fierce x-rays.

Baby stars emerge from surprisingly active wombs, a new study shows. Satellites have detected intense x-rays blazing from the youngest stellar embryo yet seen, an object perhaps 10,000 years old. The x-rays suggest that magnetic fields force matter to plunge toward the developing star at high speeds, creating temperatures up to 50,000,000°C.

It takes millions of years for a cloud of gas and dust to create a newborn star. Matter at the core of the "protostar" must pack tightly enough to ignite the nuclear reactions that power all young stars. For decades, astronomers assumed that gravity was calmly contracting cocoons of cold matter into denser and denser balls. But several years ago, newly launched satellites spotted x-rays from star-forming clouds at ages of just 100,000 years--long before fusion begins. Astronomers suspected that magnetic fields were sparking hot flares deep within these clouds (ScienceNOW, 14 November 2000).

The new research suggests that x-rays start sizzling from embryonic stars at an even earlier stage of their growth. A team led by astronomer Kenji Hamaguchi of NASA's Goddard Space Flight Center in Greenbelt, Maryland, used the XMM-Newton and Chandra x-ray satellites to study a stellar nursery just 550 light-years from Earth. The astronomers saw a distinct x-ray signal from an object embedded within a dense knot of dust. So much dust shrouds the protostar that its age can't be much more than 10,000 years, the team calculates. The energy levels of the x-rays point to gas cascading onto the growing star at a speed of about 3000 kilometers per second, says Hamaguchi. Gravity alone could not pull gas inward so quickly, he notes. "We think magnetic activity plays an important role," Hamaguchi says, with temperatures reaching 40,000,000 to 50,000,000°C. The team's report will appear in next month's Astrophysical Journal.

The paper makes a compelling case that the protostar is the youngest ever seen to emit x-rays, says astrophysicist Norbert Schulz of the Massachusetts Institute of Technology in Cambridge. "If that's really true, it is indeed a milestone." However, he believes it remains possible that the object is closer to 100,000 years old and that magnetic fields were not accelerating gas inward during its first 10,000 years.

Related sites
Abstract of paper, with link to full text
Japan's Subaru Telescope in Hawaii, with images of protostar
XMM-Newton Observatory
Chandra X-ray Observatory
Background on star formation

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