HUNDREDS of bright X-ray beacons have turned up unexpectedly in a nursery of
newborn heavyweight stars. Astronomers say the sources, captured in images from
NASA’s Chandra X-ray satellite, strike a blow to their understanding of these
hot spots.
“Life in these areas is much more complicated than we thought,” says Ed
Churchwell of the University of Wisconsin at Madison.
Churchwell used Chandra to look at a region of the sky 6000 light years away
where around a dozen stars, up to about 100 times the mass of our Sun, are
forming. He expected to see strong X-rays from each star because they emit
super-hot winds of 100 million °C that plough into surrounding gas and dust.
“We hoped to see around 15 or 20 of these,” says Churchwell. But instead, he saw
around 300. “It just blew my socks off.”
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At a meeting of the International Astronomical Union in Manchester this
month, Churchwell said the sources are unlikely to be additional massive stars,
because they aren’t emitting the characteristic radio waves. The X-rays might
come from colliding stellar winds of pairs of massive stars in close orbits, or
black holes gobbling up stars. But the sheer numbers would still be difficult to
explain. Alternatively, the X-rays might come from very young low-mass stars,
but normal stars are not usually hot enough to emit such energetic X-rays. So
far astronomers are baffled.
“If this is true for this region, it’s probably true for others, and that’s
really surprising,” says Mordecai-Mark Mac Low, an astrophysicist at the
American Museum of Natural History in New York. Understanding such star
factories is crucial to understanding galaxies, he adds.