Cosmic Cloud Poised to Birth Massive Star

PASADENA, CALIF. ? A massive, tranquil object found lurking in a dark cloud in our galaxy could be about to transform into a massive star or stars, giving astronomers their first glimpse at such a region on the cusp of stellar birth.

The cloud, located near the Aquila rift in the galactic plane 23,000 light-years away, has a mass 120 times that of the sun, but it is all compressed into a volume smaller than the Oort cloud of comets orbiting our solar system, astronomers said here today at the 214th meeting of the American Astronomical Society.

The temperature of the cloud is less than -427 degrees Fahrenheit (-255 Celsius).

Massive stars, or those that weigh in at more than eight solar masses, are much rarer than more intermediate-sized, sun-like stars. The stellar whoppers produce much more radiation, causing them to lead short, spectacular lives that end when they die violently in supernova events, explosions that are so luminous they can briefly outshine an entire galaxy.

In their death throes, these stars can quickly destroy any evidence of the environment they formed in, which makes it difficult for astronomers to study the birth of these beasts.

But catalogs of cold, dense gas clouds, such as the new one found with the Submillimeter Array (SMA) atop Mauna Kea in Hawaii, are now giving astronomers a chance to probe regions that look likely to spawn massive stars.

"Perhaps the most exciting thing is that we now know that massive and dense cores with no sign of star formation activity do exist," said team member Jonathan Swift of the University of Hawaii at Manoa.

How massive stars form is a matter of fierce debate.

Studies of nearby star-forming regions show that smaller, sun-like stars form inside dense cores of molecular gas, but whether or not massive stars form in the same manner isn't known.

Some astronomers say that if massive stars were to form in a similar process, their cores would have to hold 100 solar masses of material in a relatively compact volume.

"The mass and density of this object along with the lack of evidence for star formation activity is unique, and this fits very well with our expectations for massive pre-stellar cores," Swift said.

Recent theoretical studies and computer simulations suggest that a core such as this could form massive stars in as little as 50,000 years ? a blink of an eye in the life of the universe.

More study of this region is still needed, Swift noted, and astronomers plan to use the SMA to probe the cloud more deeply.

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