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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