How does star-making start? For first time, scientists might get a glimpse.
Scientists have yet to see a star form all on its own – away from the influence of surrounding stars. Now, researchers say they might have found a candidate.
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Scientists offer explanations for how conditions in a pristine clump of gas can influence the formation of fragments.Skip to next paragraph
In Pictures Where stars form
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Turbulence within the clump can lead to regions with higher densities than others. These regions become the fragments, which begin to collapse under their own gravity, gathering additional gas and dust from their surroundings as they grow. At some point, a fragment becomes so dense that it begins to heat. Eventually temperatures rise to the point where atoms in the core fuse, releasing enormous amounts of energy. The star is born.
But magnetic fields within a molecular cloud could also delay the collapse of a cloud fragment into a stellar core, some researchers hold. Although the cloud is laced with electrically neutral molecules, it also contains electrically-charged particles. These respond to magnetic fields in the cloud. If a fragment is in a region of its parent cloud where magnetic fields are strong, these fields can exert an outward pull to counteract gravity's inward tug on the fragment, Di Francesco explains.
The fact that stars exist, he adds, would testify to a threshold beyond which gravity wins.
While the team has no way to measure magnetic fields in the fragments' host clump, the researchers suggest that such fields may be the reason why B1-E isn't as far along in its star-forming activity as are other regions of the Perseus molecular cloud.
Search for a star-in-waiting
The team used the European Space Agency's Herschel infrared observatory, launched in May 2009, to make its initial observations of B1-E. The broad clump yielded evidence of nine fragments. They tipped the scales at from 0.3 to 1.6 times the mass of the sun and ranged in size from just over 5 AU to 9 AU. One AU, or astronomical unit, is 93 million miles – the average distance at which Earth orbits the sun.
The team then turned to the US National Radio Astronomy Observatory's 100-meter dish telescope at Greenbank, W. Va. to determine the motions of these objects. They used the spectrum of an ammonia molecule as a speedometer. Ammonia is a common component of molecular clouds. In a fragment where ammonia was speeding away at high relatively velocity, gas and dust could be collapsing to form a stellar core, the team suggests.
“Based on the variety of the velocities we could see, there was one location that seemed to be well on its way to forming a core, “ Dr. Di Francesco says. “The others may still be sloshing around in the clump. Some may still grow. Some may disperse.”
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