Some gas clouds refuse to collapse

Cold dust found near star-forming regions

CLOUD SPOTTING  Temperature (left) and brightness, as measured by 450-micrometer radiation (right), revealed dust in a large cloud of interstellar gas. The cold temperatures measured at the cloud’s center indicate the gas has not begun collapsing into a star.

G. Sreenilayam et al/Astronomical J. 2014, reproduced by permission of the AAS

Like character actors and perpetual opening acts, some interstellar gas clouds never quite become stars. Astronomers have substantially expanded the number of these elusive clouds known to exist near hot star-forming regions in the Milky Way.

Stars form when enormous gas clouds collapse under their own gravity and hydrogen atoms begin fusing into helium. But without fusion’s heat, galactic clouds are cold and sparse, and are difficult to find.

Seeking cold gas clumps, a team led by astrophysicist Michel Fich of the University of Waterloo in Canada and astrophysicist Gopika Sreenilayam looked instead for dust particles. Because the particles are thousands of times larger than gas molecules, dust mixed in the clouds is easier to see. Using two infrared cameras on the James Clerk Maxwell Telescope in Hawaii, the team found 20 dense gas clouds whose centers have temperatures from 8 to about 20 kelvins. At those temperatures, the clouds are too cold to collapse into stars. The researchers report the findings in the March Astronomical Journal.

Studying these gas clouds could help astronomers better understand what prevents the clouds from collapsing. Possible explanations include magnetic fields and turbulence within the clouds.

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