NASA's Spitzer Space Telescope has uncovered the darkest cloud of interstellar dust and gas ever seen; it is so dense that even background infrared radiation is blocked, casting an ominous shadow across an otherwise sparkling star field.
Though the cloud may look dark and foreboding, it's future is going to be a lot brighter. The cloud, which is about 50 light-years wide, contains enough mass for 70,000 suns and the region is ripe for the creation of potentially thousands of the most massive O-type stars, providing us with an unprecedented insight to the earliest stages of massive star formation.
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"The map of the structure of the cloud and its dense cores we have made in this study reveals a lot of fine details about the massive star and star cluster formation process," said Michael Butler, a postdoctoral researcher at the University of Zurich in Switzerland. Butler is lead author of the study that has been published in The Astrophysical Journal Letters.
Stars are often born in stellar nurseries where dense clouds of gas and dust collapse under mutual gravity. When the material reaches a certain density, fusion is sparked, forming the cores of baby stars. Clusters of young stars then blast away and consume the remaining stellar material, carving out bright star clusters. Our sun was born in such a cluster but it has since drifted far from its stellar siblings over the billions of years since its early stellar nursery days.
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Although stellar evolution is fairly well understood, the creation of the most massive O-type stars is something of a mystery. O-type stars are at least 16 times the mass of our sun, the biggest can be tens to a hundred solar masses - how do they ‘bulk up' to such extreme masses?
These stars live fast and die young as a consequence, rapidly ending their lives as powerful supernovae. Heavy elements are created in the supernova fireballs, seeding the universe with the elemental building blocks for planets and complex molecules that underlie chemical reactions and, ultimately, life. The formation and life cycle of O-type stars are therefore of the utmost importance for astronomers, hence the excitement surrounding this black cloud located approximately 16,000 light-years away that appears to have enough mass to support O-type star formation.
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"In this rare kind of cloud, Spitzer has provided us with an important picture of massive star cluster formation caught in its earliest, embryonic stages," said astronomer Jonathan Tan, of the University of Florida, Gainesville, and study co-author.
"We still do not have a settled theory or explanation of how these massive stars form," said Tan. "Therefore, detailed measurements of the birth clouds of future massive stars, as we have recorded in this study, are important for guiding new theoretical understanding."