Definitions
from The American Heritage® Dictionary of the English Language, 5th Edition.
- noun A celestial object in a late stage of star formation in which the central condensation resulting from the collapse of a dense, interstellar cloud core has become a sphere that is opaque so that it has a luminous surface like a star, but has yet to sustain nuclear fusion of hydrogen in its core.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun astronomy A collection of
gas anddust inspace with hightemperature that usually grows to the point of beginningnuclear fusion and becoming astar .
Etymologies
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Examples
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Since then, stars have formed by the collapse of small, dense core regions in large, cold protostar, which is hot and bright because of energy generated by gravitational contraction.
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Since then, stars have formed by the collapse of small, dense core regions in large, cold protostar, which is hot and bright because of energy generated by gravitational contraction.
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Another unsurprising confirmation of stellar formation models is that forming cores in the nebula are notably warmer when they've reached the density sufficient to create fusion in the core and have an embedded protostar.
New Studies on the Vela Star Forming Region | Universe Today 2010
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The presolar nebula's contraction, the outward pressure of the protostar, then of the sun, and the rotation of the entire ensemble led to a complicated dance of creation.
‘The Fallen Sky: An Intimate History of Shooting Stars' 2009
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It took some 10,000 years for outward gas pressure to balance against gravitational contraction, then another 10 million years for the protostar to condense just enough to create what became our sun, whose interior pressures forced a sustained hydrogen fusion reaction at 10 million degrees.
‘The Fallen Sky: An Intimate History of Shooting Stars' 2009
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With this new movie, we can see changes over just a few months as gas clumps swarm around this young protostar, added Smithsonian astronomer and co-author Ciriaco Goddi.
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"The bending path of these masers provides key evidence that magnetic fields may be influencing gas motions very close to the protostar," pointed out Claire Chandler of NRAO, a co-principal investigator of the study.
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The heart of the presolar nebula began to quicken, and within a few thousand years a protostar — not yet fusing hydrogen — went through phases of contraction, expansion, and varied brightness.
‘The Fallen Sky: An Intimate History of Shooting Stars' 2009
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Some masers were as close to the protostar as Jupiter is to our Sun, which is also a record.
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The resulting movie reveals signs of a rotating accretion disk, where gas is swirling closer and closer to the protostar at the center.
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