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How do stars form from interstellar medium

How do stars form from interstellar medium - • Further...

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How do stars form from interstellar medium? Protostars form in cold, dark nebulae (molecular cloud) Star formation begins in dense, cold nebulae, gas needs to be as cold as possible, where gravitational attraction causes a clump of material to condense into a protostar These region of cold dust and gas are known as Barnard Objects, smaller spherical dark nebula are called Bok Globules. Each Barnard object contains several thousand solar masses of dust and gas spread out over a volume of about 30 pc. As a protostar grows by the gravitational accretion of gases, Kelvin-Helmholtz contraction causes it to heat and begin glowing. Protostars evolve into main-sequence stars A protostar’s relatively low temperature and high luminosity place it in the upper right region on an H-R diagram.
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Unformatted text preview: • Further evolution of a protostar causes it to move toward the main sequence on the H-R diagram • When its core temperatures become high enough to ignite steady hydrogen burning, it becomes a main sequence star. • The more massive the protostar, the more rapidly it evolves. • During the birth process, stars both gain and lose mass • In the final stages of pre–main-sequence contraction, when thermonuclear reactions are about to begin in its core, a protostar may eject large amounts of gas into space • Low-mass stars that vigorously eject gas are called T Tauri stars • A circumstellar accretion disk provides material that a young star ejects as jets • Clumps of glowing gas called Herbig-Haro objects are sometimes found along these jets and at their ends...
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