protostar

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Related to Proto star: Life cycle of a star

pro·to·star

 (prō′tə-stär′)
n.
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.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

protostar

(ˈprəʊtəʊˌstɑː)
n
(Astronomy) a cloud of interstellar gas and dust that gradually collapses, forming a hot dense core, and evolves into a star once nuclear fusion can occur in the core
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014