protostar

American  

[proh-toh-stahr] / ˈproʊ toʊˌstɑr /

noun

Astronomy.

1. an early stage in the evolution of a star, after the beginning of the collapse of the gas cloud from which it is formed, but before sufficient contraction has occurred to permit initiation of nuclear reactions at its core.

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protostar British  

/ ˈprəʊtəʊˌstɑː /

noun

1. 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

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protostar Scientific  

/ prō′tə-stär′ /

1. A celestial object made of a contracting cloud of interstellar medium (mostly hydrogen gas) that eventually becomes a main-sequence star. Disturbances in some region of interstellar medium can cause fluctuations of density through that region, and the denser areas, having more mass, begin to attract more and more of the medium through the force of gravity (a process known as accretion). Ever increasing densities of such protostar regions lead to ever higher temperatures within the accreting body, until the point is reached when thermal energy is sufficient to promote the fusion reactions typical of main-sequence stars. Less massive protostars may take hundreds of millions of years to evolve into stars; massive ones contract more quickly and may take only a few hundred thousand years.

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Etymology

Origin of protostar

First recorded in 1945–50; proto- + star

Example Sentences

"It's all thanks to JWST's exceptional sensitivity combined with high angular resolution that we're able to detect these faint spectral features associated with ices around such a distant protostar," Sewilo said.

From Science Daily • Nov. 12, 2025

According to NASA, this "suggests that the protostar may in fact be an unresolved binary star," meaning there could actually be two stars beneath this mysterious cloud of molecules.

From Salon • Sep. 14, 2023

This is an outflow of material from a protostar called LVA1623.

From BBC • Jul. 12, 2023

For a massive protostar - more than 8 times heavier than our Sun, the flow of nutrients is not continuous.

From Space Scoop • Mar. 29, 2023

I didn’t think my skin could get any redder than it was, but I was pretty sure I had started glowing like a protostar about to undergo its first burst of fusion.

From "Darius the Great Is Not Okay" by Adib Khorram