How big does a gas giant have to be in order to ignite and become a star?

Morningfox say: When more mass is added to something like Jupiter, it doesn't get much bigger. In fact, at some point it can actually shrink. It just gets more massive and denser, with more pressure at the core. Eventually with enough mass, the core starts nuclear fusion and becomes a star.
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CarolOklaNola say: A minimum of 60 of jupiter masses. I assume you mean the minimum mass required to become red dwarf star in hydrostatic equilibrium on the main sequence, Not a brown dwarf star of any spectral classification that cannot maintain fusion in the core long enough to move onto the man sequence.. Neither Jupiter nor Saturn have enough mass and have NEVER had enough mass to become stars.

it makes total logical sense.

You are confusing MASS with SIZE, VOLUME and DENSITY , The three physical properties are NOT NECESSARILY CORRELATED.


"..."Star Formation." World Book Encyclopedia. So-Sz Volume18. Chicago: World Book1989: 849. "The kind of star that takes shape depends on the mass of the contracting cloud. A cloud with mass about 1/20 that of the sun becomes a red,low-luminosity main sequence star." 0.05 solar mass
Cohen, Martin. In Darkness born - The Story of a Star Formation.Cambridge University Press, 1988: 37. "Both theory and observations concur in defining a minimum protostellar mass for the ignition of the hydrogen fusion to be around 0.08 solar mass. (Jupiter and Saturn for comparison with this limit, are only 0.001 and 0.0003 solar masses)." 0.08 solar mass
Wagner/Goldsmith. Cosmic Horizons - Understanding the Universe.The Portable Stanford, 1982: 82. "Why do all stars have masses not greatly different from that of the sun? Calculations show that balls of gases with less than about 1/10 of the sun's mass cannot produce (through self gravitation) a central temperature hot enough to ignite nuclear reactions." 0.10 solar mass...