I'd assume much bigger. NEED MORE MASS! MUST CONSUME HUGE QUANTITIES!.....
How much bigger would it need to be to ignite? Then it would just be another young star.
I'd assume much bigger. NEED MORE MASS! MUST CONSUME HUGE QUANTITIES!.....
“For stars with similar metallicity to the Sun, the theoretical minimum mass the star can have, and still undergo fusion at the core, is estimated to be about 75 times the mass of Jupiter.”
This one is six times the mass of Jupiter, so maybe 12.5 times larger to ignite, rough estimate.
I don’t even know if it is possible for planets to become stars, even gas giants with the right composition. Stars are thought to form from interstellar gas clouds that become dense enough to start collapsing gravitationally. A planet has already coalesced to a gravitational equilibrium, so I think it’s too late at that point.
It would take roughly 65 Jupiter masses (or 0.1 solar masses, some say 0.08 solar masses) for p-p chain initiation. Brown dwarves as low as 15 Jupiter masses can burn deuterium and lithium, but will quickly exhaust that fuel since it is only a small percentage of the mass of the brown dwarf (still mostly hydrogen). Six Jupiter masses would not be sufficient to ignite, so much of the heat is due to continuing gravitational contraction, coupled with the thermal mass. The same applies to Jupiter and most other gas giants.