Star formation question

[gaseous]

Possibly a silly question that hopefully some of the smart folks on here can answer. If a protostar/brown dwarf gains enough mass to initiate nuclear fusion in its core and become a star, how long does it take for the “starness” to become apparent? Given that it can take 100,000 years for a newly-minted photon to travel from the core of a star to the surface, would that then imply that a star might take 100,000 years to visibly “switch on” after nuclear fusion has commenced?

[billdan]

Hi Patrick

I'm not an expert, but from what I remember Brown dwarfs are the same size as Jupiter but have more mass and generate more heat than what Jupiter does and they are visible in Infrared only. For the dwarf to start the fusion of Hydrogen its diameter would have to increase at least 10 times or more, in which case it would no longer be called a brown dwarf.

As for the 100,000 years for light to pass through the star, I believe that figure is for our Sun, so it would vary depending on the final diameter of the Star.

Cheers
Bill