# How stars get their mass.

1. Oct 19, 2010

### discord73

If Hydrogen fusion starts around 100JM (Jupiter Masses) then how do the larger stars get so massive? I was watching The Universe and it said some stars are over 200 solar masses and higher. How can a star get so massive?

2. Oct 19, 2010

### cepheid

Staff Emeritus
Well, what the start of hydrogen fusion really depends upon is temperature. If the core temperature is high enough, fusion will occur. I suppose it is possible that 100 MJup is the least massive object for which this can be the case, but I have to admit I am unsure.

I'm not totally sure what you're asking here. You realize it is possible for matter to continue to accrete onto a protostar? If your question is, "what determines the masses with which stars will form?", then I think the answer might be "nobody knows for sure." People have ideas. There is the idea that there might be some dependence upon environment. For instance, in a dense environment, more matter can continue to accrete, causing the central temperature to get higher before hydrostatic equilibrium is achieved. In a less dense environment, maybe hydrostatic equilibrium is achieved at a lower mass. In any case, high mass star formation is particularly puzzling. People are not sure whether this accretion picture is accurate, or whether the highest masses of stars need to form by coalescence (i.e. by the merger of several lower mass stars that are in the process of formation).

I am pretty sure that around 100 Msun is the upper limit beyond which a star begins to blow itself apart (i.e. blow away its outer layers) due to radiation pressure (because the more massive a star is, the more luminous it is).