How Much Stuff Do You Need?

In order to get fusion going, you need like at least like 80 times the mass of jupiter. You can get clumps forming that are smaller than that, they just won't necessarily start fusion. But typically, these clouds where stars are formed are like a thousand light years long. And inside that you have like denser regions, which astronomers refer to by the technical word clumps. And then inside that are like, slightly denser regions they call cores. And that's usually where stars are actually formed.