Why do we think a stars are like a dense gas?

Answer 1

We've looked at the spectra of many stars and based on the absorption lines the spectra, we identified the gasses. In fact we discovered helium that way and finally found it on the earth over hundred years later. So Gene is right...!!!

Answer 2

We don't think, we know (as much as we can know such things, short of going there and trying to dig up with a shovel), since the light coming from the stars is having the same wavelengths as the light coming from our own sun and we know that the temperature on the surface of the sun is about 6000 degrees and it can only increase further as we go deeper and we also know that no known substance can exist at that temperature as solid or liquid.

Answer 3

We've looked at the spectra of many stars and based on the absorption lines the spectra, we identified the gasses. In fact we discovered helium that way and finally found it on the earth over hundred years later