It stops contracting, since the energy it radiates is supplied by nuclear fusion, and need not be supplied by contraction. The main sequence When it arrives on the main sequence, a star's composition is essentially uniform throughout. The star's structure has to change to accommodate this new outpouring of energy, and its peaceful life on the main sequence comes to an end. The surface grows cooler, but overall the luminosity of the star goes up, and it becomes a red giant. See Table 16-1 on page 328.
More massive stars can lose mass spectacularly as supernovae.
Initially called a white dwarf, such objects will cool in the fullness of time to become black dwarfs. This pressure is also proportional only to density, and thus the so-called neutron star can cool off. If the remnant mass is greater than 3 or 4 solar masses, the collapse continues. These phenomena are due to a distortion of spacetime in the vicinity of the hole. Copyright 1999 by James N. Douglas.