White Dwarf’s Shrink When They Gain More Mass

White Dwarf’s shrink when they gain more mass

Many white dwarf stars have companion stars. What was once a binary pair of stars, one star exhausts its fuel and after being a red giant, sheds its outer shell and collapses into a white dwarf. Often the companion star is far enough away to not be a problem, but from time to time, they are close enough for an exchange of material, particularly if the partner star bloats to become a red giant. The white dwarf begins to snack on the material from the partner star.

Now, you’d imagine the white dwarf would then grow in size, but rather, it shrinks ! 

It’s not the size that denotes the amount of material, it’s the mass, and as the mass increases, so does the gravitational effect, and the matter is then crushed further down. 

As the gravitational pull increases, it is possible that the now dead star can gain enough pressure at the centre to re-ignite fusion of carbon and oxygen, and it turns out that the mass required to do this, sits very close to the limit where neutron stars are formed. So suddenly a huge portion of the carbon and oxygen begins to fuse, and causes a huge explosion of energy. so much so, that most supernova explosions will output more energy in that one event, than our sun will in it’s entire 10 billion years of main sequence life.