A theoretical physicist named Dr. Matt Caplan from Illinois State University has worked to determine when the last supernova ever will occur. He says that the universe in the distant future will be a “sad, lonely, cold place.” Caplan says that most scientists believe that all would be dark when the universe comes to an end in a phenomenon known as “heat death.”
In the far far future, most envision the universe as mostly black holes and burned-out stars. However, he says that many white dwarf stars could explode in a supernova in the distant future, long after everything else has died and gone quiet.
Typically, only massive stars end their lives in a supernova explosion. Smaller stars tend to shrink and become white dwarfs near the end of their lives. Caplan says that stars less than about ten times the mass of the sun lacked the gravity or density to produce enough iron in their core the way more massive stars can and can’t explode in a supernova in the current universe.
He says that over the next few trillion years as white dwarfs cool down, the grow dimmer and eventually freeze solid becoming black dwarf stars that no longer shine. They’ll be mostly made from carbon and oxygen and will be the Earth’s size but contain as much mass as the sun. There is a method that these black dwarf stars can use to go supernova.
The scientist says that fusion happens even at zero temperature thanks to quantum tunneling, it just takes a long time. He does note that not all black dwarfs will explode, only the most massive. A black dwarf will need about 1.2 to 1.4 times the mass of the sun to explode, meaning only 1% of all stars that exist today. While that percentage seems low, that’s about a billion trillion stars.