Matt Caplan, a theoretical physicist at Illinois State University, has calculated when the last supernova will happen in the universe. And he said that afterward, the universe will become a 'bit of a sad, lonely cold place'.
Massive stars explode into supernovas after a certain amount of iron accumulates at their cores. But smaller stars like white dwarfs- extremely dense stellar objects that form when sunlike stars run out of nuclear fuel- have neither the gravity nor the density to produce iron. But this may not always be the case. Caplan says that these white dwarfs may increase in density over time until they end up becoming 'black dwarfs' and produce iron that may one day allow them to explode like their massive cousins.
"As white dwarfs cool down over the next few trillion years, they'll grow dimmer, eventually freeze solid, and become 'black dwarf' stars that no longer shine," says Caplan. "Stars shine because of thermonuclear fusion — they're hot enough to smash small nuclei together to make larger nuclei, which releases energy. White dwarfs are ash, they're burnt out, but fusion reactions can still happen because of quantum tunneling, only much slower."
Quantum tunneling happens when subatomic particles 'tunnel' through a barrier that otherwise seems impossible to penetrate. And this process, Caplan says, maybe the golden ticket for white dwarfs to transform into black dwarfs and explode into supernovas.
As such, in his new study, Caplan calculated how much iron these black dwarfs would need to explode. And in doing so, he found that the first of the 'black dwarf supernovas' will explode in 10 to the 11,000 years. An almost unimaginable figure, he says it's like saying the word 'trillion' nearly a hundred times. Either way, the first of these explosions is to be extremely far in the future.
He also found that black dwarf explosions will begin in descending order- largest first- until none are left, something he expects to happen in 10 to the 32,000 years. And he says that he may be the last 'interesting thing' that the universe will experience- or at least, the last supernova.
It as at this point, after this last explosion, that the universe will allegedly become a sad, lonely place. He said, "Galaxies will have dispersed, black holes will have evaporated, and the expansion of the universe will have pulled all remaining objects so far apart that none will ever see any of the others explode. It won't even be physically possible for light to travel that far."
Sources: Oxford Academic, Space.com, Stargazing UK