Black dwarf explosion could be the ‘last interesting thing to happen in the universe’

“This is how the world ends,” TS Elliot said in his famous poem, “Not with a bang but a moan.” These days, scientists regard the heat death of the universe as the moaning, but a new theoretical analysis predicts the cosmos will breathe its last breath in the form of black dwarf explosions.

Billions and trillions of years from now, long after the last stars have gone extinct, the heaviest black dwarfs will begin to supernova, according to the new research published in the Monthly Notices of the Royal Astronomical Society. Black dwarfs are the frozen remains of white dwarfs, which are themselves the remnants of low mass stars. The study’s only author, astrophysicist Matt Caplan of Illinois State University, says these explosions will be “the last interesting thing to happen in the universe” because he Explain in an ISU press release.

The universe could end in many ways, but the best guess now is that it will continue to grow long after everything in it has been torn to shreds, including galaxies, solar systems, stars, and even atoms. By the time the black dwarves are ready to appear, the universe will be “cold and lifeless,” Caplan wrote to me in an email.

“The expansion of the universe will long ago have separated all remaining objects by distances so enormous that no light will ever be able to reach from one to the other,” he said. “Each object will end up in a universe completely devoid of anything else in all directions. It will be cold and close to absolute zero. “

When existing stars become supernovae, it is because of an excess of iron in their nucleus – the result of internal nuclear reactions. The same cannot be said of smaller stars, which eventually burn and shrink into white dwarfs. According to the theory, white dwarfs will eventually lose their luster and freeze in the distant future, becoming black dwarfs.

“Without a heat source, they just cool down for all eternity, until they turn ‘black’ and no longer glow,” said Caplan. “It’s like taking a hot pan out of the oven – all it can do is cool it down.”

These hypothetical objects would be roughly the size of Earth, but with masses close to that of our Sun. Importantly, nuclear reactions will still occur within these dense, frozen worlds, but at rates noticeably slower than normal. And as the new study predicts, these reactions will result in a steady build-up of iron, albeit over cosmologically large time scales. With that in mind, Caplan analyzed the numbers to estimate how long it will take for these black dwarfs to produce enough iron to trigger a supernova explosion.

The answer, at 10^1,100 years, is “extremely long,” said Caplan. The age of the universe itself is closer to 10^ten years, so if you were to try to write 10^1,100 it would contain 1,100 zeros and “take up most of a paragraph,” he explained. Or as Caplan put it in the ISU statement, “It’s like saying the word ‘trillion’ almost a hundred times.”

Importantly, these explosions will only occur among the largest of black dwarfs, namely those about 1.2 to 1.4 times the mass of the Sun. These supernovae – the last to occur in the universe – will eventually stop around 10^32,000 in a few years, after which the cosmos will truly be a calm and uneventful place.

Caplan said his analysis took into account the effects of an expanding universe. However, “if dark energy is different from what we currently suspect, then the expansion of the universe could destroy black dwarfs long before they have a chance to explode,” he said. declared. Additionally, Caplan’s calculations were based on our current understanding of nuclear physics, astrophysics, and cosmology, but to be fair, scientists cannot be certain if the laws of physics and universal constants will remain. the same in the distant future. It is possible, for example, that the universe will not even exist at this future stage.

“Some theories in particle physics predict that the proton is fundamentally unstable and will decay, although this has not yet been observed or confirmed. If that’s the case, then all of the material is going to sort of ‘evaporate’ long before the black dwarfs explode, ”Caplan said. “This is just one example. In a sense, our understanding of the far future depends entirely on our understanding of the laws of physics today, and small changes in physics as we know it can have huge consequences for the ultimate fate of the world. universe and its contents.

Although Caplan said that these black dwarf supernovae would be the “last interesting thing to happen in the universe,” we asked him if anything of importance or of interest could happen after this phase.

“It depends on your definition of interesting,” he says. “If a cold iron ball floating around in a universe where it is completely causally separated from all other objects is ‘interesting’, then I guess you might find something interesting.

Okay, good point. But if there is any consolation in all of this, it is that the universe will continue to expand forever, at least according to some theories. It will be dead, cold and lifeless, but at least it will always be there.