A series of ‘black dwarf’ supernovae will be the last astrophysical events occurring in our Universe prior to the so-called hot death, when the Universe will be populated only by black holes and ‘frozen’ white dwarfs, according to a paper of Illinois State University Theoretical Physicist Matt Caplan.
In the distant future, long after star formation has ceased, the Universe will be populated by sparsely degenerate remains, mostly white dwarfs; these white dwarfs cool and solidify solidly in black dwarfs. Image credit: Goddard Space Flight Center from NASA / S. Wiessinger.
‘It’s going to be a bit of a sad, lonely, cold place. No one will be there to witness this long farewell that will happen in the distant future. Most believe that everything will be dark when the universe comes to an end, “said Dr. Caplan.
“Puncture of darkness could be silent fireworks – explosions of the remains of stars that would never explode.”
In the Universe now comes the dramatic death of massive stars in supernova explosions as internal nuclear reactions produce iron at the core.
Iron cannot be burned by stars – it accumulates as a poison, causing the star to collapse and create a supernova.
But smaller stars tend to die with a little more dignity, shrinking and becoming white dwarfs at the end of their lives.
“Stars less than about 10 times the mass of the sun have the weight or density not to produce iron in their nuclei like mass stars do, so they can not currently explode in a supernova,” said Dr. Caplan.
“While white dwarfs will cool down for the next few trillion years, they will dimmer, eventually freeze and become ‘black dwarf’ stars that no longer shine.”
Like modern white dwarfs, they are mostly made of light elements such as carbon and oxygen and are about the size of Earth, but contain about as much mass as the Sun, their inside millions of times larger than close to Earth.
But just because they are cold does not mean that nuclear reactions stop.
“Stars shine because of thermonuclear fusion – they are hot enough to merge small nuclei to form larger nuclei, which releases energy,” said Drs. Caplan.
“White dwarfs are like, they’re burnt out, but fusion reactions can still happen because of quantum tunneling, only much slower.”
“Fusion happens, even at zero temperature, it just takes a long time. This is the key to turning black dwarfs into iron and triggering a supernova. ”
In his paper, Drs. Caplan how long do these nuclear reactions take to produce iron, and how many iron black dwarfs of various sizes must explode.
He calls his theoretical explosions black dwarf supernovae and calculates that the first in about 10 will occur1100 years.
‘In years, it’s like the word’ trillion ‘being said almost a hundred times. Once you have written it out, it will take up most of a page. It’s mindbogglingly far into the future, “said Dr. Caplan.
‘Of course, not all black dwarfs will explode. Only the most massive black dwarfs, about 1.2 to 1.4 times the mass of the Sun, will blow. ”
Yet that means that as many as 1% of all the stars that exist today, about one billion trillion stars, can expect to die this way. As for the rest, they will remain black dwarfs.
“Even with very slow nuclear reactions, our Sun does not have enough mass to ever explode in a supernova, even in the distant future. You could turn the whole Sun around iron and it would still not pop, “he said.
He estimates that the most massive black dwarfs will explode first, followed by progressively less massive stars, until after about 10 there are no more left to go.32000 years.
At that point, the Universe can be truly dead and silent.
‘It’s hard to imagine that coming after that, black dwarf supernova is the last interesting thing that can happen in the Universe. They could be the last supernova ever, ”said Dr. Caplan.
By the time the first black dwarfs explode, the Universe will already be unrecognizable.
“Galaxies will have scattered, black holes will have evaporated, and the expansion of the Universe will have pulled all the remaining objects so far apart that no one will ever explode any of the others,” said Dr. Caplan.
“It will not even be physically possible for light to travel that far.”
‘Maybe we should try to simulate some black dwarf supernova. If we can not see them in the air, then at least we can see them on a computer. ‘
The paper of Dr. Caplan was published this month in the Monthly announcements from the Royal Astronomical Society.
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ME Caplan. Black dwarf Supernova in the distant future. MNRAS, published online August 7, 2020; doi: 10.1093 / mnras / staa2262
