The end of the universe won’t be particularly eventful. Most of the stars will slowly cool down to zero. It’s slowly being the keyword here.
" It will be a rather sad, empty and cold place, " says Matt Caplan, adding that this end of the universe will not be seen anyway. Most scientists believe that the end will be dark and the universe will experience a so-called heat death. This is when the universe will be mostly filled with black holes and burned-out stars, adds Caplan, who expected a different result when he calculated how these extinct stars would change over the next eons.
What will the end of the universe be like?
The total darkness will be lit from time to time by silent fireworks – explosions of extinct stars that were never intended to explode. In a recent theoretical paper, Caplan, an associate professor at the University of Illinois, writes that many white dwarfs could explode as supernovae in the distant future, long after all other objects in the universe have died down and died out.
In the present universe, the dramatic death of massive stars in a supernova explosion occurs when nuclear reactions inside the star lead to the production of iron in the core. Stars are unable to use iron as fuel, and it begins to accumulate like poison, which over time causes the star’s core to collapse and explode in a supernova. However, less massive stars die more peacefully, shrinking into white dwarf stars towards the end of their lives.
Black dwarfs – their era has not yet come
Stars with a mass less than 8 times the mass of the sun are unable to synthesize iron in their core as massive stars do, and therefore will not explode as supernovae. As white dwarfs gradually cool down over the next trillions of years, they will get darker and darker until they eventually freeze, become black dwarfs and stop shining, says Matt Caplan.
Similar to white dwarfs today, such black dwarfs will be composed of light elements such as carbon and oxygen and will be the size of the Earth and the mass of the sun. It also means that their density will be millions of times greater than that of anything on Earth.
The fact that black dwarfs are getting cold at this point does not mean that nuclear reactions are stopping inside them. Stars glow as a result of a fusion reaction in which elements are converted into others, releasing enormous amounts of energy. White dwarfs are already ash, they are burned out, but fusion reactions can still take place in them due to quantum tunneling. However, they are much slower. The fusion can take place even at zero temperature, but then it takes a really long time. According to Caplan, this is crucial information for turning black dwarfs into iron and leading to a supernova.
Exploding black dwarfs – new supernovae
In a recent article published in the Monthly Notices of the Royal Astronomical Society, Caplan calculates how long these nuclear reactions take to produce iron, and how much iron black dwarfs of various sizes need to explode.
According to calculations, the first supernova explosion triggered by the black dwarf will take place in about 10 ^ 1100 years. If we wanted to write this number in plain type on a piece of paper, it would take up almost a full page.
Of course, however, not all black dwarfs will explode. Only the most massive black dwarfs, with a mass of 1.2 to 1.4 solar masses, will explode. Even so, it means that up to 1 percent of all stars in existence today, or some one billion trillion stars, will die this way. The rest will remain black dwarfs.
Even with very slow nuclear reactions, the Sun is too light to explode as a supernova, even in the very distant future. The whole sun could be turned to iron and cut so that it wouldn’t explode.
Caplan predicts the most massive black dwarfs will explode first, followed by the same path less and less massive. The last one will explode in about 10 ^ 32,000 years. At this point, after the last supernova, the universe will be really dead and silent.
It is hard to imagine what will happen next. The last black dwarf supernova will be the last interesting event in the universe. It doesn’t change the fact that by the time it comes to the first black dwarf supernova, the universe will no longer resemble the present one. Galaxies will long since fall apart, black holes will evaporate, and expanding the universe will distance all objects far enough from each other that none of them will be able to see the others explode.
However, he is not discouraged by:
I became a physicist for one reason. I wanted to find answers to the big questions – why does the universe exist or how it will end. What now? Perhaps we will try to simulate a supernova explosion from a black dwarf. If we cannot see them with our own eyes, maybe at least on a computer screen? Caplan says.
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An exploding black dwarf will be the last interesting event in the universe. Then there will be total darkness