When the last star in the universe dies, there will be no more stars in the sky, and the universe will become a cemetery, scattered with the remains of dead stars. The sun would turn into a white dwarf, a hot and dense corpse, and slowly he would become dim, the last bit of residual heat before he extinguished. If we look at it from where we are now, he will not be brighter than the full moon in the clear night sky, and the faint return light of a white dwarf will be the only light in a universe full of dead stars and black holes.
It would be a ghostly universe, dotted with corpses and wreckage of stars.
white dwarf
Eventually, gravity will pull these wreckage out of the original stars and throw them into the icy night. If you're lucky, some brown dwarfs may collide and form new stars. Occasionally, colliding neutron stars also emit a supernova explosion in the dark of night. Those who survive may find refuge around old white dwarfs. But eventually, white dwarfs will also go out, and all stars will eventually become black dwarfs, which are white dwarfs that can no longer emit light. A black dwarf is a decaying, dark, dense, degenerate mass of matter that is the last life stage of a star, and the atoms that make up a black dwarf are densely squeezed together, a million times denser than the Sun.
It takes a long time for stars to become black dwarfs, and we believe that black dwarfs do not currently exist in the universe.
black dwarf
All matter that has not been thrown out of the original galaxy will be swallowed up by the black hole in the center of the galaxy. Outside the sleeping black hole, leaving a glow, the energy belt around the black hole will become the last source of energy for future civilizations.
The rhythm of our lives is determined by the energy available, and imagining our lives and consciousness has a very different speed than it is now. Much slower than it is now, in that environment, perhaps every 10 trillion years an idea will arise, and it is not difficult to imagine that even if humanity goes extinct, in the distant future, there may be intelligent beings, even if it is very short, so that intermittent civilizations will appear.
The universe is expanding faster and faster, even faster than the speed of light. By then, galaxies and stars will be speeding outward at a faster speed than they can ever capture the light they emit. The secrets of the universe will never be solved again. Existing theories speculate that atoms decay, leading to the destruction of all matter in the universe. Protons, which make up the main components of atoms, may spontaneously begin to decompose, and all the material that avoids black holes will eventually disappear due to proton decomposition.
The End of Time: The End of the Universe (II)