The universe is slowly dying, but humans can survive as long as we have an energy source. The universe will die over many billions of years, but on a universal time scale, stars like our Sun will be gone in no time. However, there are places that will exist practically forever from a human perspective: the corpses of dead stars, or white dwarfs. These could be humanity's last home right before the death of the universe.
Stars live for varying lengths of time, depending on their mass. Massive stars burn hot and fast, dying violently in supernovae within a few million years. However, the majority of stars, 97%, will end their existence as white dwarfs. Small stars, or red dwarfs, burn out over trillions of years until they quietly turn into white dwarfs.
Medium-sized stars, like our Sun, have a more interesting life cycle. The Sun fuses hydrogen into helium in its core through its gravity, releasing extreme amounts of energy that push outwards and stabilize the star. When the Sun is old, the hydrogen in the core is exhausted, and the Sun begins to burn helium into heavier elements. This process results in the loss of more than half of the Sun's mass, forming a planetary nebula. The core of the Sun, now a white dwarf, is extremely dense and has a surface gravity over 100 thousand times higher than Earth.
Life around a white dwarf is very unlikely but possible. Most of them that exist now were former stars that died, probably ruining any planets they once had. However, since they are so small, the planet would need to orbit them about 75 times closer than Earth is to the Sun to have liquid water. This proximity has both advantages and disadvantages. On one hand, it would tightly lock the planet, giving it a permanent day and night. On the other hand, life could be possible at the edges of these day and night zones.
White dwarfs have a very stable energy output, making them potentially safer to live around than many red dwarfs. They are very hot, up to 40 times hotter than our Sun, and are not incredibly active. All the heat inside of them is trapped and has nowhere to go, except on its outer layer. This inefficiency means that white dwarfs will take trillions of years to cool down, which may make them humanity's last refuge.
According to some estimates, white dwarfs might shine as long as 100 billion years, ten billion times longer than the universe has existed so far. After this, no regular stars will shine any more, galaxies will have evaporated, and only then will the first white dwarf turn into the first black dwarf. Black dwarfs will be inactive spheres with no energy left to give, still massive enough to kill you if you get too close, and so cold that they'll be near the coldest possible temperature in the universe. They will be practically invisible, and the universe will enter its last stage: heat death.
1. Humans can survive in the universe as long as they have an energy source.
2. The universe will die, but this will happen slowly over many billions of years.
3. Stars like our Sun will be gone in no time, but there are places that will exist practically forever from a human perspective.
4. The corpses of dead stars, white dwarfs, could be humanity's last home right before the death of the universe.
5. How long stars live varies drastically depending on how massive they are.
6. Really massive stars burn hot and fast, dying violently in supernovae a few million years after birth.
7. 97% of all stars will end their existence as white dwarfs.
8. Small stars, so-called red dwarfs, burn out over trillions of years until they eventually quietly turn into white dwarfs.
9. Medium-sized stars like our Sun are more interesting.
10. The Sun as a huge pressure cooker that fuses hydrogen into helium in its core through its gravity.
11. The fusion of elements releases extreme amounts of energy that pushes outwards and stabilizes the star.
12. When the Sun is old, the hydrogen in the core is exhausted and the Sun will begin to burn helium into heavier elements.
13. More than half of the sun's mass will be lost into space as a spectacular planetary nebula.
14. A white dwarf is born a star corpse.
15. A white dwarf is extremely dense, a teaspoon of white dwarf is about as massive as a car.
16. A white dwarf's surface gravity is over 100 thousand times higher than Earth.
17. Life around a white dwarf is very unlikely but possible.
18. White dwarfs have a very stable energy output.
19. White dwarfs are very very hot up to 40 times hotter than our Sun.
20. White dwarfs might shine as long as 100 billion billion years.
21. The universe will enter its last stage heat death which will leave the universe unrecognizable an absolutely dark and cold graveyard with black holes and black dwarfs scattered over trillions of light-years.
22. If the proton, one of the fundamental parts of atoms, has a limited lifespan, black Dwarfs will slowly evaporate over many trillions of years.
23. If the proton does not decay, black dwarfs will probably turn into spheres of pure iron via quantum tunneling over a timespan so obscenely gigantic that calling it forever is okay.
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