The universe is slowly dying, but humans can survive as long as we have an energy source. The universe's death will happen slowly over 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, such as the corpses of dead stars, or white dwarfs. These could potentially be humanity's last home before the death of the universe.
Stars live for varying periods depending on their mass. Massive stars burn hot and fast, dying violently in supernovae a few million years after birth. However, the majority of stars (97%) will end their existence as white dwarfs. These can be divided into two categories: small stars, or red dwarfs, which 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, as a huge pressure cooker, fuses hydrogen into helium in its core through its gravity. When the Sun is old, the hydrogen in the core is exhausted, and the Sun will begin to burn helium into heavier elements. This process will shed its outer layers, leaving behind a white dwarf. A white dwarf is extremely dense, with a surface gravity over 100 thousand times higher than Earth. Life around a white dwarf is very unlikely but possible.
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 rank among the hottest objects in the universe. The heat inside them is trapped and can only escape into space through radiation. This makes them very long-lasting, potentially shining as long as 100 billion years.
In the end, the universe will enter its last stage, heat death, leaving it unrecognizable as an absolutely dark and cold graveyard with black holes and black dwarfs scattered over trillions of light-years. The fate of black dwarfs is uncertain. If the proton, a fundamental part of atoms, has a limited lifespan, black dwarfs will slowly evaporate over many trillions of years. If the proton does not decay, black dwarfs will probably turn into spheres of pure iron via quantum tunneling over an obscenely gigantic timespan. These ions will then travel completely alone through a dark universe, where nothing new will happen anymore.
Here are the key facts extracted from the text:
1. Humans can survive in the universe as long as they have an energy source.
2. The universe will eventually die, but it will happen slowly over many billions of years.
3. Stars like the Sun will be gone in a relatively short time on a universal time scale.
4. White dwarfs, the corpses of dead stars, could be humanity's last home before the death of the universe.
5. The lifespan of stars varies drastically depending on their mass.
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, or red dwarfs, burn out over trillions of years and eventually turn into white dwarfs.
9. Medium-sized stars like the Sun will shed their outer layers and leave behind a white dwarf.
10. A white dwarf is about the size of Earth but has about half of the mass of its former self.
11. White dwarfs are extremely dense, with a teaspoon of white dwarf being as massive as a car.
12. The surface gravity of a white dwarf is over 100,000 times higher than Earth's.
13. Life around a white dwarf is very unlikely, but possible.
14. Planets would need to orbit white dwarfs about 75 times closer than Earth is to the Sun to have liquid water.
15. White dwarfs have a very stable energy output, making them potentially safer to live around than red dwarfs.
16. White dwarfs are very hot, up to 40 times hotter than the Sun.
17. The heat inside white dwarfs is trapped and can only escape through radiation.
18. White dwarfs will take trillions of years to cool down.
19. According to some estimates, white dwarfs might shine for up to 100 billion billion years.
20. Black dwarfs, the remnants of white dwarfs, will be inactive spheres with no energy left to give.
21. Black dwarfs will be near the coldest possible temperature in the universe and will be practically invisible.
22. The universe will eventually enter a state of heat death, leaving it unrecognizable and dark.
23. Black dwarfs may slowly evaporate over trillions of years if the proton has a limited lifespan.
24. If the proton does not decay, black dwarfs may turn into spheres of pure iron via quantum tunneling.