Stars will eventually die. What will happen to the planets around them? There are many different endings.

There are various celestial bodies in the universe, including powerful black holes, neutron stars, and stars that can shine brightly. In addition, there are a large number of planets, dwarf planets, asteroids, and satellites of planets, etc.

The sun is a star that can emit light and heat, and the earth is a planet that orbits the sun. In addition to the earth, there are seven other planets in the solar system. Interestingly, stars are not permanent stars. Instead, planets like the earth have no theoretical lifespan limit. This is a bit problematic. We know that all celestial bodies in the solar system, including the earth, can only operate in an orderly manner under the gravitational force of the sun. As a star, the sun will go out one day. What fate will the planets orbiting it face at that time? In the universe, the mass of stars varies greatly, and stars of different masses will bring different endings to the surrounding planets.

The sun is a yellow dwarf star, and there are many stars in the universe that are much smaller than the sun, which we call red dwarfs.

Because of their small mass, red dwarfs have relatively gentle nuclear fusion and emit relatively low luminosity. However, it is also because of this that red dwarfs have a much longer lifespan than those massive stars. Their theoretical lifespan can reach tens of billions of years, or even hundreds of billions of years. The lifespan of the oldest red dwarf in the universe is equal to the age of the universe. With their gentle constitution, red dwarfs not only prolong their lifespan, but also promise a bright future for the planets around them. After tens of billions of years, when the fuel of a red dwarf is exhausted, it will not perform any dazzling performances, but will slowly and quietly go out.

The extinction of a red dwarf star will not have much impact on the surrounding planets. These planets will continue to orbit around the extinct star, but they will no longer emit any light.

Yellow dwarf stars like the sun will not be content to quietly end. As hydrogen is depleted, hydrogen nuclear fusion weakens, and the outward radiation expansion pressure drops, the internal pressure and temperature of the entire star will rise rapidly, and the fusion of helium will be ignited. From then on, the star will enter the helium nuclear fusion stage from the hydrogen nuclear fusion stage. After that, the nuclear fusion inside the star will continue to advance to heavier elements. As for where it will eventually go, it depends on the mass of the star. For a star like the sun, the internal fusion will probably go to carbon or oxygen. In this process, the volume of the sun will continue to expand and become a red giant.

How much will the volume of the Sun expand?

It will probably just be able to engulf the Earth's orbit, which means that Mercury, Venus and the Earth will eventually merge into the Sun, while the five planets outside the Earth's orbit will be spared. Eventually, the Sun will collapse into a dense white dwarf after nuclear fusion completely stops, and then begin a long cooling process. If time permits, after tens of billions of years, it will eventually cool into a black dwarf. Some of the planets that are not engulfed by it will still accompany it, while others may become wandering planets due to changes in gravity. If a star's mass is more than 8 times and less than 30 times that of the Sun, then it will have an extremely splendid ending, because its internal nuclear fusion will be pushed all the way to iron.

Iron is the last hurdle that stellar fusion can reach, because the fusion of iron will change from releasing energy to absorbing energy.

So at this moment, the outward radiation expansion pressure generated by stellar fusion will completely disappear, and the entire star will collapse rapidly toward the center. When it reaches a certain threshold, it will rebound, and then a huge amount of energy will be released in an instant, and a very wide area of ​​the universe will be lit up. This process is called a "supernova explosion." After the explosion, it will collapse into a neutron star. A supernova explosion is an extremely violent celestial activity. Not only will the planets orbiting this star be destroyed by this energy, but even the ecological environment of a planet 50 light years away will be destroyed by the impact of this energy.

If a star's mass exceeds 30 times that of the Sun, the situation becomes somewhat different.

Its fusion activity will also proceed to the iron element, and then a supernova explosion will occur, but the final product is not a neutron star, but a black hole. Black holes are the most powerful celestial bodies known in the universe, and they will attract and devour all the matter around them. Therefore, the stars around this star will first be swallowed up during the expansion of the star, and those that are not swallowed will be destroyed during the supernova explosion, and the residues after the destruction will eventually return to the black hole. When there is no more matter around the black hole to devour, the accretion disk around the black hole will lose its light, and the black hole will become a completely invisible celestial body, because the escape velocity within the black hole's event horizon exceeds the speed of light.

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