What are the only celestial objects "white dwarfs" and "black dwarfs" left when the universe is about to end?

Creatures, including mankind, can continue to live by the existence of an energy source that is the source of activities. In the solar system where we live, the sun plays its part, but from an astronomical point of view the sun burns out and it will die. When a star like the sun burns out, sometimes a supernova explosion is caused by the size of the star, many of them advance to the stage of "white dwarfs" and further gradually cool down to become "black dwarfs", and at the end The dark and cold universe will come. The final appearance of such a universe,Kurzgesagt - In a NutshellIt is summarized in a movie.

The Last Light Before Eternal Darkness - White Dwarfs & Black Dwarfs - YouTube


How long is the life of the star? The answer is that it varies from star to star.


And it is determined by the mass of the whole star.


For example, a gigantic and burning star will die from a supernova explosion in a short time of several million years from the birth.


But this is an exception to the last. 97% of the stars are finallyWhite dwarf starBecome it and close that lifetime.


It is thought that there are two ways to reach there. One isRed dwarfA star with a mass smaller than the sun is slowly burned out, and finally it reaches a white dwarf. However, it is thought that it will take several tens of milliseconds to several trillion years to reach it, and it is believed that there is no red dwarf that has reached a white dwarf in the present universe.


Interesting is the case of a star with the same mass as our sun.


Inside the stars like the sun, due to the high pressure and high temperature due to gravity, there is a continuous process in which hydrogen atoms undergo nuclear fusion reactions and turn into helium. At this time, high energy is released and a force going to the outside is born, but surrounding substances suppress their power, so that the sun does not explode and maintains internal pressure and temperature and stably reacts with nuclear fusion reaction It is in a condition to happen.


When such a sun gets older, the core's hydrogen, which was fuel, is exhausted, and now a reaction to change helium to a heavier element starts to occur.


Then the sun will release the material around the core as a gas into space. The star which became this statePlanetary nebulaThe released gas spreads over millions of kilometers and the state of being illuminated by ultraviolet rays emitted from the stars will also be observed from the Earth.


And what remains in the center is a white dwarf, which can also be called "a dead body of a star".


Although its size is considered to be about the same as that of the Earth, its mass is in a state so large as not to be compared with the Earth.


If you say that roughly half the mass of the original star has been condensed to the same size as the Earth, you can somehow imagine that it is in a tremendous compressed state.


It is impossible in reality, but if you scoop a body of white dwarfs with a spoonful, it is considered that the weight is equivalent to one car.


Because of the extremely high density, the surface gravity of the white dwarfs is expected to reach 100 times that of the Earth.


If you get down on a white dwarf, you will not be able to endure your weight immediately and will be in a state of peppers. Because "100 G" power on the planet is applied to the body.


A planet should exist around the white dwarfs that were former stars. If so, is it possible for life to exist in a star system centered on white dwarfs? The answer is "It is very difficult but possible".


First of all, since the star should have damaged the surrounding planet by the stage until it reaches the white dwarf, it can be said that it is difficult to keep life in existence until then.


Also, because the white dwarf itself is very small, the planet can not enter a habitable zone suitable for the presence of water unless it orbits the near distance of 1/75 of the distance between the present Earth and the sun .


It is said that there are both good and bad aspects in this proximity. One thing that catches the planet is that the same side always faces the white dwarfs.


Therefore, the face facing the white dwarf becomes very hot and the opposite face is extremely cold and cold. Only a narrow area on the boundary between these two faces is the place where life can exist.


On the other hand, white dwarfs are celestial bodies whose energy release is very stable.


Therefore, there is the merit that it will not be exposed to the harsh environment like a red dwarf.


These are still the stages of the theory that does not go beyond speculation. But in the future, if a white dwarf and a planet that revolves around the surroundings with good conditions are discovered, humanity may be able to find stars that can settle for millions of years ahead.


So why can white dwarfs continue to shine for quite a long time compared to other celestial bodies?


That is because white dwarfs are very hot. It is believed that its temperature is 40 times as hot as the sun, and is considered to be the highest temperature object in the universe. However, the source of that temperature is not due to active reaction such as nuclear fusion, but it just gets cold.


Since high temperature energy is confined in a small celestial body and its energy is only radiated from space with a relatively small surface area to outer space, it will take 100 billion years before the white dwarfs cool down It is calculated.


Therefore, if humanity is present when hundreds of millions of years later, white dwarfs are considered to be a slightly left energy source in the dying universe.


In one passage, white dwarfs are thought to continue to shine for 100 billion times as much as 100 billion years. This is thought to be 10 billion times the lifespan of the universe itself, and there is also a view that only the white dwarfs are shining to the end in the universe.


And then, the appearance of the end of a white dwarf that does not exist in the present universe,Black dwarfIt is supposed to be born. This is the stage at which all energy that the white dwarfs had had been released and could not emit light or heat anymore. In this way, creatures can not gain the energy to keep their lives, and the last hope of connecting life will be cut off.


However, even in such a state, it is a celestial body with massive mass and gravity, so there is no difference that it is a dangerous existence that deprives life only by approaching it.


Also, as energy is exhausted, the celestial bodies that are the hottest in the universe are also thought to be the coldest celestial body in the universe. By the time the white dwarf gets cold, the other celestial bodies have finished their entire lives in the universe, and the universeThermal deathWe enter the final stage called.


The universe that has undergone thermal death is completely dark and cold world. It is said that it will be the world of death where only black holes and black dwarfs exist at a distance of several hundred billion light years.


Nobody knows exactly how black dwarfs will last. If the lifetime of the protons constituting the atoms is limited, the black dwarfs are expected to gradually collapse gradually over the next several trillion years.


Conversely, if the proton does not collapse, black dwarfs take a long timeQuantum tunnelIt is thought that composition changes by proton movement as a result of the result, and ultimately changes to a pure iron celestial body.


Later, this object will not shine again, and will continue to wander through the dark universe that has cooled down forever.


But these things happen a matter of many trillion years from now, it is not something people should worry about right now.


We now live in the age when the universe is full of stars, light, energy.


And perhaps there may be enough time to reach those stars.