During the day, everything on the earth is nourished by the sun; At night, the sky is not dark, but starry. In the universe, no matter which direction we look, we will eventually see a glimmer of light. But the stars in the universe will eventually go out, leaving only black dwarf (the universe doesn't exist at present) that doesn't emit any visible light. Although darkness will eventually prevail, it will take at least trillions of years.
But the question comes again: do we know there is another one in the universe? A failed star? Brown dwarfs, they also have binary systems, such as Luhman 16, which is about 6 light years away from us, which is a double brown dwarf system. If the orbital decay of double brown dwarfs merges in the future, will it form a red dwarf? If so, there will still be stars in the future universe.
In the future, we will see fewer and fewer stars and galaxies.
Today, we observe the universe with the best equipment available, and it is easy to conclude that in the universe? Does it matter? It seems infinite. Because the longer and farther we look, the more galaxies we see!
No matter which angle we look at in the sky:
In the center of the Milky Way, in the center of nebulae or clusters, outside our Milky Way, and even in a blank area that looks completely empty, we will find a large number of luminous objects. Of course, these luminous objects are either a star, a group of stars or a galaxy or cluster of galaxies.
However, although there are about 400 billion stars in our galaxy and there are at least 200 billion galaxies in the Hubble volume (this is a lower limit), we will see fewer and fewer stars in the future, not more and more.
Why is this happening? There are two reasons, one is the farthest light source, and the other is the nearest light source.
The universe is dominated by dark energy. We have determined that matter is not the main form of energy in our universe through three independent and unrelated measurement methods (cosmic microwave background line, distant type Ia supernova and baryon acoustic oscillation). On the contrary, ordinary matter and dark matter, which make up us, currently account for only one-third of the total energy, and the other two-thirds are a new form of energy, that is, the inherent dark energy of space itself.
About 6 billion years ago, when dark energy dominated the expansion of the universe, galaxies far away from us began to move away from us faster than before. As time goes on, these galaxies are getting farther and farther away from us, and the light they emit today will not reach us at any time in the future, because space expands exponentially under the action of dark energy.
As far as the current situation is concerned, after about 654.38+00 billion years to 654.38+05 billion years, our galaxy groups (Andromeda, Milky Way, Triangle, Magellanic Cloud and about 40 to 50 other dwarf galaxies) will merge into a huge elliptical galaxy in a long time. Because of the existence of dark energy, all other outer galaxies will accelerate away from us, so that we will never see any outer galaxies again. But in our new home, the galactic fairy giant elliptical galaxy? (Milkdromeda) We still have many stars.
But these stars will only exist for a limited time because?
The universe is slowly consuming the fuel of the stars. Now the rate of star formation in the universe is lower than ever: only 3% of the peak value billions of years ago. When the Milky Way and Andromeda galaxy merge, there will be an explosion of star formation (called starburst galaxy), but then the speed of star formation will drop sharply.
Most larger stars will become supernovae, while smaller, sun-like stars will blow away the outer layers of planetary nebulae, while their cores will shrink to form white dwarfs. Over time, these supernovae and planetary nebulae will release a lot of unburned fuels (hydrogen and helium), so new stars will continue to form in trillions of years. However, the speed of star formation should continue to decline, so it is even an extremely rare event to form stars from gas clouds trillions of years from now.
There are many more in the universe? A failed star?
One thing we need to consider is that the star with the smallest mass has the longest life. Real stars and? A failed star? The dividing line between (or brown dwarfs) lies in whether the core can fuse hydrogen into helium, which requires the core temperature to be at least about 4 million degrees Celsius. Its mass needs about 7.5- 8% of the mass of the sun, which represents the dividing line between brown dwarfs and red dwarfs. The lowest quality red dwarf takes about 20 trillion years to consume its own fuel, and its life span is longer than that of any other star. Even the present age of the universe can only be compared with it.
In addition, the fate of red dwarfs is the simplest: red dwarfs do not die of catastrophic supernovae, nor do they blow away their outer layers in planetary nebulae, but can convert their 100% hydrogen into helium, and eventually shrink to form helium white dwarfs.
The most diverse stars in the universe are M-class stars, or red dwarfs, and about three out of every four stars fall into this category. Considering this, and all the stars similar to the sun will become red giants, break away from the outer layer and become carbon-oxygen white dwarfs, we may think that only white dwarfs will be scattered in space after about 100 trillion (1kloc-0/4) years.
Will these white dwarfs last for about 1- 10 trillion years (10 15 or10/6)? White? Until it is cooled down (by Kelvin-Helmholtz mechanism) and no longer emits any band of light, it becomes a black dwarf. At this time, we may think that this is probably the last time we can see any light in the universe. All that remains is darkness.
But in recent years, through the infrared investigation of WISE, we found that besides all the known star types, there are a lot of stars between the gas giant planets and the stars with the lowest mass? A failed star? . If we observe the star system closest to the earth, we will find a brown dwarf binary system! Just as two red low-mass stars can merge into a bluer and higher-mass star, two brown dwarfs below the mass threshold of burning hydrogen can also merge into a real star!
Two brown dwarfs make up Luhman 16.
So the biggest question is, when will they merge, and what other factors may change their fate?
Because gravitational radiation drives orbital decay, it takes about 10 60 to 10 150 years for brown dwarfs of Luhrmann 16 to spiral into each other and merge. It is estimated that the mass of these two celestial bodies is about 4% of the mass of the sun, so when they merge, they will form a real star.
But there are two other things that may change the fate of this special system.
If two stars are completely isolated, they will only spiral close to each other and merge. But stars spend most of their time in galaxies composed of one trillion (or more) stars and star bodies. Sometimes, a star will pass by one (or two) of these brown dwarfs very frequently. Every time it passes, it will have a chance to combine with one of them more closely and kick the other brown dwarf out of the system! Causing stars to escape, that is, fast escape stars.
Of course, this situation is very rare, but as long as there is enough time, even the impossible will happen. The average time scale of such events is about 10 18 years.
Celestial bodies can collide to produce spectacular results! Depending on the collision, the following situations may occur: if two neutron stars collide, black holes and gamma-ray bursts will be produced. If two heavy (carbon-oxygen) white dwarfs collide, a type Ia supernova will occur. If two light (helium) white dwarfs collide, they will ignite helium fusion and produce a red giant. If two brown dwarfs collide, either a more massive brown dwarf or a new M-class red dwarf will be produced. The average event scale of such events is 10 2 1 year.
Therefore, unless the orbits of two brown dwarfs are very close (smaller than the orbit of Mercury to the sun in scale) to avoid the escape of the other, even in the distant future, the two brown dwarfs will not merge.
But as long as brown dwarfs are not expelled, they may collide with other celestial bodies. Considering that there will be collisions and mergers between helium white dwarfs and a large number of brown dwarfs in the universe with the time scale of 10 2 1 year, it is reasonable to assume that even after the last star burns out, we will see occasional and rare new stars in the distant future.