Shulou(Shulou.com)11/24 Report--

It is well known that stars glow and heat mainly through internal nuclear fusion, but in recent years, some scientists have predicted that in the early days of the universe, there may be a class of "stars" that are huge but do not have internal fusion. It is not ordinary matter that provides energy, but dark matter in the body. Because the surface temperature is very low, we can only see that they emit faint light, so scientists call them dark stars.

As mentioned earlier, there are still some problems with today's cosmological models, such as why early galaxies unexpectedly mature, how supermassive black holes formed in a short time, and so on. At present, there are two main directions to solve these problems: one is to patch the specific problems, and the other is to patch the cosmological model from the root. Not long ago, the "doubling of the age of the universe" belongs to the latter, while the "dark star" we are going to talk about today belongs to the former.

As each generation of stars contains a different proportion of metal elements, we currently divide stars into three "generations":

(note: 1. Astronomical "metal" usually refers to elements other than hydrogen and helium; 2. "seniority" here is not a strict alternation of generations, but is used to divide age groups.)

1. Like our sun, it belongs to the latest generation (equivalent to grandchildren). Some of the raw materials have been processed by many generations of stars, so they are rich in metal elements, and this kind of stars are called "first family stars".

2. in a generation older than grandchildren, the key materials only come from supernova explosions of primary stars, so they contain only a small amount of metal elements, which are called "second family stars".

3. The first stars after the Big Bang did not have any metal elements except hydrogen and helium. such stars were called "third star stars" (equivalent to grandfathers).

At present, the first star family star can be seen everywhere, and the second star family star is also occasionally found, but this third star family star has not yet appeared.

In 2007, however, scientists predicted a "star" that was older than the third star of his grandfather's generation. Strictly speaking, this "star" can no longer be called a star, because there is no nuclear fusion, which means that it does not meet the traditional definition of star. But from another perspective, it may be the real first stage of the evolution of stars on a cosmic scale, so I would like to call it "Archaeopteryx".

At the beginning of the Big Bang, when hydrogen and helium were just formed in the universe, the skeleton of matter made up of dark matter was already on the horizon. Soon under the gravitational pull of dark matter, large amounts of hydrogen and helium began to attach to the skeleton like flesh and blood.

Then, in places where dark matter is denser, galaxies begin to form slowly. At the center of the galaxy, because dark matter is denser, large amounts of hydrogen and helium gather here and accumulate more and bigger.

Although the cloud was first triggered by dark matter, with the accumulation of hydrogen and helium, the proportion of ordinary matter becomes larger and larger, until it accounts for more than 99.9% of the gas.

At this time, the mass of the gas mass can reach millions or even tens of millions of suns, and the diameter can reach thousands of astronomical units. At this size, even if Stevenson 2-18, the giant of the star world, comes, he will have to shout "Big Boss".

In terms of mass alone, even the third star of my grandfather's generation is no more than a few hundred times the mass of the sun. For this object, which is millions of times the mass of the sun, it is long overdue to collapse inward and trigger a fusion reaction at the core. But because of the 0.1% dark matter in the body, things began to move in a different direction.

Generally speaking, what dark matter is is still unknown. It may be a thing, or it may be the result of a combination of many things. This time the researchers selected a candidate particle called a "neutral neutrino".

As a hypothetical particle predicted by supersymmetry theory, neutrinos are also called superneutrons. This is a kind of fermion whose charge is zero and the antiparticle is its own fermion, the legendary Mayorana fermion.

For dark matter particles made up of such particles, when the density is high enough, because the antiparticles are themselves, positive and antimatter will have a special annihilation reaction when they meet. The reaction produces corresponding gamma rays and releases special particles such as high-energy electrons. At present, many dark matter detectors, including Wukong, hope to detect dark matter particles indirectly by capturing electrons or gamma rays with special energy spectra.

Then again, the reason why the interior of the cloud, which is a million times the mass of the sun, failed to fuse is that the dark matter particles inside it were annihilated.

The matter of the original cloud should collapse inward under the action of huge gravitation. as the matter continues to collapse inward, the density and pressure of the core of the cloud become high enough and the pressure is strong enough. Nuclear fusion begins to occur between hydrogen atoms under the action of quantum tunneling, so fusion begins.

However, due to the addition of the annihilation reaction, the tendency of matter to collapse inward is suppressed by the energy released by the annihilation reaction. What should have been undertaken by nuclear fusion has now been resisted in advance by the annihilation reaction.

At this time, the cloud shows similar but completely different characteristics from the stars. What is similar to a star is that it can also glow, although this light is not produced by nuclear fusion; the difference is that although it can glow, the light is very weak (relative to its mass of a million times the mass of the sun, of course).

Generally speaking, the larger the mass of a star, the brighter the outside world looks. Like our sun, its surface is about 6000 degrees, while this "star" with a mass of a million times the sun has a surface temperature of only 10000 degrees. The light produced by this temperature is almost invisible to us in the distance, which is the origin of its name "Dark Star".

You see, a dark star is not a "dark matter star" made up entirely of dark matter. Although it does have something to do with dark matter, dark matter only provides a source of energy for such stars.

Due to the energy generated by only 0.1% dark matter annihilation, the temperature of the dark star is very low, so its brightness is not high, but fortunately it is large enough that the overall luminosity is still very high, even reaching the luminosity of 10 billion suns. So, theoretically, as long as we have strong enough infrared detection capability, we still have a chance to find them.

In June 2023, an article published in the Proceedings of the National Academy of Sciences said that researchers had finally identified candidates for three dark stars from hundreds of potentially high redshift objects found by the Weber telescope.

However, at present, the analysis of them is mainly focused on luminosity, and there is no very strong evidence. The researchers will also conduct a detailed analysis of the spectra of the three candidate dark stars to prove whether they conform to the relevant characteristics of the dark star theory.

If a dark star does exist, what problem can it solve?

Because there is very little dark matter in the dark star, as it gradually runs out, the ordinary matter that makes up the dark star continues to collapse inward until it triggers internal nuclear fusion.

This may be good news for dark stars with less mass, because then they can "abandon the dark" and formally become "full" stars. At this point, the universe ushered in the first stars, that is, the third star family.

However, for high-mass dark stars, the situation is not optimistic. With enough mass to make their gravitational collapse unstoppable, the energy provided by nuclear fusion is like a praying mantis, and eventually all matter will collapse into a single point, and a black hole with millions or even tens of millions of times the mass of the sun will be formed.

As the seed of the future supermassive black hole in the center of the galaxy, this dark star-transformed black hole is indeed a solution to form a massive black hole in a short period of time. So there is another possibility to speculate about the origin of supermassive black holes.

This article comes from the official account of Wechat: Linvo says ID:linvo001, author: Linvo

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