Our small earth is not very special on a cosmic scale. This hypothesis is central to the Copernican principle that the earth is not the center of the universe. However, the planet Earth has other strange dimensions. Our host planet, the Sun, is a yellow dwarf star. Since we know most about our star, it is natural to look for the abundance of white and yellow dwarf stars (FGK dwarfs) in other parts of the universe. However, the abundance of these stars in the Milky Way is not great; Because red dwarfs or M dwarfs are the most abundant stars in the Milky Way.
Red dwarfs make up only 75% of all Milky Way stars; Rather, they are colder and live longer than stars like the Sun. The sun is estimated to be 10 billion years old; Red dwarfs are expected to live for trillions of years. However, only 13.6 billion years have passed since the Big Bang; As a result, no red dwarf has reached the end of its life.
Since red dwarfs are abundant and stable, and we do not want to think too much of ourselves, the assumption that our planet is not around red dwarfs is still surprising. However, our star dwarfism is not so common. David KippingColumbia University astronomer discusses the Red Sky paradox in an article. This hypothesis is one of the hypotheses and side effects of the form paradox that shows why we have not yet succeeded in discovering intelligent extraterrestrial life. Kipping writes:
Solving the Red Sky paradox is a guide to targeting distant future life and understanding the limitations of life in the universe.
The artist imagines a planetary system around the red dwarf TRAPPIST-1
Red dwarf stars provide a fascinating landscape for the search for extraterrestrial life. These stars are not as hot as stars like the Sun; As a result, extrasolar planets are closer to each other. This will make it easier to discover and observe these planets.
Astronomers have so far discovered several rocky extrasolar planets such as Earth, Venus and Mars, which are within the life belt of red dwarf stars. Some of these planets are relatively close to their star. Some red dwarf stars appear to host life; For this reason, astronomers are very interested in studying them. In his article, Kipping points out four solutions to the Red Sky paradox.
The first solution: a strange result
The first assumption is that we have a strange position. If the proportions of life around both red and yellow dwarf stars are the same, the Earth would still be distant, and our formation around the sun would be just a one-hundred-percent chance. Thus, a tension arises with the Copernican principle, which shows that there is no superior observer in the world and that everyone has the same position; But the remoteness of the earth indicates that its position is strange. The other three solutions provide a better justification for being subject.
The second solution: life under the red sky
According to Kipping, yellow dwarfs are more viable than red dwarfs and are 100 times less likely to form life around red dwarfs. There is ample theoretical evidence to support this hypothesis. Red dwarfs, for example, have a lot of tongue activity and are turbulent and do not have Jupiter-like planets around them. Kipping adds:
Many theoretical studies rule out the possibility of complex life forming around M or red dwarfs for reasons such as tidal lock and atmospheric collapse and exposure to stellar activity, the small number of Jupiter-like planets, and the original star phase. Accordingly, there are good theoretical reasons for strengthening the second solution; We emphasize, however, that experimental and observational results have not yet been obtained.
The artist’s image of a red dwarf that emits huge tabs
Solution 3: A window to complex life
According to this solution, life does not have enough time to grow around red dwarfs. This seems illogical; But it is related to the pre-main sequence phase of star life; That is, before the start of the hydrogen fuel. At this point, the star is hotter and brighter, lasting nearly a billion years for red dwarf stars. During this time, the greenhouse effect on potential habitable planets occurs; As a result, the chances of complex biodegradation appearing on rocky planets around yellow and white dwarf stars are much higher than for red dwarf stars.
Solution 4: A small number of red worlds
Although about 16 percent of the red dwarfs of rocky planets live in their life belt, these worlds may not be as common as we think. Investigations targeted macro-dwarfs; Because they are brighter and easier to study; But what if there is no habitable planet around them? Low-mass red dwarfs are one of the most abundant examples of the Milky Way; But rocky planets in the life belt of these stars are 100 times less likely than yellow and white dwarfs. Kipping writes:
Intelligent life is the rarest species in the universe and usually grows around the dwarfs M and FGK; But habitable worlds around red dwarf stars are twice as common as FGK stars. Large rankings are two major differences that make these discoveries fascinating; As a result, many Earth-balanced planets known around red dwarfs are uninhabitable, or low-mass red dwarfs are uninhabitable.
A hypothetical image of a habitable world in the red dwarf orbit of Proxima Centauri
The answer may be in all of these solutions, or human beings will reach a definitive answer very soon. With the advancement of technology, especially the better observation of low-mass red dwarf stars and the study of the planets around them, definitive answers can be reached. If we find rocky planets, we can take a closer look at their habitableness and see if they are within the belt of life or affected by stellar processes. Kipping concludes:
Solving the Red Sky paradox will be the focus of astronomical attention and SETI, and show which stars are worth resource allocation. It will also raise fundamental questions about the nature and limitations of life.
The study was published in PNAS.
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