Looking for exoplanets suitable for human habitation

In any case, if we want to find an exoplanet that is as suitable for human survival as the earth, we must compare it with the ecological environment of the earth. Water is the foundation of life, so there must be water suitable for human habitation on the planet. To meet this condition, the planet must be in the livable zone of the star. If you get too close to the star, the water will be evaporated, and the planet will become a desert without retaining water. This is the status quo of Venus. Venus is similar in size and mass to the earth, but it is too close to the sun, and its surface temperature is as high as 500℃, so basically no life can survive on its surface.

If you are too far away from the star, the planet will become too cold. Water can only exist on the surface in the form of ice, and there may be liquid water deep underground. Neptune is an example. In addition, the planet must be solid, have a surface that can support life activities, and contain an atmosphere that protects life from the radiation of stars, while providing breathing air for living things.

Our Milky Way alone has 1000 billion stars, and there may be a planet near each star. Some of these planets may be located in the livable zone and have all the basic substances of life. From the known 4500 exoplanets, we have carefully selected and identified 24 super livable planets, which are more suitable for the existence and evolution of life than the earth, and can be called the paradise of life.

This super livable planet must be twice the mass of the earth and at least 1.3 times the volume of the earth. Greater mass and volume means stronger gravity, denser and warmer atmosphere, which will ensure the diversity of life on earth, the so-called super earth.

In addition, the star surrounded by these super livable planets should be an ideal star, smaller than the sun, with a life span of at least150-30 billion years. In contrast, the life span of the sun is less than 65.438+0 billion years, and it took about 4 billion years for complex life forms to be born from the earth. Therefore, the ideal star should have a long life, so that it can continue to provide energy after the exoplanets evolve life forms.

Red dwarfs are a good choice. It is smaller and less bright than the sun, but its life span can be between 20 billion and 70 billion years, which will give living things enough time to develop and evolve. The climate conditions of super livable planets will also be different. The average temperature should be 18, which is higher than the earth's 15. Proper temperature will ensure that more water exists in the form of clouds, liquids and moisture. At this temperature, it is most conducive to the development of biodiversity. The whole planet looks like a tropical forest on earth.

With the emergence of a new generation of telescopes, we may find out whether these livable exoplanets have life. If these 24 livable planets are suitable for life, then the following planets will be their typical representatives.

GJ 273b, an exoplanet revolving around GJ 273. GJ 273, also known as Rutan Star, is a red dwarf star located in Canis minor, about 12 light-years away from the solar system. Generally speaking, red dwarfs periodically burst into flares, blowing away the atmosphere of the planets in their orbits. However, GJ 273 is relatively calm. So far, no flare explosion has been observed. GJ 273b is located in the livable zone of Rutan, and its mass is about three times that of the earth. It takes about 18.6 days for it to orbit the star once, which means that the year of GJ 273b is less than three weeks on earth.

In 20 17, an astronomical organization named "METI" used a 32-meter-caliber radio telescope in Norway to send signals to GJ 273 solar system three times in a row, including 33 short music works, some mathematical and scientific achievements, and the position of the solar system and the earth in the Milky Way. If intelligent life does exist in GJ 273 galaxy, we will receive a reply in 2042. However, it is unwise to disclose the location of the earth voluntarily. If there is an evil alien creature 12 light years, and the technology is far superior to human beings, it will be a disaster for mankind.

Kepler-1638B is the farthest exoplanet from the earth where life may exist. It is about 3000 light years away from us, located in the direction of Cygnus, and rotates around the star Kepler-1638, which is in the livable zone of the star system. Its similarity index with the earth reaches 80%, its volume is twice that of the earth, and its mass is four times that of the earth. It has rocks and liquid water on its surface, which is very similar to the surface environment of the earth. It takes 260 days for it to revolve around its main star, which makes it possible for the planet to have four seasons similar to that of the earth. Kepler-1638B is similar to the earth in all aspects. If there is humanoid life, this super earth will accommodate 20 billion people, but because it is too far away, even heaven, we may miss it forever.

Kepler 452b is located in a star system similar to the solar system, and rotates around Kepler 452, the main star. It takes about 385 days to make a revolution. Kepler 452 star system is located in Cygnus, which is 1402 light years away from the Earth. Kepler 452 is only 500 million years older than the sun. It is in the prime of life and can provide enough energy for life. The mass of Kepler 452b is five times that of the earth, about 1.8 times that of the earth, and its surface gravity is twice that of the earth, which means that you may not be able to jump with all your strength on this planet. Kepler 452b has a history of 6.5 billion years, 2 billion years older than the earth's history of 4.5 billion years. Maybe the water on its surface has evaporated for a long time.

Generally speaking, Kepler 452b is as similar as 90% to the earth, contains atmosphere and moisture, is in a suitable livable zone, and even is extremely similar to the earth for one year, which can be regarded as version 2.0 of the earth. However, due to the dividing line between mini Neptune (an exoplanet similar to Neptune, the surface of the planet is the atmosphere, and below it is the ocean formed by highly volatile substances such as water and ammonia) and super-Earth, only a planet twice the size of radius of the earth can be a rocky planet, while Kepler 452b is only 1.8 times that of radius of the earth, so it may also be a marine planet.

Gliese 58 1g, about 20 light years away from the earth, revolves around the red dwarf Gliese, and is the sixth planet in Gliese galaxy, located in the direction of Libra. The existence of gliese 58 1g has been controversial in the scientific community. According to the observation data of British Observatory, there are only five planets in the livable zone of gliese galaxy, but gliese 58 1g does not exist. Some astronomers also pointed out that no credible signals from the planets were received in the livable zone of the gliese galaxy; However, the observation data of the American Observatory show that the probability of gliese 58 1g is 99.9978%.

If gliese 58 1g does exist, it will be the most similar exoplanet to Earth. The mass of gliese is about four times that of the Earth, and its volume is 65438+ 0.4 times that of the Earth. Its period of revolution is 37 days. Gliese 58 1g is the host star tidal locking, which means that only one side of Gliese is facing the host star, and the other side is always facing away from the host star. There is no diurnal variation on gliese 58 1g, and the temperature on the eternal day will reach a timely degree Celsius, while the temperature on the eternal night will be as low as minus 200 degrees Celsius. If there is life on this planet, the terminator line will be the most suitable place for living things.

These 24 planets are all located in the livable zone of their main stars. Theoretically, we can immigrate there and start our future life. But they are too far away from us. Even if modern rockets can fly at five times the speed of sound, it will take 654.38 million+years to fly out of the solar system, let alone reach these distant galaxies. Therefore, until we master the technology of interstellar travel, we can only stay on the earth honestly. As for interstellar migration, it is still in the stage of science fiction. However, exploring these exoplanets will help us to improve our understanding of extraterrestrial life and how it formed.