Is there another Earth in the vastness of the universe, and is there life on it? This is what mankind has been dreaming and exploring all along. With the development of astronomical technology, we have discovered thousands of exoplanets, some of which are located within the habitable zone of their stars, that is, their temperatures are suitable for the presence of liquid water, which is considered one of the necessary conditions for life. One of the most striking planets is Gliese 581g, which is known as the "super-Earth" and is one of the most likely planets known to host life.
In the direction of the constellation Libra, there is a red dwarf star named Gliese 581. Around it, there is a planetary system with six planets in it. One of them, called Gliese 581g, was announced on September 29, 2010 by astronomers in the United States.
This is the result of 11 years of observation at the Keck Observatory in Hawaii by observing the oscillation of the stars. The size and mass of Gliese 581g are slightly larger than that of Earth, about 13 times and 37 times. Its surface is made of rock, possibly an atmosphere and water.
The special feature of Gliese 581g is that it is in the habitable zone of the star, that is, its temperature allows liquid water to exist. Liquid water, on the other hand, is considered one of the necessary conditions for life. The average surface temperature of Gliese 581g is between -31 and -12 degrees Celsius, but if there is an atmosphere, the greenhouse effect may make some places a little warmer.
However, the living environment of Gliese 581g is not so easy to adapt to. Because it is so close to the star, it has a short orbital period of only 37 days. Moreover, its rotation period, like its revolution period, is also 37 days. This means that one side of it, forever facing the star, receives light and heat; And the other side, forever facing away from the stars, is in the dark and cold. Such a situation can lead to a very severe temperature difference between day and night and a very severe storm. On the light side, water and atmosphere may evaporate; On the dark side, water and atmosphere can freeze. And from the hot side to the cold side, there will be a strong wind blowing through, forming a huge storm. Therefore, if there is life, it may only live at the junction of day and night, that is, on the circle of morning and dusk, where the temperature is relatively moderate, and there may be liquid water.
The specifics of the surface and atmosphere of Gliese 581g, we don't know much yet, because we haven't seen it directly. We can only guess based on theoretical models and similar examples. Since Gliese 581g is a bit heavier than Earth, it also has a bit more gravity than Earth, which could mean that it has a thicker atmosphere and may also have more greenhouse gases, such as carbon dioxide and water vapor. These greenhouse gases may make the surface temperature of Gliese 581g warmer, and may also make the radiation of the star more uniform. However, Gliese's 581g star is a red dwarf star, its brightness and temperature are lower than that of the sun, and the light it emits is more infrared than visible. This may mean that the light intensity on Gliese 581g is a little weaker than on Earth, and it may also affect the photosynthesis of plants.
As a result, life on Gliese 581g, if present, may have a different color and shape than Earth. As for the presence of water on Gliese 581g, it depends on its initial water content, as well as the circulation of water on both sides of the day and night. If water is able to maintain a balance between day and night, then there may be water on Gliese 581g, and possibly even oceans and clouds. If the water is trapped on the side of the eternal night, forming an ice cap, then there may be no water on the Gliese 581g, or only a small amount of water.
The definition and conditions of life are a complex and controversial issue, and in general, life can be defined as an organism capable of self-sustaining, self-replication, and self-evolution, which requires some basic conditions such as energy, matter, liquid medium, and stable environment.
Energy is the driving force of life, and it can come from the radiation of stars or from the heat of the planet's interior; Matter is the basis of life, it can be carbon, silicon or other elements, but it must be able to form complex molecules and structures; The liquid medium is the carrier of life, it can be all liquid, but it must be able to dissolve and transport matter and energy;
Based on these conditions, we can assess whether Gliese 581g has the likelihood of life. First of all, Gliese 581g has enough energy**, it can come from the radiation of the star, or from the core of the planet or tidal heating in the interior of the planet; Secondly, Gliese 581g has enough substance**, which can come from the rock composition of the planet, or from the planet's atmosphere or water cycle; Thirdly, it is possible that Gliese 581g has the presence of a liquid medium, which is most likely water, but also other liquids, such as methane or ethane; Finally, it is possible that Gliese 581g has a stable environment, which is most likely a dawn and dusk circle at the junction of day and night, or it may be the planet's subsurface or ocean.
To sum up, Gliese 581g has the basic conditions for life, that is, it is possible for it to have life, or at least to give birth to life.
Why scientists think Gliese581gThe likelihood of life on the existence is highThis?
First, Gliese 581g is located in the habitable zone of the star, which is one of the most basic conditions for the existence of life. The habitable zone refers to an area around a star that is at a temperature suitable for the presence of liquid water, which is considered one of the necessary conditions for life. If a planet is too close to a star, its surface temperature will be too high and the water will evaporate or decompose; If a planet is too far away from a star, its surface temperature will be too low and the water will freeze or condense. Only within the habitable zone can a planet maintain the existence of liquid water, and thus the existence of life. Gliese 581g is one such planet, with an average surface temperature between minus 31 and minus 12 degrees Celsius, but due to the greenhouse effect of the atmosphere, there may be warmer areas, such as the dawn and dusk circle at the junction of day and night, where temperatures may be suitable for the presence of liquid water, and there may also be oceans and clouds.
Second, the size and mass of Gliese 581g is suitable for the existence of life, which is another important condition for the existence of life. The size and mass of a planet determine its gravity and density, which affects its atmosphere and surface. Gliese 581g has a diameter of about 1 of the Earth3 times, with a mass of about 3 times that of the Earth7 times, the surface is made up of rocks, there may be an atmosphere and water. Its gravity is strong enough to hold the atmosphere, but also enough to hold water and other substances, without compressing them too much.
Thirdly, the energy of Gliese 581g is sufficient, which is another key condition for the existence of life. Energy is the driving force of life, and it can come from the radiation of stars or from the heat of the planet's interior; If a planet does not have enough energy**, its surface temperature will be too low and water and other substances will freeze or condense; If a planet has too much energy**, its surface temperature will be too high and water and other materials will evaporate or decompose.
Fourth, it is only with moderate energy** that it is possible for a planet to maintain a temperature and chemical equilibrium suitable for life. Gliese 581g has two main energies**, one is radiation from the star, and the other is heat from the planet's interior. Since its rotation is locked by the star, one side of it is always facing away from the star and the other side is always facing away from the star, which means that one side of it receives radiation from the star and the other side does not. This radiation distribution creates a temperature difference between day and night, creating a cycle of wind and water, that is, water and atmosphere on the hot side will flow to the cold side, and water and atmosphere on the cold side will flow to the hot side. This cycle can help disperse the radiation from the stars, making the temperature more evenly distributed, and can also help transport matter and energy to provide the resources needed for life. On the other hand, since Gliese 581g has a larger mass than Earth, it may also have more internal heat than Earth, which may come from the planet's core or tidal heating.
Fifth, this internal heat can provide the planet with another type of energy**, or it can provide the planet with the possibility of another life form, such as life in the ground or in the ocean.
Sixth, the material abundance of Gliese 581g is the last necessary condition for the existence of life. Matter is the basis of life, it can be carbon, silicon or other elements, but it must be able to form complex molecules and structures; If a planet doesn't have enough matter**, its surface chemistry will be too monotonous to support the diversity and complexity of life; If a planet has too much material**, its surface chemistry will be too chaotic to support the stability and harmony of life. Only with the right amount of matter** is it possible for a planet to form molecules and structures suitable for life.
Our knowledge of Gliese 581G is still very limited, and we are not yet sure of its composition, temperature, chemistry, biology, etc. We also don't know if it really has life, and the forms and characteristics of life. But what we can be sure of is that Gliese 581g is a planet that makes us curious and yearning for life and the universe. It makes us imagine what kind of sights we would see, what kind of life we would meet, what kind of communication we would have if one day, we would be able to get there.