Earth may not be unique, and as the exploration of the universe gets further and further away, the pace of exploration becomes faster and faster. It is not impossible to find a planet with more mass and better habitation than Earth.
What kind of planet can inspire the human desire to explore and is expected to become the habitat for human escape before the destruction of the world? This kind of planet is called "Super Earth".
What is the definition of a super Earth? Scientists have discovered a super-Earth. Since it is very similar to Earth, does it have the right conditions for human habitation? Besides this discovered planet, what other planets are similar to Earth? The super-Earth that scientists have observed so far is 22 light-years away from the Earth and is considered the twin of the Earth, with a similarity of 84%.
Defining Super Earth
Astronomers call planets that are similar to Earth, but more massive than it, super-Earths. In technical terms, such planets are called super-Earth-like planets, with the word "Earth" referring to the Earth. Super-Earths are thought to have undergone the same plate tectonic evolution as Earth, forming canyons and mountains, being impacted by extraterrestrial "meteorites", and being subject to volcanic eruptions caused by the movement of material in their cores.
In the earliest days, scientists defined super-Earths by focusing only on their mass and using it as the only criterion for judgment. Nothing was mentioned about the availability of suitable temperature and humidity, major substances, orbital parameters, and habitable environment. Later scientists reflected that the presence of ideal atmospheric conditions should be added to the definition of a super-Earth, followed by the concept of having a solid surface.
In retrospect, first of all Super Earth is similar to our Earth. Our Earth is overwhelmingly rocky, except for its atmosphere. Depending on the type of rock, it can be divided into silicate planets, where silica compounds dominate, and carbon planets, where carbon compounds dominate. So far, more than 4,000 super-Earths have been discovered in the space of the universe that can be observed, and they seem to be concentrated in a habitable zone of the Milky Way.
This habitable zone is located between the center of the Milky Way and the edge of the galaxy. The center of the galaxy is dense with stars and active black holes, not exactly the place for habitable planets. The edge of the galaxy is a number of fringe galaxies that are gradually moving out of the galaxy, lacking light and heat, and not the place for normal planet production.
In this habitable zone, there exist habitable solid planets with suitable atmospheres to wrap the planets, reduce space radiation, prevent direct solar UV radiation to the surface, and reduce evaporation of liquid water. Speaking of liquid water, the right temperature is needed. Too cold would be like Uranus which is an icy planet, too hot would be like Venus which is covered with the greenhouse gas carbon dioxide. Keep in mind that Venus has a surface temperature of 472°C at its hottest.
One super-Earth located in the habitable zone, 22 light-years from Earth, is the most likely candidate for future human space migration, located in the Gliese 667C star system of the Scorpius III star system.
Gliese 667C stellar system
The Gliese 667C star system is only one-third the size of the Sun's star system, and is also fainter and cooler than the Sun. In the midst of the glowing star system, Gliese 667C looks so insignificant. However, the temperature of the Gliese 667C star system is still slightly higher than that of the Earth, and if we humans come to this star system, it will provide a more extensive living space than the Earth, and it is likely to be much richer in resources than the Earth.
Scientists have explored the Gliese 667C stellar system in more detail to see if there is extraterrestrial life in the system. Just like the Sun, the solar system is formed with the Sun at its core. Gliese also has many planets orbiting it. There are seven low-mass planets in close orbit around Gliese 667C, and based on further exploration of these seven low-mass stars, scientists have found at least five signals that life may exist in some of the low-mass stars in the Gliese system.
Learn more about these 7 planets orbiting Gliese 667C. Three of these rocky planets are very habitable, and one of these three, called "Gliese 667Cc", is the most beautiful planet in the Gliese 667C system. Here we call it G667Cc for short.
G667Cc has only about 28 Earth days in a year, which is less than a month on Earth, so spending time on G667Cc will feel like years and months. The surface temperature of G667Cc is higher than that of Earth, and it is closer to the "hot" edge of the Gliese galaxy's habitable zone.
Suitable light and heat shape a livable living environment. Since G667Cc has a high 84% similarity to Earth, we can assume that it has some conditions suitable for human habitation, so what are they?
G667Cc's livable conditions
The light-heat conditions and mass of the Gliese 667C star system are smaller than those of the Sun, so the light-heat received by G667Cc from the star, and the gravitational effect on it, are no more than those of the Earth. If the Sun gives the Earth 100% of its luminous heat, G667Cc receives about 90% of its luminous heat converted to energy.
Being in the habitable zone of the Gliese 667C stellar system is a lucky thing for G667Cc. It has the right temperature, so there is a high probability that liquid water is present. The presence of water means that there may be a gestation of life. We know that life cannot be born without water, carbon and oxygen, and the current conditions have one of them, so does it have the basis to produce oxygen and emerge carbon based organisms?
But G667Cc is not so perfect. Because its light is not well "filtered", some of it is infrared, which is still lethal to the ground and to any living creatures that may be present. We can't go to this planet, which is 22 light years away from Earth, to detect the presence of liquid water, but we can only use astronomical telescopes to know its distance and observe its approximate shape.
For the star Gliese G667C, the production of flares and intense energetic charged particles can also affect the environment of G667Cc. Perhaps over time, its similarity to Earth will diminish, becoming less Earth-like and less likely to be habitable for humans.
Our observations of Gliese 667C and G667Cc continue, as well as attempts to discover and observe second and third super-Earths. What other planets similar to Earth have been discovered through space radio telescopes and the "eye in the sky"?
More Super Earths Discovered
Like G667Cc, G832C, which belongs to the parent star system Gliese 667C and is 16 light-years away from Earth, is also a super-Earth similar to Earth. Because its distance from Gliese 667C is closer than the Earth-Sun distance, G832C receives energy radiation from its parent star Gliese 667C that is close to the magnitude of solar radiation received by Earth.
The mass of G832C is more than five times that of the Earth, and although its average temperature is only -20 degrees, the thick atmosphere provides better insulation, making the body surface temperature of G832C higher than this value.
There is another super-Earth with 99% similarity to Earth that must be mentioned: Kepler 452b in the constellation Cygnus, 1400 light-years away from Earth. Kepler 452b is an Earth-like planet discovered by NASA, with a diameter 1.6 times that of Earth. The key is its rotation period, which is only 20 days different from Earth's 365 days.
Kepler 452b is probably the closest "twin planet" to Earth ever discovered, located in the habitable zone of its parent star system and with an orbital period similar to that of Earth. However, just when it is thought that Kepler 452b is likely to produce liquid water and develop living matter, there is bad news from scientists.
Kepler 452b is not a cousin of the Earth, and compared to the Earth, it is older. Earth's lifespan is 4.5 billion years, Kepler's is 6 billion years, in fact both Earth and Kepler 452b are old planets.
Scientists say Kepler 452b is aging at a faster rate than Earth, and has even entered the aging phase. By the time we are lucky enough to reach Kepler 452b, which is 1,400 light-years away from Earth, perhaps it will have long since been destroyed and ceased to exist. Unless we can achieve wormhole traversal and open a free-passing free gate between Earth and Kepler, obviously, this is a pipe dream.
Searching for every possible Earth
Whether it is G667Cc and G832C in the Gliese 667 galaxy, or Kepler 452b, which is in decline and may disappear someday, these discoveries are all human efforts to find the next habitable planet.
In fact, the sun is slowly aging as well. Perhaps one day we will need to take the Earth to escape from the solar system, as "Wandering Earth" plays out, but that is a long way off, something that future generations may only worry about.