There are tens of billions of "super earths" in , galaxy, , which are more common than the earth we live in now and are more suitable for human habitation.
Astronomers often discover planets orbiting stars outside the solar system and call them " exoplanet ". In the summer of 2022, NASA's team of transiting exoplanet survey satellites discovered several particularly interesting exoplanets that operate in the habitable zone of their parent star.
One of the planets has a volume of 30% larger than the Earth, and the orbital period around the star is less than three days. Another planet is 70% larger than Earth and may have deep seas on the surface. These two exoplanets belong to the super earth. They are larger in size than the Earth, but smaller than giant planets such as Uranus and Neptune .
Earth is still the only place where life exists in the known universe, so it seems to be a logical choice to focus on Earth-like planets. Research shows that astronomers' biggest possible goal of discovering life on other planets is super Earth.
Most super-earths orbit cold dwarf , which has a lower mass and a much longer lifespan than the sun. Scientists have discovered that the super-Earth orbits 40% of the cold dwarfs they have observed. According to this calculation, astronomers estimate that in the Milky Way alone, there are tens of billions of super-earths in the habitable zone, and that liquid water may exist on them. Since all life on Earth needs water, water is considered a key factor in a habitable planet.
According to current predictions, about one-third of exoplanets are super-earth, making them the most common exoplanet type in the Milky Way. The nearest exoplanet is only 6 light years away from Earth. From this we can see that our solar system looks so unusual because it does not have a super Earth with a mass between Earth and Neptune.
Another reason why super earths are the ideal goal of finding life is that they are easier to discover and study than planets of the size of Earth. Astronomers use two methods to detect exoplanets. One is the gravitational effect of a planet on its parent star, and the other is that the star's light will briefly dim when it passes in front of the parent star. Both methods of detection are easier for larger planets.
Modern astrobiologists are exploring why planets are suitable for life to survive. It turns out that the earth is not the best of all worlds where life is possible. For most of the 4.5 billion years of history, the Earth was not suitable for humans and other larger creatures to live in. Simulations show that the long-term livability of the earth is not inevitable, but there is a great chance. It can even be said that it is so lucky for humans to be alive.
researchers have listed a range of attributes that make planets very suitable for life. Larger planets have higher geological activity, and scientists believe this trait will promote biological evolution. Therefore, the most habitable planet has a mass of about twice that of Earth and is 20% to 30% larger than Earth. It will also have a sea shallow enough that light can shine on life on the seabed, with an average temperature of 25 degrees Celsius.
In addition, it will have a thicker atmosphere than the earth to function as an "insulating blanket". Finally, such a planet will orbit older stars than the Sun to allow life to develop longer, and it will have a magnetic field strong enough to withstand cosmic radiation. Scientists believe that combining these properties will make a planet super habitable.
According to this definition, super earth has many attributes of super habitable planets. So far, astronomers have discovered 24 super-Earth exoplanets that, if not the best of all possible worlds, are theoretically more human-friendly than Earth.
Recently, another exciting new discovery has been added to the list of habitable planets. Astronomers have begun to discover exoplanets thrown from star system , which may have billions of such planets roaming the Milky Way. If a super-earth ejected from its star system, with dense atmosphere and water, it could sustain life for tens of billions of years, far longer than the time life on Earth could last before the sun died.
To detect life on distant exoplanets, astronomers will look for biometric features that can be detected in the planet’s atmosphere, i.e., by-products of biology.
NASA's James Webb Space Telescope was designed before astronomers discovered exoplanets, so the telescope was not optimized for exoplanet research. But it is able to do some of this scientific work and plans to target two super-earths that may be suitable for human habitation in the first year of its operation. Another group of super-earths with huge oceans discovered in the past few years, as well as planets discovered this summer, are also targets for the James Webber telescope.
But the best chance of finding signs of life in the exoplanet atmosphere will come from the next generation of giant ground telescopes, including the Extremely Large Telescope, Thirty Meter Telescope and the 25.4-meter giant Magellan telescope with a mirror diameter of 39 meters. These telescopes are under construction and are ready to start collecting data by 2030.
Astronomers know that super earth has elements that support the existence of life, but livable does not mean that there are people living above. Life on Earth may be just a unique accident until researchers find evidence of life elsewhere. Although there are many reasons why habitable planet will not show signs of life, if astronomers observe these super habitable super earths and find nothing in the next few years, humans may be forced to conclude that "the universe is a lonely place."
