Shulou(Shulou.com)11/24 Report--

According to news on October 3, there are tens of billions of "super-Earths" in the Milky way alone, which are more common and more suitable for human habitation than the earth we now live in.

Astronomers often find extrasolar planets orbiting stars and call them "exoplanets". In the summer of 2022, the NASA team responsible for the transit exoplanet survey satellite discovered several particularly interesting exoplanets that were orbiting in the habitable zone of their parent star.

One of the planets is 30% larger than Earth and orbits the star in less than three days. The other planet is 70% larger than Earth, and there may be a deep sea on the surface. These two exoplanets belong to super-Earth. they are larger than Earth but smaller than planets such as Uranus and Neptune.

Earth is still the only known place in the universe where life exists, so it seems logical to focus the search for life on Earth-like planets. Research shows that the most likely target for astronomers to find life on other planets is super-Earth.

Most super-Earths revolve around cold dwarfs with lower mass and a much longer lifespan than the sun. Scientists have found that the super earth orbits 40% of the cold dwarfs they have observed. Based on this calculation, astronomers estimate that there are tens of billions of super-Earths in the habitable zone in the Milky way alone, and that there may be liquid water on them. Since all life on Earth needs water, water is considered to be a key factor for a habitable planet.

According to current projections, about 1/3 of exoplanets are super-Earths, making them the most common type of exoplanets in the Milky way. The nearest exoplanet is only six light-years from Earth. It can be seen that our solar system is so unusual because it does not have a super-Earth with a mass between Earth and Neptune.

Another reason that super-Earths are the most ideal target for life is that they are easier to discover and study than Earth-sized planets. Astronomers detect exoplanets in two ways. One is the gravitational effect of the planet on its parent star, and the other is that the star's light dims briefly as the planet passes in front of the parent star. Both methods are easier for larger planets.

Modern astrobiologists are exploring why planets are suitable for life. It turns out that the earth is not the best of all the worlds where life is possible. For most of its 4.5 billion-year history, the earth was unfit for humans and other larger creatures to live in. The simulation shows that the long-term livability of the earth is not inevitable, but there is a lot of chance. It can even be said that human beings are so lucky to be alive.

The researchers listed a series of attributes that make the planet very suitable for life. Larger planets are more geologically active, a feature that scientists believe will promote biological evolution. As a result, the most habitable planet is about twice the mass of Earth and 20% to 30% larger than Earth. It will also have an ocean shallow enough that light can shine on life on the ocean floor, with an average temperature of 25 degrees Celsius.

In addition, it will have a thicker atmosphere than Earth to act as an "insulation blanket". Finally, such a planet will orbit a star older than the sun to allow life to develop for a longer time, and it will have a strong enough magnetic field to withstand cosmic radiation. Scientists believe that the combination of these attributes will make a planet super habitable.

According to this definition, the super-earth has many of the properties of a super-habitable planet. So far, astronomers have discovered 24 super-Earth exoplanets that are theoretically more habitable than Earth, if not the best of all possible worlds.

Recently, an exciting new discovery has been added to the list of habitable planets. Astronomers have begun to discover exoplanets thrown out of star systems, possibly billions of such planets roaming the Milky way. If a super earth ejects from its star system and has a dense atmosphere and water, it can sustain life for tens of billions of years, far longer than life on Earth can last before the death of the sun.

To detect life on distant exoplanets, astronomers will look for biological features that can be detected in the planet's atmosphere, that is, biological by-products.

NASA's James Webb Space Telescope was designed before astronomers discovered exoplanets, so it is not optimized for exoplanet research. But it can do some scientific work in this area, and plans to target two potentially habitable super-Earths in its first year of operation. Another group of super-Earths with huge oceans discovered in the past few years, and planets discovered this summer, are also the targets of the James Webber telescope.

But the best chance of finding signs of life in exoplanet atmospheres will come from the next generation of giant ground-based telescopes, including Extremely Large Telescope, Thirty Meter Telescope and the 25.4m giant Magellan telescope with mirror diameters of 39m. These telescopes are under construction and are ready to start collecting data by 2030.

Astronomers know that the super earth has elements that support the existence of life, but being habitable doesn't mean it's inhabited. Until researchers find evidence of life elsewhere, life on Earth may just be a unique accident. Although there are many reasons why there are no signs of life on habitable planets, if astronomers observe these super-livable super-Earths and find nothing in the next few years, humans may be forced to conclude that "the universe is a lonely place".

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