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Astronomers are now accustomed to discovering planets orbiting stars outside the solar world – they are called exoplanets. But in the summer of 2022, teams working on NASA’s Exoplanet Transit Survey Satellite discovered a few particularly interesting planets orbiting the habitable zones of their parent stars.
One planet is 30% larger than Earth (Opens in a new tab) His star orbits less than three days. The other is 70% larger than the earth (Opens in a new tab) and the deep host from the equal. These two are super-Earth exoplanets — larger than Earth but smaller than ice giants such as Uranus and Neptune.
I am a professor of astronomy (Opens in a new tab) who studies galactic hearts, distant galaxies, and astrobiology (Opens in a new tab) and exoplanets. I am closely following the search for planets that can host life.
The world is the only world where scientists know their place in life. It seems consistent to look for life on Earth clones – planets with properties close to Earth. But the research shows that the best chance astronomers have of finding life on another planet is likely to be on a super-Earth similar to the recent discoveries.
Related: “We may find life outside the solar system in twenty years,” says the researcher
Common and easy to find
Most orbit super-Earth cool dwarf stars, which are of lower mass and live much longer than the Sun. There are hundreds of cool dwarf stars in every star like the Sun, and scientists have found that 40% of the super-Earth orbits are cool dwarfs. (Opens in a new tab) they looked Astronomers estimate that number to be ten billion (Opens in a new tab) above the Earth in the habitable zones where liquid water can exist only in the Milky Way. Since all life on earth uses water, water is considered critical for habitability.
Current projections are based on about a third of all exoplanets (Opens in a new tab) They are super-Earths, making them the most common type of exoplanet in the Milky Way. The nearest is only 6 light years away (Opens in a new tab) of the Earth You could also say that our solar system is unusual, since there is no planet with a mass between Earth and Neptune.
Another reason super-Earths are the best targets in the search for life is that they are much easier to detect and study (Opens in a new tab) than the earth-sized planets. Astronomers use two methods to detect exoplanets. One looks for the effect of the planet’s gravity on the parent star and the other is the brief dimming of the star’s light as the planet passes in front of it. Both detection methods are easier with a larger planet.
Super Earths are super habitable
Over 300 years ago, German philosopher Gottfried Wilhelm Leibniz argued that Earth was “the best of all possible worlds.” (Opens in a new tab).” Leibniz’s argument was meant to be the question of why evil exists, but modern astrobiologists have looked at a similar question by asking what makes a planet hospitable to life. It turns out that Earth is not the best of all possible worlds.
Due to the tectonic activity of the Earth and changes in the brightness of the sun, the climate has shifted over time from a boiling ocean to a completely freezing cold planet. Earth has been uninhabitable to humans and other larger creatures for most of its 4.5-billion-year history. Simulations suggest that long-term habitability on Earth is not inevitable (Opens in a new tab)but it happened by chance. People are literally happy to be alive.
The researchers came up with a list of attributes (Opens in a new tab) which planets are very conducive to life. Larger planets are more likely to be geologically active, a feature that scientists believe promotes biological evolution. (Opens in a new tab). A habitable planet would therefore have roughly twice the mass of Earth and be between 20% and 30% larger in volume. It would also have oceans that are shallow enough to allow light to stimulate life down to the sea floor and an average temperature of 77 degrees Fahrenheit (25 degrees Celsius). It would have an atmosphere thicker than Earth’s which would act as an insulating layer. Finally, such a planet would have to orbit a star older than the Sun to develop a longer life and have a strong magnetic field that protects against cosmic rays. (Opens in a new tab). Scientists believe that these attributes combined would make the planet super habitable.
By definition, super-Earths have many attributes of a planet that is beyond habitable. To date, astronomers have found two dozen super-Earth exoplanets (Opens in a new tab) which are, if not the best of all possible worlds, theoretically more habitable than the earth.
Recently, the inventory of habitable planets has been exciting. Astronomers began to discover exoplanets (Opens in a new tab) who were ejected from the star system (Opens in a new tab)and it could be their billions (Opens in a new tab) wandering the milky way If a super-Earth were ejected from the star system and had a dense atmosphere and watery surface, it could support life for ten billion years. (Opens in a new tab)far longer than life on Earth could last before the sun dies.
Detection of life on Earth
To detect life on distant exoplanets, astronomers will look for biosignatures, products of biology (Opens in a new tab) which are detectable in the atmosphere of the planet.
NASA’s James Webb Space Telescope was designed before astronomers discovered exoplanets, so the telescope was not optimized for exoplanet research. But he can do something about that knowledge, and it’s aimed at two potentially habitable super-Earths in the first year of operations. Another set of super-terrestrial objects, including the giant oceans discovered a few years ago and the planets discovered this summer, are also forcing the target. (Opens in a new tab)s for Lacobo Webb.
But the best chances of finding signs of life in exoplanet atmospheres will come with the next generation of giant, ground-based telescopes: the 39-meter Very Large Telescope. (Opens in a new tab)Thirty Meter Telescope (Opens in a new tab) and the 25.4 meter Giant Magellan Telescope (Opens in a new tab). These telescopes are all under construction and should begin collecting data by the end of the decade.
Astronomers know that there are ingredients for life, but they are not habitable. Until researchers find evidence of life elsewhere, it is possible that life on Earth was a unique accident. Since there are many reasons why a habitable world does not have signs of life, if, in the years to come, astronomers look at these super-habitable earths and find nothing, humanity will be forced to conclude that the world is a deserted place.
Editor’s Note: The story has been updated to correct the size of the giant Magellan Telescope.
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