Super-Earths are larger, more common, and more habitable than Earth itself – and astronomers are discovering billions more than they think are out there.

Astronomers Now Regularly Find planets orbiting stars outside the solar system They are called exoplanets. But in the summer of 2022, the teams working on NASA’s Transiting Exoplanet Survey Satellite Some particularly interesting planets were found orbiting in the habitable zones of their parent stars.

is a planet 30% larger than Earth and orbits its star in less than three days. second is 70% larger than Earth And could host a deep sea. these are two exoplanets super earth – More massive than Earth but smaller than ice giants like Uranus and Neptune.

I am professor of astronomy the galactic core, which studies distant galaxies, astronomy And exoplanets, I closely follow the search for planets that may host life.

Earth is still the only place in the universe that scientists consider to be the home of life. It would seem logical to focus the search for life on a clone of Earth – planets close to earth, But research has shown that astronomers’ best chance of finding life on another planet is likely on the recently found super-Earth.

An image showing Earth and Neptune with a medium-sized planet in the middle.

A super-Earth is any rocky planet that is larger than Earth and smaller than Neptune.
aldarone, CC BY-SA

simple and easy to find

Most super-Earths orbit cold dwarf stars, which have less mass and live longer than the Sun. There are hundreds of cool dwarf stars for every Sun-like star, and scientists have found orbiting super-Earths 40% of cool dwarves He has seen. Using that number, astronomers estimate that there are tens of billions The number of super-Earths in the habitable zones where liquid water can exist in the Milky Way alone. Since all life on earth uses water, water is considered vital for living.

Based on current estimates, approximately a third of all exoplanets There are super-Earths, making them the most common type of exoplanet in the Milky Way. is the closest six light years away from Earth. You could even say that our solar system is unusual because it does not have any planets with a mass between that of Earth and Neptune.

A diagram showing how a planet passing in front of a star can dim the light.

Most exoplanets are discovered by observing how they reduce the light coming from their parent stars, so larger planets are easier to find.
Nikola Smolensky, CC BY-SA

Another reason why super-Earths are ideal targets in the pursuit of life is that they are so easy. explore and study compared to Earth-sized planets. Astronomers use two methods to detect exoplanets. One looks for the gravitational effect of a planet on its parent star and the other looks for the dimming of a star’s light when it passes in front of the planet. Both of these detection methods are easier with the larger planet.

Super-Earths Are Super Habitable

300 years ago, the German philosopher Gottfried Wilhelm Leibniz argued that the Earth “best of all possible worldsLeibniz’s argument was intended to address the question of why evil exists, but modern astrologers have explored a similar question as to whether a planet is hospitable to life. I am not the best.

Because of Earth’s tectonic activity and changes in the Sun’s brightness, climate has changed over time from ocean-boiling hot to planet-wide, deep-cold. Earth has been uninhabited for humans and other large organisms for most of its 4.5 billion year history. Simulations suggest longer duration Earth’s habitability was not inevitableBut it was a matter of coincidence. Man is really lucky that he is alive.

researchers have come up with a list of properties Which make the planet very favorable for life. Larger planets more likely to be geologically active, a feature scientists think promote organic growth, So the most habitable planet would be about twice the mass of Earth and 20% to 30% larger by volume. It will also have oceans that are large enough for light to stimulate life up to the ocean floor and have an average temperature of 77 °F (25 °C). It will have a thicker atmosphere than Earth which will act as an insulating blanket. Eventually, such a planet would orbit a star older than the Sun to give life more time to develop, and would have a stronger magnetic field that protects from cosmic radiation, Scientists believe that these properties together will make a planet habitable.

By definition, a Super-Earth has many of the properties of a super habitable planet. To date, astronomers have discovered Two dozen super-Earth exoplanets Which, if not the best of all possible worlds, are theoretically more habitable than Earth.

Recently, there has been an exciting increase in the list of habitable planets. astronomers have Started the search for exoplanet that have been ejected from their star systemand may billions of them The galaxy is spinning. If a super-Earth is ejected from its constellation and its atmosphere is dense and watery, it could sustain life for tens of billions of yearsBefore the Sun dies, life on Earth can last much longer than that.

A world full of water in front of a dim star.

One of the newly discovered super-Earths, TOI-1452b, may have been covered in a deep ocean and may have been well-suited for life.
Benoit Goujon, University of Montreal, CC BY-ND

Detecting Life on a Super-Earth

To detect life on distant exoplanets, astronomers will look for biosignatures, byproducts of biology which are detectable in the atmosphere of a planet.

NASA’s James Webb Space Telescope was designed by astronomers before exoplanets were discovered, so the telescope is not optimized for exoplanet research. but it is capable of doing some of this science and is determined to Target two potentially habitable super-Earths in its first year of operation. There are also another group of super-Earths with giant oceans discovered in the past few years, as well as planets discovered this summer Attractive target for James Webb,

But the best chance of finding signs of life in exoplanet atmospheres will come with the next generation of giant, ground-based telescopes: 39-Meter Extremely Large TelescopeThe thirty meter telescope And this 24.5-meter Giant Magellan Telescope, All these telescopes are under construction and ready to start collecting data by the end of the decade.

Astronomers know that the ingredients for life are out there, but habitable doesn’t mean inhabited. Until researchers find evidence of life elsewhere, it is possible that life on Earth was a unique accident. While there are many reasons for a habitable world no signs of lifeIf, in the years to come, astronomers look at these super habitable super-Earths and find nothing, humanity may be forced to conclude that the universe is a lonely place.

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