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According to scientists, our Sun will gradually fade away. At that time, life on the planet will also share the same fate...
MANY SUPER EARTHS FOUND - BIG OPPORTUNITY?
Modern astronomers often discover planets orbiting stars outside the Solar System - they are called exoplanets. But in the summer of 2022, a group of scientists working on NASA's Transiting Exoplanet Survey Satellite (TESS) found some particularly interesting planets orbiting the habitable zone (Goldilocks) of their parent stars.
Among them is a planet larger than Earth by 30% and completes its orbit around its star in less than 3 days - it's the super Earth LP 890-9b, located 100 light-years away from us.
Another exoplanet, 70% larger than Earth and potentially having a gigantic liquid ocean - it's the super Earth TOI-1452b, orbiting a red dwarf star about 100 light-years away from us.
These two exoplanets are identified by scientists as super Earths - meaning they have a larger mass than Earth but are smaller than the 'ice giants' in the Solar System like Uranus and Neptune.
Most recently, Japanese scientists also discovered a super Earth named Ross 508 b, four times the size of Earth, orbiting the red dwarf star Ross 508, located 37 light-years away from us in the Serpens constellation. Ross 508 b, with a year equal to only 10.8 Earth days, lies on the inner edge of the 'habitable zone' around its host star.
Until now, Earth remains the only known place in the universe with life. It seems reasonable to focus on searching for life on Earth-like copies - planets with characteristics similar to Earth. However, studies have shown that the best chance astronomers may find life on another planet could be on a super Earth - similar to those recently discovered.
Most super Earths orbit cool dwarf stars, have lower mass, and live much longer than our Sun.
Astronomers estimate that there are tens of billions of super Earths in potentially habitable zones, where liquid water could exist, only within the Milky Way. Since all life on Earth uses water, it is considered crucial for the possibility of life.
Based on current predictions, about one-third of all exoplanets are super Earths, making them the most common type of exoplanet in the Milky Way. The closest super Earth is only 6 light-years away from our planet.
Another reason that makes super Earths an ideal target in the search for life is that they are much easier to detect and study than planets the size of Earth. The reason is:
Until now, astronomers have employed two methods to detect exoplanets. One is searching for the gravitational effect of a planet on its parent star, and the other is looking for the brief dimming of a star's light as a planet passes in front of it. Both of these detection methods are much easier with a planet larger than Earth.
WILL SUPER EARTHS 'PRESERVE' LIFE LONGER THAN EARTH?
Over 300 years ago, German philosopher Gottfried Wilhelm Leibniz argued that Earth is the 'best of all possible worlds for life.' However, modern astronomers have uncovered a larger issue by questioning what makes a planet capable of sustaining life. It turns out Earth is not the best world among all potential life-harboring worlds in the universe.
Due to Earth's geological activity and the Sun's brightness variations, the climate has changed over time, fluctuating from hot to icy cold across the entire planet. Earth has been inhospitable to larger human-like creatures for most of its 4.5 billion-year history. Therefore, life on this planet has been a fortunate evolutionary process for humanity.
Researchers have compiled a list of attributes that make super Earths highly conducive to life, specifically:
Larger planets are more likely to exhibit geological activity, a feature scientists believe will enhance the biological evolution process. Therefore, the most habitable planets will have a mass nearly double that of Earth and a volume larger by 20% to 30%. It will also boast oceans deep enough to encourage life to thrive at the ocean floor, with an average temperature of 25°C.
Such an exoplanet will possess a thicker atmosphere than Earth, acting like an insulating blanket. Lastly, such a planet will orbit an older star than the Sun to support prolonged life, and it will also have a strong magnetic field to shield against cosmic radiation. Scientists believe that these combined attributes will make a habitable super Earth.
By definition, a super Earth has many attributes of a potentially habitable super planet. To date, astronomers have identified over 1,600 super Earths - theoretically more habitable candidates than Earth - in the search for potentially life-supporting worlds.
Recently, scientists have added an intriguing addition to the list of potentially habitable exoplanets. Astronomers have started exploring planets beyond the Solar System that have been ejected from their star systems. If a super Earth is ejected from its star system, with a dense atmosphere and a water-rich surface, it could sustain life for tens of billions of years, much longer than life on Earth could exist before our Sun 'dies.'
According to data released in June 2022 from the Gaia space observatory (European Space Agency - ESA), the Sun is currently about 4.57 billion years old. Around 8 billion years old, the Sun will reach its maximum temperature. Afterward, it will cool and expand, becoming a red giant star. Later, the Sun will enter the final stage of its life cycle.
IS THE UNIVERSE A LONELY PLACE?
In the quest to detect life on distant exoplanets, astronomers will search for biological structures, by-products of biology that may be detectable in the atmosphere of those exoplanets.
NASA's James Webb Space Telescope was designed before astronomers discovered exoplanets, so it's not optimized for exoplanet research. However, it can perform some of these scientific tasks and is planned to target two potentially habitable super Earths in its first years of operation. Other super Earths with vast oceans discovered in recent years, as well as planets found this summer, are also compelling targets for scientific exploration.
But the best chance to search for signs of life in the atmosphere of exoplanets will come with the next generation of massive ground-based telescopes: the 39-meter Extremely Large Telescope, the 30-meter Telescope, and the 25.4-meter Giant Magellan Telescope. These telescopes are currently under construction and will begin collecting data in the late 2020s.
Astronomers know that the ingredients for life are out there - in the vast and distant universe, but 'habitable' doesn't necessarily mean 'inhabited'!
Until researchers find evidence of life elsewhere, the possibility of life on Earth may be a unique stroke of luck. If, in the coming years, astronomers scrutinize these potentially habitable super Earths and find nothing, humanity may be forced to conclude: The universe is a lonely place!
Source: Space.com
