A new class of habitable exoplanets is a major step forward in the search for life

news/tmb/2021/new-class-of-habitable.jpg" data-src="https://scx2.b-cdn.net/gfx/news/hires/2021/new-class-of-habitable.jpg" data-sub-html="Astronomers have identified a new class of habitable planets, dubbed ‘Hycean’ planets – hot, ocean-covered planets with hydrogen-rich atmospheres – which could represent a big step forward in the search for life elsewhere. Credit: Amanda Smith, University of Cambridge">

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A new class of exoplanets that is completely different from our group but can support life, has been identified by astronomers, which could significantly accelerate the search for life outside our solar system.

In the search for life elsewhere, astronomers mostly look for planets of similar size, mass, temperature, and atmospheric composition. However, astronomers from the University of Cambridge believe there is a more promising possibility.

Researchers have identified a new class of habitable planets, dubbed “Hycean” planets – hot planets covered in oceans and hydrogen-rich atmospheres – that are more abundant and observable than Earth-like planets.

The researchers say the results, reported in Astrophysics Journal, could mean that finding vital fingerprints of life outside our solar system in the next two or three years is a real possibility.

“The Hessian planets open up entirely new avenues in our search for life elsewhere,” said Dr Niko Madhusudan of the Cambridge Institute of Astronomy, who led the research.

Many of the major Hycean candidates identified by the researchers are larger and hotter than Earth, but still have properties that host large oceans that could support large oceans. microbial life Similar to those found in some of the most extreme aquatic environments on Earth.

These planets also allow for a much wider habitable zone, or “Goldilocks Zone,” compared to Earth-like planets. This means that they can still support life even if they are outside the range where a planet similar to Earth must exist in order to be habitable.

Thousands of exoplanets have been discovered since the first exoplanets were discovered nearly 30 years ago. Most planets are between Earth and Neptune in size and are often referred to as ‘super Earths’ or ‘mini Neptunes’: they can mostly be rocky planets or ice giants with hydrogen-rich atmospheres, or something in between.

Most small Neptunes are more than 1.6 times the size of Earth: smaller than Neptune but too large to have a rocky interior like Earth’s. Previous studies of the planet found that the pressure and temperature under a hydrogen-rich atmosphere would be too high to support life.

However, recent research by Madhusudan’s team on miniature Neptune K2-18b found that under certain conditions these planets could support life. The results lead to detailed investigations into the various characteristics of planets and stars that make these conditions possible, what exoplanets might meet these conditions, and whether their vital signs can be observed.

The investigation led the researchers to identify a new class of planets, the Hycean planets, with vast oceans of large planets beneath a hydrogen-rich atmosphere. The Hycean planets can be 2.6 times larger than Earth and have an atmospheric temperature of around 200 °C, but ocean conditions can be similar to those that gave rise to microbial life in Earth’s oceans. These planets also include the gradually closing Hycean world that may have habitable conditions only on its eternal night side, and the “cold” Hycean world that receives little radiation from its star.

Planets of this size dominate the known exoplanet group, although they have not been studied in as much detail as super-Earths. It’s possible that the Hycean world is very common, meaning that the most promising places to look for life elsewhere in the galaxy may be hiding in plain sight.

However, size alone is not sufficient to determine whether a planet is a Hycean type: other aspects such as mass, temperature, and atmospheric properties are required for confirmation.

When trying to determine conditions on a planet several light-years away, astronomers first need to determine whether the planet is located on the Residential area From the star, then look for molecular markers to infer the structure of the planet’s atmosphere and internals, which control surface conditions, the existence of oceans, and the possibility of life.

Astronomers are also looking for some biometric fingerprints that could indicate the possibility of life. Most often these are oxygen, ozone, methane, and nitrous oxide, all of which are present on Earth. There are also a number of other biomarkers, such as methyl chloride and dimethyl sulfide, which are less abundant on Earth but could be promising indicators of life on planets with hydrogen-rich atmospheres where oxygen or ozone may not be abundant.

“Basically, when we looked for these distinct molecular signatures, we focused on Earth-like planets, which are a reasonable place to start,” Madhusudan said. “But we think the Hycean planet presents a better chance of finding more biometric fingerprints.”

“It’s interesting that habitable conditions exist on a planet so different from Earth,” said co-author Anjali Payet, also from Cambridge.

Madhusudhan and his team found that a number of terrestrial biomarkers that are predicted to be present in the Hycean atmosphere will be easily detected through spectroscopic observations in the near future. The large size, high temperature, and hydrogen-rich atmosphere of the Hycean planet make its atmospheric signatures more detectable than Earth-like planets.

The Cambridge team has identified a large sample of potential Hycean worlds that are prime candidates for detailed studies using next-generation telescopes, such as the James Webb Space Telescope (JWST), due for launch later this year. this planet All red dwarfs orbit between 35-150 light years: close to astronomical standards. JWST’s planned observations of a promising candidate, K2-18b, could lead to the discovery of one or more biosignature molecules.

“The discovery of biometric fingerprints will change our understanding of life in the universe,” said Madhusudan. “We need to be open about where we hope to find life and what life forms are like, because nature continues to surprise us in often unimaginable ways.”

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