Astronomers from the University of Cambridge have identified a new class of exoplanet known as ‘Hycean’ planets in an exciting new discovery, which could greatly accelerate the search for life outside the solar system.
The new exo-planets, known as ‘Hycean’ planets are often larger and hotter than earth, however still have the characteristics to host large oceans with hydrogen rich atmospheres. This combination could allow microbial life to thrive in similar ways to that found in some of Earth’s most extreme aquatic environments. In addition, these planets also have a much wider habitable zone compared to other earth-like planets, meaning there is a higher potential for life to be supported. Within this ‘Goldilocks zone’, the temperature sits just right, so its not too hot and not too cold.
Since the first exoplanet was discovered nearly 30 years ago, thousands of planets outside our Solar System have been discovered, many of these being ‘super-Earths’ or ‘mini-Neptunes’. These two classes of planet are mainly rocky or ice giants, with hydrogen rich atmospheres. Excitingly, a recent study has shown that these planets with hydrogen-rich atmospheres have great potential to support life, leading researchers to identify a new class for the planets. Hycean planets.
“It's exciting that habitable conditions could exist on planets so different from Earth,” said co-author Anjali Piette, also from Cambridge.
To determine whether a planet is a ‘Hycean planet’, astronomers first determine whether the planet lies within the habitable zone of it’s star, then look for molecular signatures to infer the planet’s atmospheric and internal structure, which govern the surface conditions, presence of oceans and potential for life. Other aspects are taken into consideration such as mass, temperature and atmospheric properties. These planets can be up to 2.6 times larger than earth, with temperatures up to nearly 200 degrees Celsius. Such planets also include tidally locked ‘dark’ Hycean worlds, that may have habitable conditions only on their permanent night sides, and ‘cold’ Hycean worlds that receive little radiation from their stars.
However, what has promoted more excitation for researchers is that in fact, these Hycean worlds are likely quite common, leaving plenty of room for the exploration of already discovered exo-planets. As part of this exploration, a next-generation telescope called the James Webb Space Telescope will be used by The Cambridge team later this year, allowing them to locate planets between 35-150 light years away.
“Hycean planets open a whole new avenue in our search for life elsewhere,” said Dr Nikku Madhusudhan from Cambridge’s Institute of Astronomy, who led the research. “A biosignature detection would transform our understanding of life in the universe. We need to be open about where we expect to find life and what form that life could take, as nature continues to surprise us in often unimaginable ways.”
The researchers say the results, reported in The Astrophysical Journal, could mean that finding biosignatures of life outside our Solar System within the next few years is a real possibility.