New species of ocean-covered “Hycean” exoplanets might help life

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When it comes to looking for life elsewhere in the universe, we tend to be very earth-centered: we look for planets similar to our own, provided that life elsewhere is similar to us and requires similar conditions. However, astronomers at Cambridge University have identified a new exoplanet that, while very different from Earth, could nonetheless support life.

The new planet class is known as the “Hycean” planet, which means an ocean-covered world with abundant hydrogen in its atmosphere. The researchers believe that these type of planets could be widespread, and since they are potentially habitable, this greatly increases the possible locations for finding life outside of our solar system.

Artist’s impression of a Hycean planet. Amanda Smith

“Hycea planets open a whole new path in our search for life elsewhere,” said lead researcher Nikku Madhusudhan of the University of Cambridge’s Institute of Astronomy in a statement.

These planets are typically up to 2.6 times larger than Earth and can also be hotter with atmospheric temperatures of up to 200 degrees Celsius. Despite these high temperatures, however, their oceans could still host microbial life, as suggested by another recent study of a large exoplanet with a hydrogen-rich atmosphere. This study found that there may be liquid water on the planet’s surface below its atmosphere. If the same is true of Hycea planets, the habitable zone – the area around a star that a planet must orbit for liquid water to exist on its surface – could be larger for these planets than for other types of planets.

“Essentially, we focused on Earth-like planets in our search for these different molecular signatures, which is a reasonable place to start,” said Madhusudhan. “But we believe that Hycea planets offer a better chance of finding multiple traces of biosignatures.”

Biosignatures are chemical cues of life and are one of the main ways researchers look for life elsewhere in the universe.

“Recognizing biosignatures would change our understanding of life in the universe,” said Madhusudhan. “We have to be open about where we expect life and what form this life could take, since nature surprises us again and again in often unimaginable ways.”

The research is published in the Astrophysical Journal.

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