Signs of life outside our solar system could be detected in two to three years, experts say after rethinking the types of planets that might be habitable.
Researchers are primarily looking for planets that are similar in size, mass, temperature, and atmospheric composition to Earth. However, astronomers at the University of Cambridge believe there may be a more promising possibility after recent research showed that “mini-Neptune” is more than twice the radius of Earth and more than eight times as massive. can also live.
They have now identified a new class of habitable exoplanets, called the Hycea planets – hot, ocean-covered, and hydrogen-rich – that are more numerous and more observable than Earth-like planets. Mini-Neptune, known as K2-18b, is one, and many more could exist.
“Hyceans are basically a water world with a hydrogen-rich atmosphere,” says Dr. Nikku Madhusudhan, lead author of the study from Cambridge University. He said a focus on Hyceans could accelerate efforts to find extraterrestrial life.
“We said we could see the first biosignature detection in two to three years if these planets had life,” he said, adding that the James Webb Space Telescope – Starting in November – can make searching easier.
Madhusudhan said the small size of Earth-like planets compared to sun-like stars results in weak atmospheric signatures, making it difficult to find signs of life.
However, Hyceans could be more than twice the Earth’s radius for a planet, roughly 10 times its mass, and significantly hotter, with an average atmospheric temperature of close to 200°C.
Larger planets are not only more abundant than Earth-sized ones, they are also easier to find, and allow for easier viewing of their atmospheres, Madhusudhan said.
In addition, the composition of the Hycean planet allows the discovery of a wider range of molecules that could indicate the existence of life.
Write on Astrophysics JournalThe team says a Hycean planet is defined as a hydrogen-rich atmosphere, a rocky core that makes up at least 10% of the planet’s mass, and a layer of water that makes up 90% of the planet’s mass.
Life might even occur on the dark side of the planet the team dubbed the “dark Hyceans”. These sit near their star and are blocked by the tides, meaning that the same side of the planet is always in the light – and may be too hot to be habitable.
The team says that all life on the Hyceans must be aquatic because the planets would be covered by a layer of water by definition. But what such a life is like is an open question, according to Madhusudhan.
“At least microbial life should be possible,” he said, adding that that’s how life began on Earth.
Prof. Beth Biller, exoplanet of the Institute for astronomy at the University of Edinburgh and not involved in research, welcomed the work. “There is such diversity among the exoplanets discovered so far, and it makes perfect sense to also examine non-Earth planets that might host life,” he said.
However, Biller added that finding biosignatures on the Hycean planet is still difficult. “Finding biosignatures for Earth’s twin has been extremely difficult – to a large extent relying on proving that the atmosphere is out of balance by recognizing combinations of various biosignature gases that should not exist together in equilibrium. In principle, this is also possible for the Hycean planets, but obviously without Earth as an example, it is more difficult to rule out false alarms in individual cases.
Biller said that for both types of planets, data from a large number of objects would be needed to understand which ones might be habitable.
“[The James Webb space telescope] will actually provide some very interesting spectra of the Hycean planets in the next few years, but it’s still hard to say whether those spectra are conclusive,” he said.
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