Astronomers announce “stronger evidence so far” of life outside the solar system

A team of astronomers at Cambridge University announced Thursday that he detected the “most promising evidence” of potential life on a planet outside our solar system. However, some scientists manifest their skepticism.

There has been an intense debate in the scientific circles about whether the planet K2-18bwhich is 124 light years away of the land, in the constellation of Leo, can be a oceanic world capable of hosting microbial life.

In a statement published in, a team of British and American researchers has now announced that it has detected sulfide sulfide (DMS) and dimetyl disulfide (DMDs) sulfide signs in the K2-18B atmosphere.

On Earth, these two chemicals, there is a long time considered as “bioassine” indicating extraterrestrial life, only are produced by life forms – Most microscopic seaweed, such as marine phytoplankton.

The discovery, made with the James Webb (JWST) space telescope, was presented in a published Thursday in the magazine The Astrophysical Journal Letters.

Although an unknown chemical process may be the source of these molecules in the K2-18B atmosphere, The results are the strongest proof so far that there may be life on a planet outside our solar system.

The observations reached the “Three-sigma” level of statistical significance – which means that there is a probability of 0.3% that have occurred by chance.

To achieve acceptance for scientific discoveries, observations would have to exceed the five-sigma thresholdwhich means that the probability of having occurred by chance would be less than 0.00006%.

According to investigators, between 16 and 24 hours of observation time with JWST can help them achieve the important significance of five-sigma.

An earlier, the team of Madhusudhan It had the discovery of methane and carbon dioxide in the k2-18b atmosphere-which is 8.6 times more massive and 2.6 times larger than the earth.

It was the first time carbon -based molecules were discovered In the atmosphere of an exoplanet in the habitable zone of its star, and these results are consistent with the characteristics of one: a habitable world oceans under a hydrogen -rich atmosphere.

However, another, weaker signalindicated the possibility of something else happening in K2-18b.

“We were not sure if the sign we last saw DMS, but only the fact that we have seen it It was exciting enough to give another view of eyes with JWST with a different instrument, ”explains Nikku madhusudhan Researcher at the Cambridge Astronomy Institute and the main author of the study.

To determine the chemical composition of the atmospheres of distant planets, astronomers analyze the light of your mother star When the planet transitsthat is, pass in front of the star, seen from the earth.

When k2-18b moves, JWST gets detect a drop in shine Star, and a small fraction of stellar light passes through the atmosphere of the planet before reaching Earth.

The absorption of part of the star light in the atmosphere of the planet Leaves marks In the steward that astronomers can gather to determine the constituent gases of the exoplanet atmosphere.

The new observation used JWST MIDI (Mid-Infred Instrument) in the medium infrared range (6-12 microns).

“This is an independent line of evidence, with a different instrument From what we used earlier and a range of different wavelengths, where there is no overlap with previous observations, ”details Madhusudhan. signal came strong and clear“.

“It was incredible realization to see the results emerge and remain consistent along the extensive analyzes independent and robust tests, ”says Måns Holmbergresearcher at Space Telescope Science Institute in Baltimore, USA, and co-author of the study.

DMS and DMDs are molecules of the same chemical family and it is expected to be bioassinaturas. They have spectral characteristics that overlap in the observed wavelength range, although more observations help differentiate the two molecules.

However, the concentrations of DMs and DMDs in the atmosphere of K2-18b are very different from those of the earthwhere they are inferior to one part by a thousand million in volume. In k2-18b, it is estimated to be thousands of times stronger – More than ten parts per million.

“Previous theoretical works have foresaw that high sulfur -based gases such as DMS and DMDs would be possible in Hycean worlds,” says Madhusudhan. “And now we observe itaccording to what was foreseen. ”

Some skepticism

“Given everything we know about this planet, a Hycean world with An ocean full of life is the scenario that best suits To the data we have, ”says the investigator.

However, says Nikku Madhusudhan, “it is important that we are deeply skeptics in relation to our own resultsbecause only testing and testing again will we be able to reach a point where we have confidence in them. This is how science has to work“.

The prudence with which Madhusudhan faces the results of the study meets the skepticism with which they were received by some scientists.

The K2-18b has been considered the main candidate The “Planet Hycean”. These planets are not expected to host intelligent extraterrestrial life, but tiny microbes similar to those in the oceans From the land for a thousands of millions of years, explains the.

Some researchers question whether the currently proposed ocean planets will not be too close to your stars to support liquid water,-including the K2-18b, which orbits its star every 33 days.

An independent, conducted in 2022 by Raymond PierrehumbertProfessor of Planetary Physics at Oxford University, suggests that K2-18b is simply too hot to have life.

“If the planet had water, It would be infernally hot and uninhabitablesaid the investigator at AFP at the time. “Having lava oceans would be more plausible.”

Also Sara SeagerProfessor of Planetary Sciences in MIT, appeals to prudence, pointing to previous evidence of water vapor in the atmosphere of K2-18b that revealed to be a different gas.

Despite his prudence, Madhusudhan is enthusiastic about the perspectives his study opens. “From now on, we may look back and see that it was At this moment that the living universe was within our reach“Says the investigator.

“This can be the turning point, where we are suddenly able to answer the fundamental question of knowing If we are alone in the universe“He concludes.