New Delhi, April 17 An Indian-origin astrophysicist-led study, published on Thursday, found the strongest hints of alien life yet in an exoplanet more than 120 light-years away from Earth.
Calling the hints “exciting” Professor Nikku Madhusudhan from the University of Cambridge’s Institute of Astronomy in the UK, said that “the signal came through strong and clear.”
Using data from the next-generation James Webb Space Telescope (JWST), Madhusudhan and team detected the chemical fingerprints of dimethyl sulphide (DMS) and/or dimethyl disulfide (DMDS), in the atmosphere of the exoplanet K2-18b.
K2-18b is 8.6 times as massive and 2.6 times as large as Earth and lies 124 light-years away in the constellation of Leo.
DMS and DMDS are molecules from the same chemical family, and both are predicted to be biosignatures.
On Earth, these are only produced by life -- primarily microbial life such as marine phytoplankton.
While an unknown chemical process may be the source of these molecules in K2-18b’s atmosphere, the results are the strongest evidence, yet that life may exist on a planet outside our solar system, said the team in the paper detailed in The Astrophysical Journal Letters.
“We didn’t know for sure whether the signal we saw last time was due to DMS, but just the hint of it was exciting enough for us to have another look with JWST using a different instrument,” said Professor Madhusudhan, who led the research.
The earlier, tentative, inference of DMS was made using JWST’s NIRISS (Near-Infrared Imager and Slitless Spectrograph) and NIRSpec (Near-Infrared Spectrograph) instruments, which together cover the near-infrared (0.8-5 micron) range of wavelengths. The new, independent observation used JWST’s MIRI (Mid-Infrared Instrument) in the mid-infrared (6-12 micron) range.
Notably, the latest observations reached the ‘three-sigma’ level of statistical significance -- meaning there is a 0.3 per cent probability that they occurred by chance.
To reach the accepted classification for scientific discovery, the observations would have to cross the five-sigma threshold, meaning there would be below a 0.00006 per cent probability they occurred by chance.
The researchers said between 16 and 24 hours of follow-up observation time with JWST may help them reach the all-important five-sigma significance.
The study showed that the concentrations of DMS and DMDS in K2-18b’s atmosphere are very different than on Earth. From below one part per billion by volume on Earth, they are estimated to be thousands of times stronger -- over ten parts per million -- on K2-18b.
“This could be the tipping point, where suddenly the fundamental question of whether we’re alone in the universe is one we’re capable of answering.”
"While the results are exciting, it’s vital to obtain more data before claiming that life has been found in another world," Madhusudhan said.
James Webb is an international programme led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.
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