New Delhi, Apr 18 (PTI) Evidence of biological activity outside the solar system can potentially change the way the night sky is fundamentally perceived, from seeing it as a physical, inanimate sky to thinking of it as a “living sky”, astrophysicist Nikku Madhusudhan has said.

A professor of astrophysics and exoplanetary science at the University of Cambridge, Madhusudhan is the lead researcher on a study that has found fingerprints of dimethyl sulphide and dimethyl disulphide molecules on an exoplanet — K2-18 b — about 120 light years from Earth.

The molecules, known to be produced on Earth by marine organisms, are considered predictors of life or habitability on exoplanets.

The results of the study, published in The Astrophysical Journal Letters, are the strongest signs yet of life outside the solar system.

Madhusudhan told PTI Videos, “It is entirely possible that if we spend a few more observations on (K2-18 b), then, in a few years, we may be able to increase the significance substantially and very confidently detect these molecules.” Currently, the study provides evidence of “three-sigma” significance. The statistical term is an objective measure, indicating a 99.7 per cent confidence that the study’s results are not a “fluke”.

“Three sigma means you would still have a 0.3 per cent chance that it’s a statistical fluke — (about) three in a thousand chance of it being a fluke,” Madhusudhan said.

While this level of significance was seen “respectably”, when it comes to a scientific result carrying massive implications — such as ‘we might not be alone in the universe’ — “you want to be really, really sure”, according to the astrophysicist.

“When you have big breakthroughs, big paradigm shifts, you want to be really, really sure because it changes the very fabric of science and society in fundamental ways,” Madhusudhan said.

“So then, the measure of robustness there is that we want to be sure to a level that there is less than one part in a million chance of a fluke, which is a very, very, very small chance of a statistical fluke or a ‘just by chance’. We want to be that robust,” he added.

Born in India in 1980, Madhusudhan graduated from the Indian Institute of Technology (Banaras Hindu University), Varanasi, with an undergraduate degree in engineering.

He went on to pursue a masters in engineering in 2004 and a PhD in physics in 2009 from the Massachusetts Institute of Technology (MIT), US.

He held postdoctoral positions at multiple institutes, including MIT, before joining the University of Cambridge as faculty in 2013.

Over the past decade, the astrophysicist has made influential contributions to the field of exoplanetary science, especially on the atmospheres of “Hycean worlds” — a type of exoplanet entirely covered by an ocean beneath a hydrogen-rich air.

Madhusudhan’s team coined the term five years ago while trying to find planets potentially habitable, yet be big enough and have properties that can be observed using currently available technical instruments.

“So, we came up with this concept and K2-18 b is a good candidate for that. If you take the mass radius or equilibrium temperature of the planet. It matches that description,” said the astrophysicist, whose work has been recognised by the Yale Center for Astronomy and Astrophysics and the International Union of Pure and Applied Physics.

In 2023, Madhusudhan’s team made its first observations of K2-18 b using NASA’s James Webb Space Telescope.

“We found molecules, carbon-bearing molecules like methane and carbon dioxide in the atmosphere of this planet for the first time,” he said.

The findings also revealed “potential signs” of dimethyl sulphide, considered as a predictor of life on a Hycean world.

“So, it is entirely possible that if we spend a few more observations on this planet, (then) in a few years, we may be able to increase the significance substantially and very confidently detect these molecules,” Madhusudhan said.

Scientifically, the result has major repercussions because, if K2-18 b is established to be habitable, it must mean that “the universe is teeming with life”, the astrophysicist said.

“This can have a fundamental impact on how we think about the night sky, how we think about the universe,” he added.

“Because today, if you look out in the night sky, your impression of the sky is (of) a physical universe with physical objects like planets, stars and galaxies whereas we on Earth are the biological part of the universe,” Madhusudhan said.

He added, “However, if you detect life elsewhere, it changes that paradigm — because when you look at the night sky, you would be thinking of it as a living sky.” “And just that very act transforms us from a society, a civilisation that is Earth-based to a very cosmic entity. You’d suddenly realise that we are actually biologically sharing this universe with other planets, other species. And that is a fundamental shift in how we look at the universe and our place in the universe,” Madhusudhan said. PTI KRS SZM SZM