The search for alien life has been boosted after an atmosphere was detected surrounding an Earth-like planet for the first time.

The discovery provides the strongest evidence yet that worlds with conditions similar to our own in with the potential to support life could exist beyond our solar system, say American scientists.

Nearly a decade after discovering LHS 1140b, a rocky exoplanet in the “habitable zone” of a nearby low-mass star, a new study reveals the object may have its own atmosphere.

Study lead author Dr Collin Cherubim, of Harvard University, said: “An atmosphere is essential for a planet to support life as we know it.

“This is the first time anyone has found an atmosphere on a rocky planet in the habitable zone of another star.”

University of Florida Assistant Professor of Astronomy Jason Dittmann, who first discovered LHS 1140b in 2016, is co-author of the new study, published in the journal Science.

He said: “The exciting part about this paper, and why I think it was accepted into Science, was that this is the first time that we’re seeing a rocky, Earth-like planet that could still have an atmosphere.”

The Magellan Clay telescope at Las Campanas Observatory in Chile showed proof of helium escaping from the planet.

But the planet’s age signals it would have run out of helium unless it was replenishing its own supply, pointing to the potential of an atmosphere.

In 2016, Dr Dittmann used ground-based surveys to search for stars whose light briefly dimmed as orbiting planets passed in front of them.

To understand if the stars were dimming due to wispy clouds or humidity blowing through on Earth, he trained a machine learning algorithm to decipher which signals were caused by our weather and which were because of a passing planet.

The method helped Dr Dittmann find LHS 1140b.

Considering the type of star it orbits, he said the planet’s temperature should be similar to Earth’s.

It’s made of rock instead of gas, is around 48 light years away, and there is also a second planet in the system, LHS 1140c, which is located outside the habitable zone of its system.

Other rocky planets discovered within the past decade or so lost their atmospheres over time.

Considering the age of LHS 1140b and the lack of atmospheres by similar planets, Dr Dittmann and his colleagues didn’t expect to find helium.

He said: “We were getting to the point in the field where maybe all of these planets don’t have an atmosphere, and we need to look at ones around sun-like stars instead of smaller stars.

“And then finally here is actually one with an atmosphere, and it happens to be the one that I had spent so many hours working on.”

After originally discovering the planet, Dr Dittmann requested X-ray data from the planetary system.

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