Both planets could support water, even if the scientists do not know what its atmosphere is like. 

They claim that even if the planet's atmosphere is relatively thin in comparison to Earth's, or it is far thicker, it may still be a viable world for life and water. 

Orbiting around Teegarden's star, the worlds — dubbed Teegarden’s star b and c — were first detected in June 2019 by the Calar Alto Observatory's CARMENES survey. 

Two Earth-like planets just 12.5 light years from the solar system could harbour liquid water on their surfaces — and may therefore potentially also play home to alien life

The planets both whizz around on orbits that are very close to their star, meaning that the same side of each planet always faces Teegarden's star.

This phenomenon — dubbed 'tidal locking' — is the same phenomenon that keeps the near side of the moon facing the Earth.

Tidal locking may also help Teegarden's planets support life, researchers argue. 

Astrophysicists Amri Wandel of the Hebrew University of Jerusalem and Tel Aviv University's Lev Tal-Or calculated the kind of atmospheres that would be needed in order for Teegarden's planets to have liquid water on their surfaces.

The planets' tidal locking means that if they didn't have atmospheres then they would have both a hot and cold side — but with an atmosphere, there is the potential for winds to transport heat around their surfaces.

The duo found that as long as the planets have atmospheres that are between a third and 17 times as dense as the Earth's, there will probably be at least one region on one of the two world's that can support liquid water.

Tidally-locked planets like Teegarden's planets may be more likely to harbour liquid water and, by extension, life than their counterparts, Dr Wandel told the New Scientist.

On the Earth, surface temperatures vary between the poles and the equator, but to a relatively limited extent — whereas tidally locked planets can feature more extreme variations from one region to another

'This gives a wider range of possible atmospheres that allow for life,' said Dr Wandel.

In contrast, NASA astrophysicist Jessie Christiansen — who was not involved in the present study — told the New Scientist that tidally locked planets may instead present obstacles to the development of life.

For one thing, she explained, some experts think that having a day-night cycle is key for living organisms — something that would not be experienced on world's that always keep the same aspect facing their star

Furthermore, tidal locking can act to suppress the magnetic field of a planet — meaning that such bodies would be more exposed to harmful radiation from their host star.

Daily Mail

More about: planet