This summer, exoplanet science — the study of planets orbiting stars beyond our sun — took a big step forwards.

Reports of helium gas escaping from the atmosphere of LHS 1140b propelled this exoplanet from the pages of scientific journals into the mainstream media.

LHS 1140b orbits a faint, red star within the constellation of Cetus — named after a whale-like sea monster in Greek mythology — and just next to the easily recognisable “W” of the constellation Cassiopeia. But don’t squint — it appears some 10,000 times fainter than the feeblest star you can see with your naked eye.

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This exoplanet is of particular interest because it is a potentially rocky world within the “habitable zone” of the star it orbits. This means it may have a temperature that could allow for liquid water on its surface.

Just possibly, it could support the existence of life.

What does the presence of helium mean?

Previous observations of LHS 1140b with the James Webb Space Telescope ruled out the existence of a hydrogen-rich atmosphere — a so-called “primary” atmosphere that is thought to form in-step with young planets and is soon lost to space.

Astronomers think that all rocky planets may possess a primary atmosphere and then lose it shortly after they form. This is a short, transient phase in their story.

However, the reported observation of helium may indicate a “secondary” atmosphere,........

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