This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: This summer, exoplanet science—the study of planets orbiting stars beyond our sun—took a big step forward. 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 recognizable "W" of the constellation Cassiopeia. But don't squint—it appears some 10,000 times fainter than the faintest star you can see with your naked eye. 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 liquid water on its surface. Previous observations of LHS 1140b with the James Webb Space Telescope ruled out 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 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, thought to be more stable and long-lived. Secondary atmospheres persist around their planets and can be studied by astronomers.
On Earth, our secondary atmosphere has been with us for billions of years, and its chemical balance reflects the combined effects of geology, chemistry and, ultimately, life. LHS 1140b orbits a red dwarf star about one-fifth the mass of our sun but some 300 times fainter. However, as viewed from Earth, the star dims with a regular dip every 24.7 days.
From the size of the brightness dip, scientists from the team that discovered the planet in 2017 estimated it to be 1.7 times larger than Earth. Subsequent observations indicated the planet has just over five times Earth's mass. Such "super-Earths" are among the least massive planets we can currently detect and represent some of the best candidates for detecting life beyond our solar system.
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