Astronomers discover 1st atmosphere around a rocky Earth-like planet in the habitable zone

Astronomers discover 1st atmosphere around a rocky Earth-like planet in the habitable zone

Astronomers have detected an atmosphere surrounding a rocky, Earth-like planet orbiting within the habitable zone of another star for the first time. The discovery, published in the journal Science, centers on the exoplanet LHS 1140 b, located about 48 to 49 light-years from Earth.

The planet orbits a red dwarf star. Because it sits in the "Goldilocks zone," environmental conditions and temperatures are within a range that could support liquid water on the surface. Lead author Collin Cherubim, who recently earned his Ph.D. In Earth and Planetary Sciences from Harvard University, stated that an atmosphere is essential for a planet to support life as we know it.

LHS 1140 b is larger than Earth.

The Helium Signature

Researchers used the Warm Infrared Echelle (WINERED) Spectrograph on the Magellan telescope at Las Campanas Observatory in Chile to identify helium escaping from the planet's upper atmosphere. This represents the first direct identification of an atmospheric species for any rocky exoplanet, regardless of whether it is in a habitable zone.

The detection was based on a theoretical planetary evolution model developed by Cherubim. The team observed a rare alignment where LHS 1140 b and another planet transited their star on the same night. While the other planet showed no evidence of an atmosphere, LHS 1140 b exhibited a direct helium signature.

The discovery is particularly notable because red dwarf stars—the most common type of star in the universe—often release extreme radiation, such as solar flares, that strips atmospheres from orbiting planets. However, the star orbiting LHS 1140 b is roughly 6 billion years old and is described as quiet. Scientists believe the atmosphere has likely survived for more than three billion years.

Habitability and Composition

The presence of an atmosphere provides a shield against radiation and helps trap water, making LHS 1140 b a primary target for astrobiology. According to Cherubim, the planet has the main ingredients essential for life: a rocky composition, a temperature that supports liquid water, and an atmosphere.

Parallel Research in the TRAPPIST-1 System

While LHS 1140 b has provided a confirmed detection, other studies are pursuing similar goals in the TRAPPIST-1 system, located about 40 light-years away. Astronomers using the James Webb Space Telescope (JWST) have focused on TRAPPIST-1 e, the fourth planet in that system.

Observations performed in 2023 were unable to rule out an atmosphere on TRAPPIST-1 e, though they did rule out a primary, hydrogen-based atmosphere. Néstor Espinoza, an astronomer at the Space Telescope Science Institute, stated that the planet is unlikely to have a carbon-dioxide-rich atmosphere like Venus or Mars, pointing instead toward a nitrogen-heavy one similar to Earth or Titan.

The JWST has already ruled out an atmosphere on the innermost planet of that system, TRAPPIST-1 b. For TRAPPIST-1 e, the "dream is still alive," according to Espinoza, as researchers work to complete a follow-up program of 15 observations.

Next Steps

The confirmation of an atmosphere on LHS 1140 b validates the use of ground-based observations searching for escaping gases as a tool for studying rocky exoplanets. Cherubim intends to determine the full composition of the atmosphere and investigate if the planet possesses surface oceans.