Astronomers have made a significant breakthrough in the search for life beyond Earth by detecting an atmosphere around a rocky, Earth-like planet located in the habitable zone of another star. This discovery provides the most compelling evidence to date that planets with Earth-like temperatures and rocky compositions can exist beyond our Solar System, maintaining conditions that may be suitable for life.
“An atmosphere is essential for a planet to support life as we know it,” said lead author Colin Cherubim, who recently earned his Ph.D. in Earth and Planetary Sciences from Harvard University. “This is the first time anyone has found an atmosphere on a rocky planet in the habitable zone of another star.”
The study, published on July 16 in the journal Science, describes observations of helium escaping from LHS 1140 b — a rocky exoplanet located approximately 48 light-years from Earth. This signal confirms previous theoretical predictions about the presence of an atmosphere on the planet. LHS 1140 b orbits a red dwarf star in its habitable zone — a region around the star where temperatures and other environmental conditions could allow liquid water to remain on the planet’s surface.
While scientists have identified thousands of exoplanets, including several rocky worlds in habitable zones, confirming the presence of atmospheres on these planets has been one of the most challenging tasks. “Twenty years ago, we wondered if other Earth-like planets existed,” said Robin Wordsworth, the Gordon McKay Professor of Environmental Science and Engineering and Professor of Earth and Planetary Sciences at Harvard, who is also one of Cherubim’s thesis advisors. “Then we learned that they are common and found some in the habitable zone. The next question was whether any of them had managed to retain an atmosphere. Now we know that at least one has.”
This is the first confirmation that a rocky planet in the habitable zone has been able to retain its atmosphere for billions of years.
Model confirmed by telescope data
Cherubim and his colleagues developed a theoretical model predicting that the upper layers of LHS 1140 b‘s atmosphere would contain a significant amount of helium slowly escaping into space. The researchers tested this prediction using the Warm Infrared Echelle (WINERED) spectrograph at the Magellan Observatory in Chile. Their observations capitalized on a rare event when LHS 1140 b and another planet crossed in front of their star in one night. The second planet showed no signs of an atmosphere, while LHS 1140 b exhibited a clear signal of escaping helium, providing evidence of an atmosphere.
Cherubim’s co-advisor David Charbonneau, chair of the Harvard Astronomy Department and an astronomer at the Center for Astrophysics | Harvard & Smithsonian, initially doubted the success of the plan. The prediction was based on a mathematical model, and this type of signal had never been observed from a rocky world before. The study’s results changed his mind. “Colin analyzed the planets we know and predicted that this one would have a helium atmosphere,” said Charbonneau. “Then he managed to get telescope time, obtained the data, and the detection was statistically undeniable.”
This discovery suggests that astronomers can study the atmospheres of rocky exoplanets from Earth by looking for gases escaping into space. Astronomers estimate that LHS 1140 b‘s atmosphere has persisted for over three billion years, making the planet a particularly promising target for further observations. Cherubim hopes to determine the full chemical composition of its atmosphere and ultimately establish whether the planet has surface oceans or other features associated with habitability. He and his colleagues also plan to use the model to search for other rocky worlds with atmospheres. “This was a test of the model, and hopefully, it’s just the first of many future observations,” he added.
Source: Science Daily
