55JWST discovers ‘milestone’ confirming atmosphere of Earth-like exoplanet

55 Cancri e is a little bigger than Earth, but much smaller than the Solar System’s giant planets, such as Neptune.Credit: NASA, ESA, CSA, Dani Player (STScI)

55 Cancri is too hot to support life as we know it, but it could provide clues about Earth’s formation.

JWST discovers ‘milestone’ confirming atmosphere of Earth-like exoplanet 55 Cancri is too hot to support life as we know it, but it could provide clues about Earth’s formation. Written by Sumeet Kulkarni Twitter Facebook Email A planet covered in magma and with stars in the background. The planet 55 Cancri (author’s impression) orbits very close to the star.

Library Astronomers have announced the first discovery of an atmosphere surrounding a rocky planet outside our solar system using the James Webb Space Telescope (JWST)1. The planet may be covered in a magma ocean, making it incapable of supporting life as we know it, but scientists have learned from it that it is also a rocky planet and was once molten. You might even learn something about Earth’s early history. The discovery of a gas shell around an Earth-like planet is a major milestone in exoplanet research, says planetary scientist Sarah Seager of the Massachusetts Institute of Technology in Cambridge, who was not involved in the study. Earth’s thin atmosphere is essential for supporting life, and being able to detect an atmosphere on a similar terrestrial planet is a key step in the search for life outside the solar system. The planet studied by JWST, called 55 Cancri, orbits a sun-like star 12.6 parsecs away and is considered a super-Earth, a terrestrial planet that is slightly larger than Earth – in this case, about twice the radius of Earth, and more than eight times as heavy. Its atmosphere is likely rich in carbon dioxide or carbon monoxide, and its thickness can reach “up to a few percent” of the planet’s radius, according to a paper published today in Nature. Mysterious Planet Another reason 55 Cancri is uninhabitable is that it is very close to its star, about 1/65th the distance from Earth to the sun. Still, “it’s probably the best-studied rocky planet,” says co-author Aaron Bello-Alfé, an astrophysicist at the Jet Propulsion Laboratory (JPL) in Pasadena, California. Its parent star shines brightly in the night sky and is large for a rocky planet, making it easier to study than other planets outside our solar system. “Every conceivable telescope or astronomical instrument has aimed at this planet at some point,” Bello-Alfé says. 55 Cancri was so well studied that after his JWST launched in December 2021, engineers aimed the observatory’s infrared spectrometer at it for a test. These instruments absorb infrared wavelengths from starlight, allowing them to detect the chemical fingerprints of the gas swirling around the planet. So Belloalfe and his colleagues decided to drill deeper to see if the planet had an atmosphere. Before the latest observations, astronomers had changed their minds about 55 times. This planet was discovered in her year 20042. At first, researchers thought this was probably the core of a gas giant like Jupiter. However, in 2011, when the Spitzer Space Telescope observed the planet passing in front of the star, researchers found that 55 Cancri is actually much smaller and denser than the gas giant. , discovered that it is a rocky super-Earth.

A few years later, researchers found that 55 Cancri e had a lower temperature than expected for a planet so close to its star, suggesting that the planet likely had an atmosphere.4 One hypothesis was that the planet was a “water world,” surrounded by supercritical water molecules. Another was that it was surrounded by a vast primordial atmosphere made up mainly of hydrogen and helium.5 But these ideas were ultimately rejected. If the planet was so close to the star, it would be exposed to stellar winds, which would make it difficult to capture volatile molecules in the atmosphere, says Renyu Hu, a planetary scientist at JPL and co-author of the latest study. That left two options, he says. The first was that the planet was completely dry, with an ultra-thin atmosphere made of evaporated rock. The second reason is that they have a denser atmosphere made up of heavier, more volatile molecules that don’t evaporate easily. clearer image The latest data suggests that 55 Cancri’s atmosphere contains carbon-based gases, suggesting option 2. Seager said the team has collected real evidence of an atmosphere, but further observations are needed to determine its full composition, the relative amounts of gases present, and its exact thickness. Laura Schaefer, a planetary geologist at Stanford University in California, wants to understand how 55 Cancri’s atmosphere interacts with material beneath the planet’s surface. The atmosphere could still be eroded by stellar winds, but the gas could be replenished by melting rocks in the magma ocean and outgassing, the study authors said. “Earth is probably going through at least one magma ocean stage, and possibly multiple stages,” Schaefer says. “Today’s examples of magma oceans help us understand the early history of our solar system.”

source: doi: https://doi.org/10.1038/d41586-024-01332-w