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'Diamond planet' 55 Cancri e has signs of an atmosphere

An exoplanet orbiting a sun-like star in the constellation Cancer known as 55 Cancri e stands out as a fascinating celestial body.

The exoplanet is classified as a super-Earth due to its size, which is nearly twice the diameter of our planet and slightly denser. It bridges the gap between Earth and Neptune in terms of size and composition.

These features make it a prime candidate for in-depth astronomical studies, particularly to understand its atmospheric properties.

Pioneering discoveries and new insights

Recently, new details about 55 Cancri e have emerged through collaborative efforts involving advanced space telescopes. A key figure in this research is Dr. Brice-Olivier Demory from the Center for Space and Habitability (CSH) and the NCCR PlanetS.

“55 Cancri e is one of the most enigmatic exoplanets. Despite enormous amounts of observing time obtained with a dozen of ground and space facilities in the past decade, its very nature has remained elusive, until today, when parts of the puzzle could finally be put together thanks to the James Webb Space Telescope (JWST),” noted Dr. Demory.

The JWST has demonstrated potential in studying hot, highly irradiated rocky planets and may soon provide insights into cooler, potentially habitable worlds.

Renyu Hu of NASA’s Jet Propulsion Laboratory (JPL) emphasized the telescope’s impact. “JWST is really pushing the frontiers of exoplanet characterization to rocky exoplanets. It is truly enabling a new type of science.”

The role of CHEOPS

Furthering our understanding, the CHEOPS space telescope, which was developed and built at the University of Bern, has been instrumental in answering several key questions about 55 Cancri e.

Observations from both CHEOPS and JWST suggest that 55 Cancri e may host an atmosphere containing gases like carbon monoxide or carbon dioxide.

The climate of a super-hot super-Earth exoplanet

Despite its rocky composition, the exoplanet 55 Cancri e presents conditions far from those found on Earth. The planet’s proximity to its star creates extreme surface temperatures likely leading to a molten magma ocean.

“The planet is so hot that some of the molten rock should evaporate,” noted Hu. This proximity also suggests that 55 Cancri e is tidally locked, maintaining a constant day side facing the star and a night side in perpetual darkness.

Innovative observational techniques

The research team utilized the JWST’s NIRCam and MIRI to observe infrared light from 55 Cancri e, allowing them to deduce surface temperatures and atmospheric characteristics.

By comparing the light emitted during the planet’s secondary eclipse (when it is behind its star) with its normal state, the experts determined that the dayside temperature is cooler than expected if the planet had no atmosphere.

This temperature discrepancy suggests a volatile-rich atmosphere that distributes energy from the day to the night side, challenging previous assumptions about heat distribution solely by lava flows.

A window into exoplanet development

The potential atmosphere around the exoplanet 55 Cancri e, as recently analyzed by scientists from Stanford University and Colorado State University, likely stems from the planet’s bubbling magma ocean. Consequently, this suggests a secondary atmosphere continuously replenished by volcanic activity.

The research has provided a unique opportunity to study the interactions between planetary atmospheres, surfaces, and interiors. These insights are possibly applicable to the early stages of Earth, Venus, and Mars.

“Ultimately, we want to understand what conditions make it possible for a rocky planet to sustain a gas-rich atmosphere: the key ingredient for a habitable planet,” said Hu.

While 55 Cancri e is not habitable, it provides a valuable laboratory for studying extreme planetary environments and their atmospheres. These insights deepen our understanding of distant worlds and advance our quest to find life-sustaining conditions elsewhere.

More about 55 Cancri e 

55 Cancri e is located about 40 light years away from Earth in the constellation Cancer. It’s notable for being one of the first discovered exoplanets that orbits a main sequence star similar to our Sun. 

This planet is extremely close to its star, 55 Cancri, with an orbit so tight that a year there lasts just about 18 hours. This proximity leads to incredibly high surface temperatures, potentially reaching up to 2,700 degrees Celsius, making it unlikely to support life as we know it. Additionally, the planet could have an atmosphere denser than Earth’s, possibly rich in hydrogen and helium.

There’s also speculation, based on its density and the emissions observed, that 55 Cancri e could have a substantial amount of carbon in its composition. Some scientists hypothesize that a large part of this carbon might be in the form of diamond, leading to the nickname “diamond planet.” 

However, these are still subjects of ongoing research and debate in the scientific community. The planet presents a rich field of study that could help us understand more about planet formation and the characteristics of planets outside our solar system.

The study is published in the journal Nature.


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