Diamond exoplanet lost atmosphere and created another

Using the James Webb Space Telescope (JWST), astronomers have discovered that a scorching hot lava planet, believed to be composed of diamond, has developed a second atmosphere after having the first destroyed by the star it orbits. This is the conclusion of a study published this Wednesday (8) in the journal Nature.

Named 55 Cancri e (we already talked about it here), this exoplanet is located almost 41 light-years from the Solar System. Its width is almost twice that of Earth and its mass is approximately nine times that of our planet.

It is categorized as a “super-Earth”, a designation that indicates a greater density compared to Earth and lower when compared to gas giants such as Neptune and Uranus.

The extraordinary density of 55 Cancrie has led scientists to speculate that it may be predominantly composed of carbon, possibly crystallized into a diamond shape due to intense pressure and heat.

This exoplanet’s proximity to the Sun-like star, 55 Cancri A, is equally remarkable, with it at a distance of 2.3 km from it. This cosmic arrangement results in a rapid orbit, lasting just 17 Earth hours, with a boiling surface temperature of around 2,400ºC.

This short distance between the two bodies led to the loss of 55 Cancri’s original atmosphere and due to intense radiation, a phenomenon observed on other rocky planets orbiting nearby stars. However, analyzes from the new research indicate that the planet has developed a second atmosphere, defying expectations and intriguing the authors.

“We measured the thermal emissions from this rocky planet, and the measurement indicates that the planet has a substantial atmosphere,” revealed Renyu Hu, a member of the research team and researcher at the California Institute of Technology (Caltech), in an interview with Space.com. “This atmosphere is likely sustained by emission of gases from the rocky interior of 55 Cancri e, and we believe this is the first measurement of a secondary atmosphere on a rocky exoplanet. It’s an exciting discovery.”

The exoplanet 55 Cancri e was discovered in 2004, when its presence was detected through oscillations in the motion of the host star, a method known as radial velocity for exoplanet discovery.

Originally named Janssen, this world was the first super-Earth identified orbiting a star that is not in the main sequence phase, that is, a star that still converts hydrogen into helium in its core.

Over the years, detailed observations have revealed not only its fast orbit but also its carbon-rich composition. In 2016, the Hubble Space Telescope deepened our understanding by determining that the atmosphere of 55 Cancri e contained hydrogen and helium, marking the first atmospheric investigation of this exoplanet.

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Why did the diamond world recreate its atmosphere

Two main scenarios can explain the presence of 55 Cancri e’s second atmosphere. The first hypothesis suggests the existence of a thin atmosphere composed of vaporized silicate over a lava surface, while the second theorizes a thick atmosphere developed over time due to volcanism.

To clear up this mystery, Hu and his team examined JWST observations during the secondary eclipse of 55 Cancrie, a crucial event for understanding its atmosphere. The data obtained ruled out the possibility of a bare lava planet, indicating the presence of a substantial atmosphere.

Hu explained that the high temperature keeps the surface molten, allowing gases in the lava to dissolve and the secondary atmosphere to form.

Although the precise details of the composition of the new atmosphere remain a mystery, JWST observations suggest the substantial presence of carbon dioxide and carbon monoxide. This raises fascinating questions about the evolution and diversity of the atmospheres of rocky exoplanets orbiting nearby stars.

55 Cancri is not alone in this class of hot, rocky planets close to their stars. However, its uniqueness in size and orbit stands out, opening new horizons for understanding how planets interact with their stars and develop atmospheres in extreme environments.

The next steps in the investigation of 55 Cancri promise to reveal more secrets about this exotic world and offer valuable insights into planetary diversity beyond our Solar System.