Thanks to the James Webb Space Telescope, astronomers have discovered a scorching hot lava planet composed of diamond that has developed a second atmosphere after its host star destroyed its original one.
55 Cancri e, named after one of the five planets orbiting the star 55 Cancri in the Cancer constellation, has a diameter twice that of Earth but a mass up to eight times greater. It completes a full orbit around its star in just 18 hours, which is significantly shorter than Earth’s 365-day orbit, and is extremely hot.
The star 55 Cancri and its five planets are located about 40 light-years away from Earth and were discovered in 2004. Humans can see 55 Cancri with the naked eye during the evening.
Illustration of the structure of the planet 55 Cancri e. It is covered by a layer of graphite. Diamond constitutes the next layer (in white). Silicon-containing minerals (in gray) form the layer beneath the diamond layer. The core of the planet is a massive iron block (in orange). (Photo: Space).
After analyzing the mass, diameter of the planets, and the composition of the star, scientists from Yale University in the U.S. concluded that the main component of 55 Cancri e is carbon (diamond or graphite). It also contains iron, silicon carbide, and even silicates. Pure diamond makes up at least one-third of the planet’s mass, according to Space.
“This is a rocky planet with a completely different chemical composition than Earth. Its surface is likely covered in graphite and diamond, rather than water and granite like our planet,” stated Nikku Madhusudhan, the lead researcher.
55 Cancri e is classified as a Super-Earth, meaning it has a larger mass than Earth but is lighter than Neptune and Uranus.
This exoplanet is so dense that astronomers hypothesize it is primarily composed of carbon compressed into diamond. The planet orbits its host star 55 Cancri A at a distance of 2.3 million kilometers, which is 0.01544 times the distance between Earth and the Sun. This proximity means that 55 Cancri e takes only about 17 Earth hours to complete one orbit around its host star, with a surface temperature of approximately 2,400 degrees Celsius.
Radiation from the host star caused 55 Cancri e to lose its original atmosphere, similar to other rocky planets orbiting their stars at too close a distance. However, a study published on May 8 in the journal Nature revealed a thick layer of gas surrounding the planet, indicating that it has developed a second atmosphere. According to Renyu Hu, a researcher at the California Institute of Technology (Caltech), this atmosphere could be supported by gases escaping from the rocky layer beneath 55 Cancri e. In 2016, the Hubble Space Telescope identified that the atmosphere of 55 Cancri e contains hydrogen and helium.
Planet 55 Cancri e orbits very close to its scorching hot host star – (Graphic: NASA/ESA/CSA/STScl)
There are two plausible scenarios that could explain the atmosphere of 55 Cancri e. First, the Super-Earth could be a lava world with a thin silicate atmosphere that evaporates. This atmosphere could consist of volatile chemical compounds containing carbon, nitrogen, hydrogen, and sulfur, which may be lost due to radiation from the host star. The other possibility is that the planet has a thick secondary atmosphere formed over time through volcanic activity. To determine which scenario is correct, Hu and his team are examining observations from the James Webb Space Telescope as the planet passes behind its host star, 55 Cancri A. The data rules out the first possibility, suggesting that molten lava has helped 55 Cancri e develop a second atmosphere.
“55 Cancri e is so close to its host star that it receives a lot of heat in the form of radiation, keeping the temperature on the planet consistently high. At these temperatures, everything on the planet is molten. The process of gas escape from the molten rock supports the formation of a second atmosphere,” Hu explains.
According to Hu, the original atmosphere of 55 Cancri e primarily consisted of hydrogen and helium. However, the research team is uncertain about the composition of the second atmosphere. While observations from the Webb telescope did not provide conclusive answers, models used to interpret the measurement results indicate a significant presence of carbon dioxide and carbon monoxide.
