Detection of the atmosphere around a super-hot super-Earth - rts.ch

An international team of astronomers, including Switzerland, was surprised to find clear evidence of an atmosphere around a super-Earth exoplanet, despite the intense heat there. This discovery was made using the James Webb Space Telescope.

“This was completely unexpected,” rejoices Professor Brice Olivier Demory, co-author of this work at the University of Bern. The research team demonstrated that exoplanet 55 Cancri e, located 41 light-years from Earth, can be surrounded by a dense atmosphere despite the high temperature and intense radiation to which it is exposed.

This light curve shows the change in brightness of the 55 Cancri system as rocky planet 55 Cancri e, the closest of the system's five known planets, moves behind its star: a secondary eclipse. When a planet is close to a star, mid-infrared light emitted from both the star and the dayside of the planet reaches the telescope and the system appears brighter. When a planet is behind a star, the light emitted by the planet is blocked and only the star's light reaches the telescope, causing the apparent brightness to decrease. By subtracting the star's brightness from the combined brightness of the star and planet, the amount of infrared light coming from the dayside of the planet can be calculated. This allows one to calculate the temperature on the dayside and conclude whether the planet has an atmosphere. [Illustration: NASA, ESA, CSA, Joseph Olmsted (STScI) - Science: Aaron Bello-Arufe (NASA-JPL)] — This light curve shows the change in brightness of the 55 Cancri system as rocky planet 55 Cancri e, the closest of the system’s five known planets, moves behind its star: a secondary eclipse. When a planet is close to a star, mid-infrared light emitted from both the star and the dayside of the planet reaches the telescope and the system appears brighter. When a planet is behind a star, the light emitted by the planet is blocked and only the star’s light reaches the telescope, causing the apparent brightness to decrease. By subtracting the star’s brightness from the combined brightness of the star and planet, the amount of infrared light coming from the dayside of the planet can be calculated. This allows one to calculate the temperature on the dayside and conclude whether the planet has an atmosphere. [Illustration: NASA, ESA, CSA, Joseph Olmsted (STScI) – Science: Aaron Bello-Arufe (NASA-JPL)]

It is one of five known planets orbiting a Sun-like star in the constellation Cancer. With a diameter almost twice that of Earth and slightly higher density, the planet is a super-Earth: larger than Earth and smaller than Neptune, and similar in composition to the rocky planets of our solar system.

Lava sea

At temperatures around 1700 degrees, gases usually evaporate quickly. However, previous research has shown that heat spreads throughout the planet, which typically indicates the presence of an atmosphere.

The thermal emission spectrum shows the brightness (y-axis) of different wavelengths of infrared light (x-axis) emitted by super-Earth exoplanet 55 Cancri e. This spectrum suggests that the planet may be surrounded not only by vaporized rocks, but likely also by an atmosphere rich in carbon dioxide or monoxide, as well as other volatile elements. The chart compares data collected by NIRCam (orange dots) and MIRI (purple dots) with two different models. Model A (red) shows what the emission spectrum of 55 Cancri e would look like if its atmosphere consisted of vaporized rocks. Model B (blue) shows what the emission spectrum would look like if the planet had a volatile-rich atmosphere degassed from an ocean of magma with volatile content similar to that of Earth's mantle. The MIRI and NIRCam data are consistent with a high-volatile model. [Illustration: NASA, ESA, CSA, Ralf Crawford (STScI) - Science: Renyu Hu (JPL), Aaron Bello-Arufe (JPL), Diana Dragomir (Uni of New Mexico)] — The thermal emission spectrum shows the brightness (y-axis) of different wavelengths of infrared light (x-axis) emitted by super-Earth exoplanet 55 Cancri e. This spectrum suggests that the planet may be surrounded not only by vaporized rocks, but likely also by an atmosphere rich in carbon dioxide or monoxide, as well as other volatile elements. The chart compares data collected by NIRCam (orange dots) and MIRI (purple dots) with two different models. Model A (red) shows what the emission spectrum of 55 Cancri e would look like if its atmosphere consisted of vaporized rocks. Model B (blue) shows what the emission spectrum would look like if the planet had a volatile-rich atmosphere degassed from an ocean of magma with volatile content similar to that of Earth’s mantle. The MIRI and NIRCam data are consistent with a high-volatile model. [Illustration: NASA, ESA, CSA, Ralf Crawford (STScI) – Science: Renyu Hu (JPL), Aaron Bello-Arufe (JPL), Diana Dragomir (Uni of New Mexico)]

This exoplanet was discovered 20 years ago. It orbits so close to its star (one year of its existence lasts just 18 hours) that its surface must melt to form a deep, roiling ocean of magma. Scientists now speculate that this lava may have released enough gas to maintain an atmosphere despite the heat.

The team believes that the gases covering 55 Cancri e are bubbling from the inside. The primary atmosphere would have disappeared long ago due to the star’s high temperature and intense radiation. Consequently, it will be a secondary atmosphere, constantly renewed by an ocean of magma. Magma is not only made up of crystals and liquid rocks, it also contains many dissolved gases.

Better understand our solar system

“These discoveries are also important for us,” notes Brice-Olivier Demory, who has been studying planet 55 Cancri e since the beginning of his career: “This type of super-Earth planet is relatively common, but in our solar system.”

“If we learn more about super-Earths in other solar systems, we will get closer to the hitherto unexplained question of why this is so,” the astrophysicist emphasizes. “So it’s a matter of better understanding our solar system and therefore our origins.”

>> Read also: Astrophysicist Gianfranco Bertone deciphers “unexpected space”

Although it is too hot to be habitable, 55 Cancri e could provide a unique opportunity to study the interactions between the atmospheres, surfaces and interiors of rocky planets and possibly provide information about the origins of Earth, Venus and Mars, which may also have been covered magma.

Now scientists want to take similar measurements on more distant rocky planets to learn more. Their study was published Wednesday in the journal Nature.

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