The exoplanet WASP-76b is even more extreme than it appeared

Artist's concept of iron rain on the exoplanet WASP-76b (Image ESO/M. Kornmesser)
Artist’s concept of iron rain on the exoplanet WASP-76b (Image ESO/M. Kornmesser)

An article published in “The Astrophysical Journal Letters” reports a study on the exoplanet WASP-76b, an ultra-hot Jupiter where conditions could be even more hellish than previously thought. A team of researchers used the Gemini North telescope to study WASP-76b, the case that inaugurates a planetary atmosphere mapping project at Cornell University as part of ExoGemS (Exoplanets with Gemini Spectroscopy Survey). The discovery of abundant ionized calcium indicates that the temperature in the atmosphere is much higher than previous estimates or that there are very intense winds in the upper atmosphere.

About 640 light-years from Earth, the exoplanet WASP-76b was discovered in 2013 around a star with a mass nearly 1.5 times the Sun’s and a diameter about 1.7 times the Sun’s. WASP-76b has a mass slightly lower than Jupiter’s but its size is almost twice Jupiter’s because it’s “inflated” by the heat. In fact, it’s close to its star, about 5 million kilometers from it, to the point that its year lasts about 1.8 Earth days and one consequence is that it receives an enormous amount of heat. Gas giant planets with such characteristics are called hot Jupiters. An article published in March 2020 in the journal “Nature” reported the iron rains occurring on WASP-76b.

The new study on the exoplanet WASP-76b was conducted using in particular the GRACES (Gemini Remote Access to Cfht Espadons Spectrograph) instrument mounted on the Gemini North telescope in Hawaii. This made it possible to examine the characteristics of the exoplanet WASP-76b’s atmosphere thanks to the traces left by various elements and chemical compounds in its electromagnetic emissions. The result was the detection of a significant presence of ionized calcium.

Emily Deibert of the University of Toronto, the first author of the article, explained that the exoplanet WASP-76b moves quickly in its orbit and that’s why it was possible to separate its signal from its star’s showing how the trace of ionized calcium followed the planet’s movement. Regarding the presence of ionized calcium, she stated that it could indicate that the exoplanet WASP-76b has very strong winds in the upper atmosphere or that the atmospheric temperature on the planet is much higher than previously thought.

Ray Jayawardhana, professor of astronomy at Cornell University and one of the authors of the study, explained the importance of the ExoGemS survey, of which the examination of the atmosphere of the exoplanet WASP-76b represents the first result. This multi-year investigation will allow developing a more complete picture of the real diversity of alien worlds, from the most extreme to the most temperate ones.

The researchers also intend to continue the study of the exoplanet WASP-76b, which is turning out to be even more extreme than the research published in 2020 showed. This exoplanet is a sort of cosmic laboratory where physical and chemical processes take place that are difficult to find elsewhere, and for this reason, arouses a lot of curiosity.

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