WASP-121b is one of the hottest WASP planets, since it is fiercely irradiated by being in a very tight orbit of only 1.27 days around a hot F star. The Hubble spectra show clear absorption features caused by metals including Magnesium and Iron:
“Heavy metals have been seen in other hot Jupiters before, but only in the lower atmosphere,” explains David Sing, “So you don’t know if they are escaping or not. With WASP-121b, we see magnesium and iron gas so far away from the planet that they’re not gravitationally bound.”
“The heavy metals are escaping partly because the planet is so big and puffy that its gravity is relatively weak. This is a planet being actively stripped of its atmosphere.”
The Hubble press release continues: “This exoplanet is also a perfect target for NASA’s upcoming James Webb Space Telescope to search in infrared light for water and carbon dioxide, which can be detected at longer, redder wavelengths. The combination of Hubble and Webb observations would give astronomers a more complete inventory of the chemical elements that make up the planet’s atmosphere.”
STSci have produced an artist’s impression of WASP-121b, showing how the planet’s shape is tidally distorted by the gravity of the star that it orbits:
The press release has led to coverage on over 50 news and science websites, including Newsweek, CNN, Fox News, Metro, The Daily Mail, The Express, and countries including Switzerland, Germany, India, and Malaysia.