Free Astronomy Magazine May-June 2020

23 MAY-JUNE 2020 SPACE CHRONICLES around 1500 degrees Celsius. Not only does WASP-76b have different day-night temperatures, it also has distinct day-night chemistry, accord- ing to the new study. Using the new ESPRESSO instrument on ESO’s VLT in the Chilean Atacama Desert, the astronomers identified for the first time chemical variations on an ultra- hot gas giant planet. They detected a strong signature of iron vapour at the evening border that separates the planet’s day side from its night side. “Surprisingly, however, we do not see the iron vapour in the morning,” says Ehren- reich. The reason, he says, is that “it is raining iron on the night side of this extreme exoplanet.” “The observations show that iron vapour is abundant in the atmos- phere of the hot day side of WASP- 76b,” adds María Rosa Zapatero Osorio, an astrophysicist at the Centre for Astrobiology in Madrid, Spain, and the chair of the ESPRESSO science team. “A fraction of this iron is injected into the night side owing to the planet’s ro- tation and atmospheric winds. There, the iron encounters much cooler environments, condenses and rains down.” This result was obtained from the very first science observations done with ESPRESSO, in September 2018, by the scientific consortium who built the instrument: a team from Portugal, Italy, Switzerland, Spain and ESO. ESPRESSO — the Echelle SPectro- graph for Rocky Exoplanets and Sta- ble Spectroscopic Observations — was originally designed to hunt for Earth-like planets around Sun-like stars. However, it has proven to be much more versatile. “We soon re- alised that the remarkable collecting power of the VLT and the extreme stability of ESPRESSO made it a prime machine to study exoplanet atmospheres,” says Pedro Figueira, ESPRESSO instrument scientist at ESO in Chile. “What we have now is a whole new way to trace the cli- mate of the most extreme exoplan- ets,” concludes Ehrenreich. T he ultra-hot giant exoplanet WASP-76b orbits the star WASP-76, located some 390 light-years away in the constellation of Pisces. This video shows the orbit of this strange planet around its host star. [ESO/L.Calçada /spaceengine.org ] !