Astronomers have spotted strange signals on giant exoplanets that are "raining iron."

Last year, astronomers discovered a strange nocturnal phenomenon on WASP-76b, a "hot Jupiter" about 640 light-years from Earth. Every night, there will be "iron rain" on the planet.

The reason for the "iron rain" is a lot of heat. The exoplanet is tidally locked onto its parent star, meaning it only shows one side to its hot "companions." In early 2020, researchers estimated that the planet could be warming up to about 2100 degrees Celsius, enough to vaporize metals such as iron.

According to a new study published Sept. 28 in the Astrophysical Journal Newsletter, astronomers used the Hawaii Gemini Telescope to observe the planet from Earth. Through a technique called spectroscopy that allows scientists to detect elements based on characteristic light signals, the researchers analyzed wasp-76b's upper atmosphere and unexpectedly found that it contained a strong spectral signal of ionized calcium.

Ernst de Mooij, an astrophysicist at Queen's University Belfast and co-author of the study, said: "We see signals from calcium, which comes from the planet's fragile upper atmosphere, which is much stronger than we expected from the model. ”

Since the planet is so far away, it is currently impossible to see exactly what is causing the presence of calcium in large quantities. Astronomers don't have telescopes powerful enough to observe WASP-76b, but the new information does begin to help astronomers unravel what's really going on in the world 640 light-years away.

Previous studies have looked at two other massive, hot exoplanets, ionized calcium on KELT-9b and WASP-33b. The team notes that these super-hot Jupiter models are inconsistent with the calcium signals they saw, suggesting that an unknown process may have carried calcium higher in the atmosphere. The new study, in line with the study, could help astronomers study how gases and elements escape into space in the atmosphere.

These results form part of an exo planet atmosphere survey known as ExoGemS, which uses the Hawaiian Gemini Telescope. The program will use the same technique on other exoplanets and shed more light on their diversity, and wasp-76b's strange calcium signal will inform the next series of exoplanet analyses.

"We are planning to observe a large number of exoplanet samples over a range of mass and temperature ranges to explore the diversity of exoplanet atmospheres and help us better understand fundamental processes," de Mooij said. ”