Astronomers find curious signal on hot, raining iron planet

If you haven’t heard of WASP-76b, sorry to tell you, but you missed something. Last year, astronomers revealed that “Hot Jupiter,” which is about 640 light years from Earth, has a curious nocturnal quirk. Every night on the planet it’s raining iron. Yes, the elements that go into building our skyscrapers and apartments literally fall from the sky on WASP-76b.

The reason for the iron rain is the intense heat. The exoplanet is locked by the tide on its mother star, meaning it only ever shows one side of its burning companion and its face is constantly on fire. In early 2020, researchers estimated the planet had likely reached around 3,800 degrees Fahrenheit (or around 2,100 degrees Celsius), enough to vaporize metals like iron.

But, for those looking to upgrade to WASP-76b, the estimates may have been a bit low.

A new study, published Sept. 28 in the Astrophysical Journal Letters, used the Hawaiian Gemini telescopes to examine the planet from Earth. Using a technique known as spectroscopy, which allows scientists to detect elements based on a characteristic light signature, the researchers analyzed the upper atmosphere of WASP-76b and, unexpectedly, found that it contained the strong spectral signal of ionized calcium.

“The signal we are seeing from calcium, which comes from the planet’s thin upper atmosphere, is much stronger than what we expect from models,” said Ernst de Mooij, an astrophysicist at Queen’s University in Belfast and co- author of the study.

Because the planet is so far away, it is not possible at this time to see exactly what is causing the abundance of calcium. We don’t have telescopes powerful enough to visualize what’s going on at WASP-76b, but the new information is starting to help astronomers unravel exactly what’s going on in a world 640 light years away.

Previous research had looked at ionized calcium on two other giant, hot exoplanets known as KELT-9b and WASP-33b. This research team noted that the patterns of these super hot Jupiters did not match the calcium signal they were seeing, suggesting that an unknown process could be driving calcium higher in the atmosphere. The new study aligns with that research and could help astronomers study the atmospheric leak of gases and elements into space – something that happens much faster if you’re right next to your host star and warm enough. to vaporize the iron.

The findings are part of a survey of exoplanet atmospheres known as ExoGemS, which uses the Hawaiian Gemini Observatory. The program will use the same technique on other exoplanets and report more on their diversity, with the curious calcium in WASP-76b informing the next round of exoplanet analyzes.

“We plan to observe a large sample of exoplanets over a range of masses and temperatures to explore the diversity of exoplanet atmospheres and help us better understand the underlying processes,” said de Mooij.