‘Inferno-like’ planet so hot it rains iron is even hotter than astronomers thought

The planet is approximately the size of Jupiter and located 640 light-years from Earth, reaching temperatures of 2426 degrees Celsius

(ESO/M. Kornmesser)

Scientists have discovered that a planet so scorching that it rains iron is even hotter than they previously thought.

The ‘inferno-like’ WASP-76b exoplanet was discovered in 2016, approximately the size of Jupiter and 640 light-years from Earth. The planet is so close to its star that it completes an orbit in just under two Earth days.

WASP-76b’s rapid orbit is also tidally locked, meaning that one size always faces the star. This gives the planet a temperature of 1315 degrees Celsius on its ‘cool’ side, and an incredible 2426 degrees Celsius on the other.

The planet is hot enough that molecules are turned into atoms and metal iron is turned into vapour. Winds then carry this vapour from the hot side of the planet to the cool side where it condenses into icon clouds.

Recently, however, scientists at Cornell University in Toronto and Queen’s University Belfast reported the discovery of ionized calcium on the planet. “We’re seeing so much calcium; it’s a really strong feature,” first author of the research Emily Deibert said.

“This spectral signature of ionized calcium could indicate that the exoplanet has very strong upper atmosphere winds. Or the atmospheric temperature on the exoplanet is much higher than we thought.

“The exoplanet moves fast on its orbit and that’s how we were able to separate its signal from starlight,” she said. “You can see that the calcium imprint on the spectra is moving quickly along with the planet.”

This finding is the first in a multi-year research project to explore the diversity of planetary atmospheres, in order to “develop a more complete picture of the true diversity of alien worlds – from those hot enough to harbour iron rain to others with more moderate climates, from those heftier than Jupiter to others not much bigger than the Earth,” Ray Jayawardhana, the Harold Tanner Dean of the College of Arts and Sciences (A&S), and a professor of astronomy, said.

“It’s remarkable that with today’s telescopes and instruments, we can already learn so much about the atmospheres – their constituents, physical properties, presence of clouds and even large-scale wind patterns – of planets that are orbiting stars hundreds of light-years away.”