In a world almost 640 light-years from Earth, liquid iron falls from the sky like rain. And scientists now report that the extreme atmosphere may be hotter than previously thought.
WASP-76b is a fiery gas giant exoplanet discovered in 2016. It’s dubbed an “ultra-hot Jupiter” because it’s close to the star it orbits.
As a “tidally locked” planet, one side of WASP-76b always faces the sun – so average temperatures range from 2,400 degrees Fahrenheit on its permanent night half to 4,400 degrees on its permanent day half. To put that in perspective, the hottest planet in our solar system, Venus, has an average temperature of 880 degrees, according to NASA. Earth’s average temperature is 61 degrees.
The fiery exoplanet WASP – 76b may be hotter than previously thought. ESO/M.Kornmesser
Amid the scorching climate, WASP-76b is famous for its iron rain – resulting from iron vaporizing on the day side, then condensing on the night side to shower the planet. And, if this weather wasn’t extreme enough, researchers have detected ionized calcium in the atmosphere.
In a Sept. 28 report published in the peer-reviewed scientific journal The Astrophysical Journal Letters, an international team of scientists suggest that the discovery could mean WASP-76b’s climate is even more intense than expected.
“It’s already quite an extreme and exotic type of atmosphere. A world unlike any in our own solar system,” report co-author Ray Jayawardhana, Harold Tanner Dean of the College of Arts and Sciences at Cornell University and a professor of astronomy, told USA TODAY. “Our detection of ionized calcium suggests that upper layers of the atmosphere may be even hotter than previously known. And/or it might also include large scale winds … In some ways, the conditions in the upper atmosphere of a planet like this may not be that different from that of a red dwarf star.”
In addition to discovering ionized calcium in WASP-76b’s atmosphere, the team also confirmed the presence of previously detected sodium. Their research is part of a Cornell University-led project named ExoGemS, or Exoplanets with Gemini Spectroscopy survey.
The results published in last month’s report were the first that the team detected with observations from the Gemini North Telescope, near the summit of Mauna Kea in Hawaii. According to Jayawardhana, the team plans to observe dozens of exoplanets, with a range of masses and temperatures, using the Gemini North in the coming years. Similar work will be done with the James Webb Space Telescope, which is set to launch in December.
“One thing that’s quite stunning is the fact that these planets that are literally hundreds of light-years away, (but) here we are using a telescope on the ground on Earth,” Jayawardhana said. “We’re able to do remote sensing across hundreds of light years, and actually measure – not just theorize, not just speculate – but actually measure constituents and conditions on alien worlds.”
Jayawardhana added that exponentially more breakthroughs could be coming, especially when reflecting on how far research has already come since the first exoplanets were discovered in the 1990s. He hopes that the observations today are a preview of what the next generation of telescopes, on Earth and in space, will be exploring – for a wide range of planets, not just the ultra-hot Jupiters.
“The coming few years will continue to be an incredibly exciting time for those of us interested in worlds beyond our own solar system … (It will) probably not only expand our understanding of the cosmos, but also bring us a few surprises that we haven’t anticipated.”