A Planet Hot Enough To Vaporize Iron Looks To Be Even Hotter - Forbes

When astronomers first discovered and described the exoplanet WASP-76b, it seemed beyond hellish: a gas giant so hot that iron doesn’t just melts but gets vaporized, only to condense on the night side of the planet and fall as a sort of molten metal rain.

Now new observations suggest this horrid inferno globe could be even hotter than all that — much hotter.

A team of researchers with leaders from University of Toronto, Cornell, and Queen’s University Belfast used Cornell’s Exoplanets with Gemini Spectroscopy survey, or ExoGemS, to identify the presence of ionized or “free” calcium in the planet’s atmosphere.

“We’re seeing so much calcium, it’s a really strong feature,” said Emily Deibert, a doctoral student at University of Toronto. “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.”

This illustration shows a night-side view of the exoplanet WASP-76b. The ultra-hot giant exoplanet ... [+] has a day side where temperatures climb above 2400 degrees Celsius, high enough to vaporise metals. Strong winds carry iron vapour to the cooler night side where it condenses into iron droplets. To the left of the image, we see the evening border of the exoplanet, where it transitions from day to night.

ESO/M. Kornmesser

Deibert is the first author on a paper published in the Astrophysical Journal Letters that’s also being presented Tuesday at the annual meeting of the Division for Planetary Sciences of the American Astronomical Society.

WASP-76b is unlike any planet in our solar system, although astronomers have discovered a fair amount of so-called “hot Jupiters” like it around more distant stars. The large planet orbits very closely to its F-type star, which is slightly hotter than our sun, completing a trip around it every 1.8 Earth days.

The planet is also tidally locked so the same side is always facing its star, much the same way the moon always shows the same side to the Earth. The sun-facing side of WASP-76b swells outward as its temperatures soar above 4,400 degrees Fahrenheit. Its night side is a comparatively balmy 2,400 degrees F.

Deibert says investigating such wild worlds, which are a bit easier to spot due to their size and close-in orbit, will eventually help astronomers take closer looks at more hospitable places.

“The insights we gain from these observations will help us to one day be able to study the atmospheres of Earth-like worlds.”

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