The fiery, hell-like WASP-76b exoplanet, which is considered an ultra-hot Jupiter - a place where iron is vaporized, condenses on the night side, and then falls from the sky like rain - could be even hotter than scientists thought.

Ionized calcium has been discovered on the planet, according to an international team led by scientists from Cornell University, the University of Toronto, and Queen's University Belfast. This suggests a higher atmospheric temperature than previously assumed, or powerful upper atmosphere winds.

High-resolution spectra obtained with Gemini North near the summit of Mauna Kea in Hawaii were used to make the discovery.

Because of their close proximity to their stars, hot Jupiters have high temperatures. WASP-76b, found in 2016, is 640 light-years from Earth yet is so near to its F-type star, which is slightly hotter than the sun, that it completes one orbit every 1.8 Earth days.

"As we do remote sensing of dozens of exoplanets, spanning a range of masses and temperatures, we will develop a more complete picture of the true diversity of alien worlds -- from those hot enough to harbor iron rain to others with more moderate climates, from those heftier than Jupiter to others not much bigger than the Earth," study coauthor Ray Jayawardhana said in a statement.

WASP-76b absorbs thousands of times the amount of solar energy that Earth receives. The planet is tidally locked, which means that the same side of the planet faces the star at all times. Our moon orbits the Earth in a similar manner. Temperatures on the planet's "dayside," which faces the star, top 4,400 degrees Fahrenheit (2,426 degrees Celsius).

Iron vapor is created by the scorching temperatures on the dayside, which are hot enough to convert molecules into atoms and metal into vapor. This is carried over to the nightside, when temperatures are slightly colder, hovering around 2,400 degrees Fahrenheit (1,315 degrees Celsius).

The iron vapor condenses into clouds, resulting in liquid iron rain, which is what causes the iron in the atmosphere.

The study's findings were published in the Astrophysical Journal Letters on Sept. 28 and presented at the American Astronomical Society's Division for Planetary Sciences annual meeting on Tuesday.