Researchers have found the "weird" exoplanet WASP-79b, nearly 800 light-years from Earth, does not have a blue sky as our planet does. Instead, its skies are yellow.
According to a statement from NASA, WASP-79b orbits its host star once every 3.7 Earth days and is not in the habitable zone, the proximity of which a planet is to a star where it could support liquid water.
The exoplanet, known as a "hot Jupiter," also does not have any evidence of Rayleigh scattering, which is what causes Earth's skies to appear blue by "scattering the shorter (bluer) wavelengths of sunlight," the agency noted. That's left experts puzzled.
"This is a strong indication of an unknown atmospheric process that we're just not accounting for in our physical models," said researcher Kristin Showalter Sotzen of the Johns Hopkins University in a statement. "I've shown the WASP-79b spectrum to a number of colleagues, and their consensus is 'that's weird.'"
In addition to having a yellow sky, WASP-79b is exceptionally hot, with an average temperature of approximately 3,000 degrees Fahrenheit, making it one of the largest exoplanets ever observed.
"WASP-79b is twice the mass of Jupiter and is so hot it has an extended atmosphere, which is ideal for studying starlight that is filtered through and grazes the atmosphere on its way toward Earth," NASA added.
The exoplanet is 780 light-years from Earth in the constellation Eridanus. A light-year, which measures distance in space, equals 6 trillion miles.
WASP-79b may also have "scattered clouds, and iron lifted to high altitudes could precipitate as rain," the agency explained.
Researchers also discovered that another exoplanet, WASP 76-b, is believed to have "iron rain."
Sotzen added that the researchers are not really sure what's causing the phenomena, as it's the first time they've seen this.
"We need to keep an eye out for other planets like this because it could be indicative of unknown atmospheric processes that we don't currently understand," Sotzen explained. "Because we only have one planet as an example, we don't know if it's an atmospheric phenomenon linked to the evolution of the planet."
The findings were published in the Astronomical Journal.