PLANET DIO

"In addition to being a gas giant without a solid surface, Kelt-9b lies hundreds of light-years away and is the hottest planet ever observed. Temperatures on its outer layer can exceed 4,000 degrees Celsius (7,000 degrees Fahrenheit) — hotter than some stars — and a new study shows that its superheated atmosphere contains vaporized heavy metals."

And if the temperatures fall low enough, the metal atoms in the atmosphere might link to form molecules and then coalesce into particles that would sink into the planet's interior. "Just like clouds on Earth drop liquid water raindrops, the rain on the night side would be iron drops," Seager said, adding that the drops would be very dense.

But what would iron rain be like? Jens Hoeijmakers, the study's lead author, offered an analogy: "If you want to imagine it, raining lava might get you close!"