Scientists find planet where it 'rains iron' at night

11 March 2020, 23:40

Wasp-76b has such extreme temperatures it is thought to rain iron
Wasp-76b has such extreme temperatures it is thought to rain iron. Picture: European Southern Observatory

By Tobi Akingbade

Astronomers have discovered a distant planet where it is thought to rain iron.

Wasp-76b - as it has been called - has permanent daytime, and is blighted by temperatures of up to 2,400 degrees Celsius.

The strange planet orbits so close to its host star weather that the extreme weather causes metals on the surface evaporate.

But at nighttime, the planet cools to a not-so chilly 1,400 degrees Celsius, allowing those metals to condense and rain out as droplets of iron that the drop over the surface.

"One could say that this planet gets rainy in the evening, except it rains iron," says David Ehrenreich, a professor at the University of Geneva in Switzerland, who led the study that found the exoplanet outside of the solar system.

Wasp-76b is 640 lightyears away, in the Pisces constellation.

It is so close to its host star that temperatures reach up to 2,400C during the day
It is so close to its host star that temperatures reach up to 2,400C during the day. Picture: European Southern Observatory

The Swiss researcher and colleagues have just published their findings on this strange place in the journal Nature.

Wasp-76b is a monster gas planet that's twice the width of our solar system's Jupiter.

Its unique was inspired by the UK-led Wasp telescope system that detected the world four years ago.

The team describes how it used the new Espresso instrument at the European Southern Observatory's Very Large Telescope in Chile to study the chemistry of Wasp-76b in fine detail.

Another of the planet's unique features is that it always presents the same face to the star. This, something Earth’s Moon also does, means the planet is described as "tidally locked".

The scientists detected a strong iron vapour signature at the evening frontier, or terminator, where the day on Wasp-76b transitions to night.

But when the researchers spotted the morning transition, the iron signal was no longer there.

Dr Ehrenreich explained: "What we surmise is that the iron is condensing on the nightside, which, although still hot at 1,400C, is cold enough that iron can condense as clouds, as rain, possibly as droplets.

“These could then fall into the deeper layers of the atmosphere which we can't access with our instrument."