Scientists Discover New Planet Where It Rains Iron

by : Emily Brown on : 11 Mar 2020 17:44
Scientists Discover New Planet Where It Rains IronEuropean Southern Observatory/M. Kornmesser

Scientists have discovered a distant planet with temperatures so hot it causes iron to rain from the sky.

The planet, known as Wasp-76b, is located 390 light-years from Earth, though scientists were able to study its chemistry in fine detail using the new Espresso instrument on European Southern Observatory’s Very Large Telescope in Chile.


On one side of the planet it is permanently daytime, and temperatures there exceed 2,400°C due to the planet’s proximity to its host star. The other side of the planet, where it is permanently night, is around 1,000°C cooler.


Dr David Ehrenreich, from the University of Geneva, told the BBC the environment is ‘bizarre’ as the conditions mean that instead of ‘a drizzle of water droplets, you have iron droplets splashing down’.

The planet’s dayside temperatures are hot enough to vaporise metals on the surface, which are then carried by strong winds over to the other side of the planet. There, it is cool enough for the metals to condense and rain down.


Ehrenreich and his colleagues published their findings in the journal Nature, explaining that one interesting feature of the planet is the fact that, like our moon, it always presents the same face to its host star – a behaviour scientists call being ‘tidally locked’.


As a result, the dayside of the planet is being roasted, to the point where researchers suggest all clouds are dispersed and all molecules in the atmosphere are broken apart into individual atoms.

The team believe the extreme temperature difference between each side of the planet produce ferocious winds, blowing up to 18,000km/h.


Using the Espresso spectrometer, the scientists detected a strong iron vapour signature at the evening frontier – where the day on Wasp-76b transitions to night. However, when the group observed the morning transition, the iron signal was gone.

Ehrenreich explained:

What we surmise is that the iron is condensing on the nightside, which, although still hot at 1,400°C, 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.


Another of the scientists, Prof Don Pollacco from Warwick University, told the BBC the strange environment is hard to comprehend.

He commented:

This thing orbits so close to its star, it’s essentially dancing in the outer atmosphere of that star and being subjected to all kinds of physics that, to put it bluntly, we don’t really understand.

It will either end up in the star or the radiation field from the star will blow away the planet’s atmosphere to leave just a hot, rocky core.


Wasp-76b gets its unusual name from the UK-led Wasp telescope system that detected the world four years ago.

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Emily Brown

Emily Brown first began delivering important news stories aged just 13, when she launched her career with a paper round. She graduated with a BA Hons in English Language in the Media from Lancaster University, and went on to become a freelance writer and blogger. Emily contributed to The Sunday Times Travel Magazine and Student Problems before becoming a journalist at UNILAD, where she works on breaking news as well as longer form features.

Topics: Science, Astronomy, planet, Space, universe


Nature and 1 other
  1. Nature

    Nightside condensation of iron in an ultrahot giant exoplanet

  2. BBC

    Wasp-76b: The exotic inferno planet where it 'rains iron'