Exoplanet that rains Iron “WASP-76b”

On Earth, we might experience giant hailstones. But, imagine a pile of molten iron falling from the atmosphere as rain! After all, it’s not possible on Earth due to our sustainable climatic conditions.

But we have a similar kind of planet in our solar system itself. That is, Uranus and Neptune which rains diamonds in its atmosphere. First of all, what makes the planets special to rain iron or diamonds in its atmosphere?

Is it their orbital motion? Or is it their internal nature?

I would say it’s because of both the properties. Uranus and Neptune are commonly known for their ice called “ice giants” of our solar system. Astronomically, ice refers to all lighter elements that contain hydrogen. So, water, ammonia and methane that’s present in the planet makes them icy. The beautiful bluish colour of these planets is the result of methane traces in their atmosphere.

In both the planets, the hydrogen-helium atmosphere (which is 3,000 kms) lies in an ice layer that is almost 17,500 kilometres thick. Simulations suggest that gravity present in these planets compresses the ice in this middle layer to higher densities which leads their internal heat to raise their internal temperature to several thousand kelvins. Having such an intense temperature and pressure more than one million times greater than the atmospheric pressure on Earth, it tends to compress ice into a hot, dense fluid.

In this exoplanet “WASP-76b” (Wide Angle Search for Planets is an international consortium of several academic organisations performing an ultra-wide-angle search for exoplanets using transit photometry.) which is discovered in the year 2016, is about 390 light-years away from Earth and is located in Pisces constellation. This exoplanet rotates its parent star WASP-76 which is a main sequence star and comes under the category of Hot Jupiter which exceeds 2400 degree Celsius, hot enough to vaporise metals. Moreover, these exoplanets orbit their host star very closely and it is tidally locked (Only one of its sides is facing the star at all times). From the obtained data from Very Large Telescope (VLT) in Chile, the researchers observed that metallic rainfall was seen only during the transition of day to night and was not encountered during the transition of night to day. The team then went on to analyse the chemical variations between day and night on the planet.

This mystery has been encountered by the first author of the article (David Ehreneich) that it rains iron on the dark side of the exoplanet. Therefore, during the day, temperature shoots up-to 2400 degree Celsius which makes the molecule separate into atoms and the iron evaporates into the atmosphere to form metallic clouds. These clouds with vaporised iron are then driven by strong winds at the speed of about 16000 Kmph to cause rain.

Till now, more than 4341 exoplanets have been discovered outside our solar system. This means that we will have lots and lots of interesting information in future days.