This ‘Roasting Marshmallow’ Exoplanet Is So Hot, It’s Raining Rubies And Sapphires There – News18

Last Updated:February 05, 2025, 09:53 IST

Scientists discovered WASP-121b, an exoplanet where metals rain from the sky. Located 858 light-years away, this ‘ultra-hot Jupiter’ challenges existing planet formation theories

Astronomers have made a significant discovery on strange planets that are extremely hot and swollen. While researching an exoplanet named WASP-121b, scientists found that it rains metals there. This planet becomes extremely hot during the day, with temperatures reaching 2,500°C (4,500°F).

In a new study, scientists found that this ‘ultra-hot Jupiter’ planet must have originated very close to its star. Research conducted with the help of the Gemini South Telescope challenges the current understanding of planet formation.

Beyond Our Solar System

Scientists first discovered planets (exoplanets) outside our solar system in the 1990s. Since then, more than 5,000 exoplanets have been discovered, many of these exoplanets are completely different from any planet in our solar system.

‘Hot Jupiters’ are one such type of planet. These gas giants are many times the size and mass of Jupiter and orbit so close to their star that their orbital period is only a few hours.

About one-third of the exoplanets discovered so far are ‘hot Jupiters’, which experience extreme temperatures, leading to their nickname, ‘roasting marshmallows’. Until now, it was believed that these planets first formed far away from their star and then slowly migrated inward. However, the recent study on WASP-121b raises questions about this theory.

New Discovery Is Surprising

Scientists used the Immersion GRating INfrared Spectrograph (IGRINS) mounted on the Gemini South Telescope. This marked the first time that the rock-to-ice ratio of a transiting planet was measured with a single instrument. Usually, such calculations require different instruments, which makes them prone to errors.

Features Of WASP-121b

The planet WASP-121b is located about 858 light-years away from Earth. Its mass is 1.2 times that of Jupiter, but it is so puffed-up that its diameter is 1.9 times larger than Jupiter. It is extremely close to its star, completing one orbit in just 1.3 Earth days. It is tidally locked, meaning one side always faces its star, while the other always faces space.

The daytime temperature on this planet reaches 2,500°C (4,500°F), causing the metals on its surface to evaporate and flow in its atmospheric currents. Strong winds of 17,700 km/h (11,000 mph) carry these metal-rich vapours to the night side, where they cool and fall as a rain of metal, ruby, and sapphire.

How Was This Planet Formed?

According to traditional models of planet formation, gas giant planets like WASP-121b form in cold regions far from their stars. However, this study found that WASP-121b had a very high proportion of rocky material. Chemical analysis of WASP-121b suggests that it formed in a place so hot that ice could not freeze there. This discovery is forcing scientists to reconsider the existing theory of planet formation.