Cloudy with a risk of precious stones: It rains liquid jewels on WASP-121b

You might think our local gas giants are extreme - Jupiter with its orbit of the moon and Saturn with its iconic rings, but they are nothing compared to WASP-121b. This exoplanet caught the attention of astronomers a few years ago when they realized that its atmosphere was warm enough to bleed metal. It's on the day page. On the cooler night side, it rains gems because that's the weather you get in a truly extreme world like the WASP-121b. 

This is what's called a hot Jupiter because it's a gas giant ... and it's extremely hot. WASP-121b was the first exoplanet to have its atmosphere characterized by the Hubble Space Telescope. This solar system is about 900 light-years away, a distance that would make most exoplanets difficult or impossible to scan directly. However, WASP-121b is 20 percent larger than Jupiter, and it orbits so close to its star that it emits a lot of energy - it is 10 times hotter than any previously discovered exoplanet. 

Today, WASP-121b reaches temperatures of 4,600 degrees Fahrenheit (2,500 Celsius), causing heavy metals to boil in the upper layers of the atmosphere. Tides are locked, so the same side is always facing the star. New analysis of WASP-121b shows that the night side is only 2,200 degrees Fahrenheit, positively frosty compared to today's side. The team estimated wind speeds on the planet at more than 11,000 miles per hour (17,702 kilometers per hour). 

This is the first time we have been able to collect data from a superheated exoplanet like this, and astronomers have made some guesses about how the temperature gradient between the halves works. The model indicates that the night side of the WASP-121b has clouds with metal content including iron, titanium and corundum. The latter is the primary component of rubies and sapphires. The color depends on trace metals such as titanium (sapphire) and chrome (ruby). 

So what happens when the gemstone clouds blow over the terminator from night to day? The hostile, overheated environment is likely to cause the minerals to fall out like rain. But instead of water, this is a rain of gems. Yes, molten gemstones, but everything on WASP-121b is molten. It is a fascinating world, and as such, this planet will be one of the first to be observed by the James Webb Space Telescope. The newly launched spacecraft has a larger mirror and better infrared sensitivity, which is ideal for analyzing the composition of exoplanet atmospheres. NASA is still calibrating Webb, but the first observation should begin this summer.