Hot Jupiters are the most extreme type of planets we've seen beyond our solar system. One year on one of these gas giants is less than 10 days because they are so close to their stars. Some weird and wonderful effects can be seen on these planets.

An artist's illustration of the planet KELT-20b which orbits a blue-white star.
This is an artist’s illustration of the planet KELT-20b which orbits a blue-white star. The giant planet is so close to its star (5 million miles) that the torrent of ultraviolet radiation from the star heats the planet’s atmosphere to over 3,000 degrees Fahrenheit. NASA, ESA, Leah Hustak (STScI)

A paper in the journal Astrophysical Journal Letters describes a hot Jupiter with a distinctive atmosphere. The planet KELT-20b is located 400 light-years away and is bombarded by UV radiation. This creates a layer in the atmosphere similar to Earth's, which absorbs UV rays, by heating the planet's atmosphere to over 3000 degrees Fahrenheit.

The upper layers of the atmosphere are hotter than the lower layers of the atmosphere. On our planet, this layer is formed by ozone, but on KELT-20b, the layer is formed from metals that have boiled.

We never knew how the host star affected the atmosphere of a planet.

The researchers used data from Hubble in the near-infrared wavelength as well as data from NASA's Spitzer Space Telescope to look at the signals of water and carbon monoxide coming from the planet. The emission spectrum for KELT-20b is different from other hot Jupiters.

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