Researchers say they've identified a protective stratosphere-like layer around an exoplanet called WASP-33b. The layer acts a sort of sunscreen, protecting the blazing hot planet from ultraviolet light.

Researchers detailed their new discovery -- made with the help of data collected by NASA's Hubble Space Telescope -- in the Astrophysical Journal.

Finding an atmospheric layer outside our solar system isn't unheard of, but scientists weren't expecting to find such a layer on such a piping hot exoplanet.

"Some of these planets are so hot in their upper atmospheres, they're essentially boiling off into space," study co-author Avi Mandell, a planetary scientist at NASA's Goddard Space Flight Center, explained in a press release. "At these temperatures, we don't necessarily expect to find an atmosphere that has molecules that can lead to these multilayered structures."

Researchers recognized the alien stratosphere by spotting a temperature inversion around WASP-33b. The Earth's stratosphere is also characterized by a temperature inversion.

On Earth, the stratosphere sits above the troposphere, the lowest atmospheric layer where clouds and weather exist. In the troposphere, heat is concentrated at the bottom and temperatures cool as altitude increases. The opposite is true in the stratosphere, where ozone traps the sun's ultraviolet radiation.

The Hubble telescope was able to observe the exoplanet's atmosphere by detailing the way light passed through it as the alien world dipped behind its host store. In addition to documenting the exoplanet's atmospheric temperature inversion, the Hubble's Wide Field Camera 3 also identified the molecule responsible fore the inversion -- titanium oxide.

"These two lines of evidence together make a very convincing case that we have detected a stratosphere on an exoplanet," said lead study author Korey Haynes, a graduate student at George Mason University.

Studying atmospheric layers can reveal clues about how alien planets evolved.

"Understanding the links between stratospheres and chemical compositions is critical to studying atmospheric processes in exoplanets," said co-author Nikku Madhusudhan, a researcher at the University of Cambridge. "Our finding marks a key breakthrough in this direction."