NASA Hubble Space Telescope Discovers a Layer of 'Sunscreen' on a Distant Planet

NASA's Hubble Telescope may have detected a layer of "sunscreen" on a planet. It's spotted a stratosphere, one of the primary layer of Earth's atmosphere, on a massive and blazing-hot exoplanet known as WASP-33b.

The presence of a stratosphere can actually provide details about the composition of a planet and how it formed. The atmospheric layer includes molecules that absorb ultraviolet and visible light, acting as a kind of "sunscreen" for the planet that it surrounds. Until now, though, researchers were unsure whether these molecules would be found in the atmospheres of large, extremely hot planets in other solar systems.

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

In Earth's atmosphere, the stratosphere sites above the troposphere, which is the turbulent, active-weather region that reaches from the ground to the altitude where nearly all clouds top out. In the troposphere, the temperature is usually warmer at the bottom and cools down at high altitudes.

In the stratosphere, though, the temperature increases with altitude, a phenomenon known as temperature inversion. In this case, the researchers identified a temperature inversion in the atmosphere of WASP-33b, which has about four and a half times the mass of Jupiter.

"These two lines of evidence together make a very convincing case that we have detected a stratosphere on an exoplanet," said Korey Haynes, lead author of the new study, in a news release.

The researchers used data from previous studies to measure emission from water and compare it to emission from gas deeper in the atmosphere. The scientists determined that emission from water was produced in the stratosphere at about 6,000 degrees Fahrenheit. The rest of the emission came from gas lower in the atmosphere that was at a temperature about 3,000 degrees Fahrenheit.

"Understanding the links between stratosphere and chemical compositions is critical to studying atmospheric processes in exoplanets," said Nikku Madhudsudhan, one of the researchers. "Our finding marks a key breakthrough in this direction."

The findings are published in the Astrophysical Journal.

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