Artist's Illustration of Temperature Inversion in Exoplanet's Atmosphere
Using NASA's Hubble Space Telescope, scientists detected a stratosphere on the planet WASP-33b. A stratosphere occurs when molecules in the atmosphere absorb ultraviolet and visible light from the star. This absorption warms the stratosphere and acts as a kind of sunscreen layer for the planet below.
WASP-33b's stratosphere was detected by measuring the drop in light as the planet passed behind its star (top). Temperatures in the low stratosphere rise because of molecules absorbing radiation from the star (right). Without a stratosphere, temperatures would cool down at higher altitudes (left).