NASA have put out a press release about Hubble Space Telescope observations of WASP-33b.
WASP-33b is the hottest of the WASP planets, being the only one so far found orbiting a very hot A-type star. A team led by Korey Haynes from NASA’s Goddard Space Flight Center, have used Hubble to show that WASP-33b has a “stratosphere”. The spectrum in the infra-red is best explained by a temperature inversion caused by the presence of Titanium Oxide in the atmosphere.
Titanium Oxide is noted for its ability to absorb light, which is why it is often used in sunscreen lotion. NASA’s graphic shows how an absorbing layer in the atmosphere produces a “temperature inversion” with a hotter layer higher up:
By comparing models with and without a temperature inversion to the spectrum of WASP-33b, as observed with Hubble’s WFC3 instrument, Haynes et al “make a very convincing case that we have detected a stratosphere on an exoplanet”.