Hot Jupiters and Luminous Tempests: New Discoveries Made in the Atmospheres of Distant Planets

Astronomers have recently made two discoveries concerning the atmospheres of two distant planets, including evidence of a stratosphere high above the surface of an exoplanet, and the formation of a massive storm in Neptune’s atmosphere.

The discovery of an exoplanet’s stratosphere was made using infrared images made by the Hubble Space Telescope of what is known as a "hot Jupiter", WASP-121b, orbiting a sun-like star 880 light-years away. Hot Jupiters are gas giants that have orbits that are very close to their stars, with WASP-121b’s year only lasting a little more than 30 hours. This planet’s stratosphere is showing evidence of the presence of water molecules, and the atmosphere’s temperature increases as one gets farther from the planet’s surface, much like what is seen in Earth’s stratosphere.

"This result is exciting because it shows that a common trait of most of the atmospheres in our solar system — a warm stratosphere — also can be found in exoplanet atmospheres," explains study co-author Mark Marley, with NASA’s Ames Research Center. "We can now compare processes in exoplanet atmospheres with the same processes that happen under different sets of conditions in our own solar system."

Astronomers have also found something odd going on in an atmosphere closer to home, in particular a massive new storm that has formed on Neptune. This storm is 9,000 kilometers across, or three-quarters the diameter of the Earth. The storm was spotted during a test run of twilight observations at the W. M. Keck Observatory in Hawai’i, with the storm dramatically increasing in brightness between June 26 and July 2.

"Seeing a storm this bright at such a low latitude is extremely surprising," explains graduate student Ned Molter, with University of California, Berkeley. Molter spotted the storm complex during the aforementioned test run. "Normally, this area is really quiet and we only see bright clouds in the mid-latitude bands, so to have such an enormous cloud sitting right at the equator is spectacular."

"Historically, very bright clouds have occasionally been seen on Neptune, but usually at latitudes closer to the poles, around 15 to 60 degrees north or south," adds Professor Imke de Pater, of UC Berkeley’s Astronomy Department. "Never before has a cloud been seen at, or so close to the equator, nor has one ever been this bright."