Jan. 11, 1999

NAU professor finds smog on extra-solar planets

Katie Paradis Public Affairs

A Northern Arizona University astronomer and her colleagues have discovered evidence of smog in the atmosphere of Gliese 229B, a large planet outside our solar system.

Published in the Dec. 11 issue of Science, NAU researcher Caitlin Griffith, an assistant professor of physics and astronomy and her colleagues, Roger V. Yelle, a visiting professor for Boston University and Mark Marley, an astronomy professor from New Mexico State University, analyzed spectra taken by astronomer Ben Oppenheimer with the Keck I telescope.

These observations indicate the giant planet, Gliese 229B, has reddish dust similar in color to the smog on Earth and Titan, a moon of Saturn. This and further considerations suggests that Gliese 229B has a smog. Unlike the smog on earth, which is produced by human activity, the smog on Gliese, like on Titan, is produced when its sun’s ultraviolet radiation breaks down the atmospheric methane. Gliese 229B has been an area of extensive study in the past three years. Discovered in 1995 by Noguyuki Nagajima, a Japanese astronomer, Gliese 229B is the only planet outside our solar system bright enough to be seen over its sun’s glare. Griffith and her colleague’s discovery is significant because it indicates that physical processes that shape the atmospheres of our solar system’s planets also occur in extra-solar planets.

The discovery of smog on a planet outside our solar system comes on the heels of discovery by Griffith and other colleagues of evidence of clouds on Titan, a moon of Saturn. These findings were published in the Oct. 8 issue of Nature.