Just 10 years after the first extrasolar planet was discovered, two teams of astronomers report the detection and measurement of infrared radiation from “hot Jupiters” circling nearby stars. The researchers predict these first observations will open a new window for understanding the evolution and characteristics of planets around other stars.
“We’re ecstatic,” says David Charbonneau of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and leader of one of the research teams. “We’ve been hunting for this light for almost 10 years.”
Charbonneau’s group used the Spitzer Space Telescope’s Infrared Array Camera to home in on the light from TrES-1, a “hot Jupiter” zipping around a Sun-like star about 500 light-years from Earth in the constellation Lyra. The astronomers tracked the intensity of two infrared “colors” as the planet passed behind its star, an event called secondary eclipse. The team subtracted the star’s radiation from the total seen when the planet was not eclipsed by the star.
Measuring the gas giant’s infrared radiation allowed the team to calculate its temperature — a sizzling 1,450° F (1,060 kelvins). Charbonneau suspects his group has also found the spectral fingerprint of carbon monoxide in the planet’s atmosphere, but, he says, “We’re going to go back and get more data.”
A separate group led by Drake Deming at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, used Spitzer’s Multiband Imaging Photometer to monitor the radiation at a single infrared wavelength — 24 microns — as a glowing gas giant world called HD 209458b passed behind and re-emerged from its star, which lies 153 light-years from Earth in the constellation Pegasus.
