NASA’s Spitzer Space Telescope, for the first time, has detected light from distant planets that lie external to our own Solar System. So far, about 130 extra-solar planets or exo-planets, including two recent ones found by Spitzer, have been found indirectly by methods called ‘wobble’ and ‘transit’.
While ‘wobble’ technique shows the presence of a planet by the gravitational force it exerts on its parent star, thus making the star wobble, the ‘transit’ method does so when the planet passes in front of its star, making the star dim or ‘blink’. Both methods, using visible-light telescopes, indicate the size and mass of the planets.
NASA’s Goddard Space Flight Center’s (GSFC) Dr Drake Deming, who is studying one of the two planets recently detected by Spitzer, said, “Spitzer has provided us with a powerful new tool for learning about the temperatures, atmospheres and orbits of planets hundreds of light-years from Earth.” Harvard-Smithsonian Center for Astrophysics’ Dr David Charbonneau, lead author of the study of the second planet found, said, “It’s fantastic. We’ve been hunting for this light for almost 10 years, ever since extra-solar planets were first discovered.”
Spitzer directly detected the warm infrared glows of the two recently found ‘hot Jupiter’ planets, named HD 209458b and TrES-1. Hot Jupiters are extra-solar gas giants moving around their parent stars. They absorb starlight and glow brightly in infrared wavelengths.
To tell the shine of these planets apart from the hot stars, astronomers first used Spitzer to gather the total infrared light from both the planets and the stars. When the planets went behind their stars, the astronomers measured the infrared light coming from the stars only. This read exactly how much infrared light belonged to the planets. Upcoming Spitzer observations that work over a range of infrared wavelengths would give additional data about the planets’ winds and atmospheric compositions.
Sara Seager, an astronomer belonging to Deming’s team, said that HD 209458b was found to have a temperature of between 850 °C and 1450 °C, and probably has water vapor in its atmosphere. Upcoming Spitzer observations that work over a range of infrared wavelengths would give additional data about the planets’ winds and atmospheric compositions.
“It’s an awesome experience to realize we are seeing the glow of distant worlds,” said Charbonneau, adding that TrES-1’s temperature is about 800 °C.
HD 209458b and TrES-1 are two of the six known hot Jupiters. While the Deming study has been published in
Nature magazine’s Web site, the Charbonneau study would be featured in an upcoming issue of the
Astrophysical Journal.
