First Light From Distant Planets Seen by Telescope

Brian Handwerk
for National Geographic News
March 23, 2005

NASA's Spitzer Space Telescope has detected the light from two distant planets. The scientific first opens a new era in which scientists can directly observe the extrasolar worlds that orbit distant stars.

It's also the first step toward actual photographs of planets outside our solar system.

Two separate teams made the discoveries, which were announced yesterday at a NASA press conference.

"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," said Drake Deming of NASA's Goddard Space Flight Center in Greenbelt, Maryland. The scientist is the lead author of a new study on one of the planets.

More Discoveries Likely

Just ten years ago extrasolar planets were nearly unknown. But indirect observation techniques have produced many recent discoveries.

Indirect techniques include detecting a planet from the "wobble" its gravity causes in the planet's host star. Another method is to observe the "darkening" of a star when an otherwise indetectable planet passes in front of it.

The new Spitzer observations are the first times extrasolar planets have been detected on their own merits, so to speak, rather than because of their effects on other celestial bodies.

"The past decade has been an exciting time for the study of planets," said David Charbonneau, an assistant professor of astronomy at the Harvard-Smithsonian Center for Astrophysics, in Cambridge, Massachusetts.

"We've detected over 130 [extrasolar planets] and been able to infer some of their properties indirectly," said Charbonneau, the lead author of the second study. "Now, for the first time, we can isolate the light from the planet itself—that's a precious piece of information."

Launched in August 2003, the infrared Spitzer Space Telescope trails behind Earth during its orbit around the sun.

Spitzer captured infrared emissions from the two extrasolar planets, known as HD 209458b and TrES-1. The two planets shine brightly because of their status as "hot Jupiters." The gas giants are similar to Jupiter but orbit so close to their respective stars that they become superheated to some 1,000° Kelvin (727° Celsius/1,340° Fahrenheit).

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