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Astronaut Describes Search for Planets

The Kepler satellite will look for earth-sized planets.

<bt>Elementary students at Arlington Science Focus School got a lesson in outer space exploration Wednesday from Dr. Janice Voss, a former astronaut, who is now studying the cosmos in a new way.

During an assembly, Voss rolled a film of her fifth mission, aboard the shuttle Endeavor in 2000, and took questions about the space program.

"We have a lot of future scientists here," said principal Mary Begley. "We're very grateful to Dr. Voss for taking the time out to speak here."

At a presentation Tuesday night, she also spoke to students and their parents about the nature of her current scientific work on the Kepler project, a satellite-based program that will search beyond our solar system for Earth-sized planets. Using a sophisticated array of light sensors, Kepler will scan the Cygus region of space over the course of four years, measuring the light fluctuations of dwarf stars — stars similar to the sun — for the telltale signs of planets passing in front of them, a technique known as “transit photometry.”

"We're finding a whole bunch of new planets very quickly because of advances in technology," Voss told the audience. "Ours is the first technique for finding Earth-sized planets."

Finding the next Earth will likely prove a daunting task, she said. When a planet the size of Jupiter passes in front of a star, it decreases the star's light output by 1 percent. For a planet like Earth, the light is diminished by only .01 percent. Timing, Voss said, is the key.

"You're looking for a six-hour dip in the light from a star that might only happen once a year," Voss said. "If you look away, you might miss it. What we're going to do is pick a part of the sky and just stare at it for four years."

Finding an Earth-sized planet with an atmosphere capable of supporting life, Voss said, is even harder because scientists have to take into account the planet's proximity to the star that it is orbiting and its exact size.

"If it's too small, then it won't have enough gravity for an atmosphere to exist," she said. "If it's too big, it will have too much gravity, and what you'll get is a gas giant like Jupiter."

Voss also shared some of her favorite moments from her astronaut career. A science fiction fan, one of the most important to her, she said, was the night she curled up by a space shuttle window to read Isaac Asimov's "Foundation" by light of the Earth.

"It was the ultimate sci-fi moment," she said.

Voss said researchers on the Kepler project hope to find about 50 Earth-sized planets during the four-year mission. About 12 percent of solar systems in the Milky Way galaxy, she added, are believed to contain at least two planets. According to the project's Web site, http://kepler.nasa.gov, the Kepler satellite is expected to launch in 2007. The mission may be extended by two years. A subsequent mission will search for planets capable of supporting life.