When he was a boy in Ontario, Canada, David Charbonneau didn’t know that he would grow up to discover new planets. Back then, he was fascinated with the stars. He liked to find the constellations in the night sky. In high school, he read a book for adults about the universe. “I didn’t understand most of it, but it excited my interest in space,” he says.

Now he hunts for planets that orbit stars beyond our Sun. They are called extrasolar planets. More than 600 of these planets have been found so far. Most of them are giants like Jupiter and Saturn. Dr. Charbonneau is searching for smaller, rocky planets with the conditions for life: planets like Earth.

STARS THAT WOBBLE

From Earth, no one can see an extrasolar planet, even while using the most powerful telescopes. Astronomers had to figure out how to find them.

In 1995, Dr. Geoffrey Marcy and Dr. Paul Butler developed the first technique, the wobble method. They knew that the Sun is a star. The pull of the Sun’s gravity keeps Earth and the other planets in their orbits. The gravity of each planet also pulls on the Sun, making the Sun wobble a little.

Dr. Marcy and Dr. Butler reasoned that any star that had planets would also wobble. After a long search, they found some stars that wobble and declared that they had found new planets. But some astronomers thought the two scientists were wrong... that they had not really found planets.

David Charbonneau helped show that Dr. Marcy and Dr. Butler were right. In 1999, he and Dr. Robert Noyes found a way to tell if wobbling stars really have planets. If a star had a planet, then the planet might cross in front of, or transit, the star. Then the planet would cast a shadow, blocking some of the star’s light. The star would become dimmer.

In a parking lot in Boulder, Colorado, David Charbonneau and Dr. Timothy Brown set up a small telescope. They watched wobbling stars. One night, they saw star HD 209458 become dimmer. The star had a planet! They had confirmed the wobble method of planet hunting. Since then, scientists have found 80 transiting planets.

TELESCOPES AROUND THE WORLD

David Charbonneau is now Dr. Charbonneau, an astronomer at Harvard University in Massachusetts. He uses many telescopes around the world. “I can sit here and run telescopes in Arizona or in California and not even have a joystick,” he says. “I am sleeping while the telescopes are run by a computer program.”

Dr. Charbonneau is also on the team that runs NASA’s Kepler Space Telescope. Kepler orbits Earth, watching for the dimming of stars. Kepler has found more than 2,300 shadows moving across stars. So far, other astronomers have confirmed that 61 of those shadows are indeed planets.

Among those 61 new planets, the Kepler team has found three Earth-like planets orbiting stars much like our Sun. The first is a large planet, known as a super Earth. The other two are about the size of Earth.

All life as we know it needs water in its liquid form. So for a planet to have life, it may have to be just the right distance from its star. If the planet is too close, it will be too hot for liquid water. If the planet is too far away, then it will be too cold. Like the porridge in “Goldilocks and the Three Bears,” the planet needs a temperature that’s “just right.” Astronomers call this perfect distance the “Goldilocks Zone.”

The newly found super Earth lies in the Goldilocks Zone, but the two Earth-sized planets are too close to their star.

BREATH OF LIFE?

Dr. Charbonneau is also taking the next step: he is analyzing the air on transiting planets. “We came up with a trick,” he explains. “As the planet passes in front of the star, some of the light passes through the atmosphere of the planet. Imprinted on that light will be the fingerprint of whatever atoms or molecules are present in the atmosphere.”

He hopes to find oxygen and other gases needed for life as we know it. He says, “If we find transiting rocky planets and analyze their atmospheres, the big prize may be life.”

How does the section “Breath of Life?” contribute to the development of ideas in the text?

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