In the summer of 1999, David Charbonneau, a Canadian studying at Harvard University, bought a cheap used car and drove from Cambridge, Mass., to Boulder, Colo., where he planned to do research for a doctorate in astronomy. The 25-year-old Charbonneau didn’t know it, but he was headed toward a rendezvous with history.
Charbonneau had arranged to work with Tim Brown, an astronomer in Boulder and a pioneer in the hunt for exoplanets — planets orbiting stars beyond our solar system. Brown and others concluded they had discovered early evidence of exoplanets by measuring tiny wobbles in the light emitted by stars; the wobbles, they reasoned, were caused by planets flexing their gravitational muscles. The findings met with mixed reviews in astronomy circles. One faction hailed it as a thrilling new chapter in humanity’s understanding of the universe. Another urged caution: the wobbles might be caused by phenomena unrelated to far-off planets.
The race was on to confirm what the wobbles suggested. Brown had helped to build a small but sophisticated telescope for a new method of planet hunting. The instrument could register the eclipse-like dimming of the light from stars if large planets crossed in front of them — or in astronomy-speak, transited. Over 10 nights late that summer, Charbonneau and his collaborators trained the telescope on a sun-like star 150 light years away that seemed like a good transit candidate.
Later, analyzing data from a night when they expected a transit to occur, Charbonneau and his colleagues noted a conspicuous dimming of the star lasting several hours. Data from a second night revealed the same thing. The upshot: they had detected the first exoplanet using the transit method, and in doing so laid to rest any lingering doubts about the existence of planets beyond our solar system and the validity of earlier observations based on the wobble approach. Furthermore, the transit data yielded, for the first time, a glimpse of an exoplanet’s vitals, including its radius, mass, density, surface gravity and temperature — all this from a planet born billions of years ago, travelling in light waves that had taken a century and a half to reach Charbonneau’s telescope. His team determined that exoplanet HD209458b is big, like Jupiter, and really, really hot.
To read more, click here.