Searching for pale blue dots

IN 1990 Voyager took a photograph of Earth that was striking precisely because it showed so little. The spacecraft was six billion kilometres away at the time and the image it sent back was memorably described by Carl Sagan as a 'pale blue dot'. Imagine, then, how pale such a dot would be if the planet in the picture were 113,000 billion kilometres away. Yet this is the distance to the nearest confirmed exoplanet'a planet orbiting a star other than the sun. That gives some idea of the task faced by those who study these bodies. Only in the most special of circumstances can they actually see their quarry. Mostly, they have to work with indirect measurements, like watching for slight dips in the intensity of a star's light when a planet passes in front of it, a phenomenon known as a transit.But if indirect observation is all that is on offer, then astronomers must make the best of it. And, as numerous presentations to a meeting of the American Astronomical Society held in Seattle this week show, they have both done so, and have plans to do better in future.The most successful planet-hunting mission so far has been...Continue reading
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