Look for places where aliens are looking for us

Image: Earth transit
When Earth passes in front of the sun, it blocks a small part of the sun’s light. Potential observers outside our solar system might be able to detect the resulting dimming of the sun and study Earth’s atmosphere. (Credit: Axel Quetz / MPIA / NASA)

The past decade has brought about a revolution in astronomers’ ability to detect potentially habitable planets, and there’s much, much more to come. The problem will be identifying the likeliest places for life to lurk, and two newly published studies address that problem from two dramatically different perspectives.

One study takes an inward-looking perspective: If we were the aliens, how would we know about Earth?

The best planet-detection method that’s currently available to earthly astronomers looks for the telltale dimming of light as a planet crosses the disk of its parent star. But that dimming, known as a planetary transit, can be seen only when the planet and the alien star are lined up with Earth.

That suggests that Earth is most likely to be detected by observers on alien planets in a narrow strip of the sky where our planet can be seen crossing the sun.

Get the full story on GeekWire.

By Alan Boyle

Mastermind of Cosmic Log, contributor to GeekWire and Universe Today, author of "The Case for Pluto: How a Little Planet Made a Big Difference," past president of the Council for the Advancement of Science Writing.

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