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UPDATE: On July 23rd, NASA announced that the Kepler Mission located the closest 'twin' to earth so far. More from CBC.ca/news

Are we alone in the universe? We may be very close to finding out.

The Holy Grail of space science is the discovery of a planet just like ours: the right size, the right orbit around its sun, not too hot, not too cold – in the area dubbed the Goldilocks Zone. For millennia humans studying the stars had no idea if there were any other planets outside our solar system, let alone ones similar enough to ours to sustain life. The first extra-solar planet – or exoplanet – was only discovered in 1995.  Now, a new space-based telescope has discovered thousands more, and some of them may be just like Earth.

What are the odds of discovering another earth-like planet?

If the Kepler Space Telescope's discoveries are verified, and if what is true for this one tiny randomly-chosen area of the cosmos is true throughout, then our universe is probably chock full of habitable planets. This discovery would have enormous implications for the possibility of extra-terrestrial life. We would move from slim chance to great likelihood in one giant step. And we're about to take that step.

Planet Hunters follows the astrophysicists – many of them Canadian – at the forefront of the search for Earth's twin, and tells the little-known story of the two Canadians who invented the technique that made modern planet-hunting possible. Gordon Walker and Bruce Campbell also detected the first exoplanet ever discovered. But that's not what the history books say.

Based on the book Strange New Worlds: The Search for Alien Planets by Ray Jayawardhana.

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