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How rare is our blue planet?

Duration: 03:34

Dr Lynn Rothschild explains how the Earth is located in the habitable zone of the Sun, an orbit that permits liquid water to exist. Astronomers hope to find planets similar to the Earth in the habitable zones of other stars as part of their search for places where life could exist.

Available since: Thu 12 Aug 2010

This clip is from

Horizon 2007-2008, Are we Alone in the Universe?

Science series. A planet has been discovered that could support life.

First broadcast: 04 Mar 2008

Image for Are we Alone in the Universe? Not currently available on BBC iPlayer

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