The Search for Life Beyond Earth

Is there life anywhere else in the universe? This is one of the most profound questions scientists have ever asked. So far we have found no definite answer — but we have very good reasons to keep searching, and the discoveries so far are exciting. Searching carefully and honestly, rather than simply guessing, is exactly how science works.

Most exoplanets are too far away and too dim to photograph directly. So how do we find them? One clever method is the 'transit' technique: when a planet passes in front of its star, it blocks a tiny fraction of the starlight, making the star dim ever so slightly. By watching for these regular little dips in brightness, astronomers can detect planets they cannot even see.

Life as we know it needs liquid water to exist. That is why scientists focus on the 'habitable zone' — the range of distances from a star where a planet is neither too hot nor too cold for liquid water on its surface. Earth sits perfectly in the Sun's habitable zone. Many exoplanets have been found in the habitable zones of their stars.