2  Hot Jupiter transits are easy to measure

Astronomers in the 1950s realised that the transits of planets like Jupiter could be detected if a star was being continuously observed when the transit occurred. Of course, Jupiter transits only once every 12 years, and there is a less than one in 1000 chance of the orbit being lined up enough for transits of Jupiter-like planets to be seen at all (more on this later). With 1950s technology, observing thousands of stars continuously for years was utterly impossible, so no one tried. With twenty-first-century technology – digital cameras, cheap large-scale data storage and powerful computer processing capabilities – transits of hot Jupiters are easy to measure.