If our stone age ancestors had left us with stellar maps carved into rocks or painted on cave walls, we would have noticed striking differences with today's maps. Several tens of thousands of years ago, the constellations didn't look quite the same. Since despite what people thought up until the eighteenth century, the sky is everchanging. Stars move. They travel. And while this movement is often tiny, or even totally negligible over the scale of a human lifetime, it exists. This is a stroke of luck for astronomers, who found it to be the way to write some of the most beautiful pages of nineteenth and twentieth century astronomy, pages that go by the names of stars like 70 Ophiuchus, 61 Cygnus, Barnard, Epsilon Eridanus or Lalande 21185.

These were the true beginnings of the experimental hunt for exoplanets. The going was tough, with an extraordinary degree of groping in the dark, surprises and failures. In fact, none of the claimed planets of the time were confirmed. Why were there so many setbacks? Probably because the detection methods of the time were stretching limits. A tiny instrumental error was enough to see planets where really there was nothing. Dozens of years went by in a vain scrutiny of the stars in the hope of seeing a possible wobble that would betray the existence of a planet.