We've now spotted some 300 extra solar planets, with rate of discovery increasing at an extraordinary rate. Astronomers have only seen one of these planets directly, the rest have all been inferred because the effect they have on their parent stars--changing their brightness or making them wobble. Of course, you have to be able to see the stars to do this kind of work so astronomers can only see extra solar planets in our local region of the Milky Way.

Until now. Gabriele Ingrosso at the National Institute of Nuclear Physics in Italy and pals say there is a way to spot planets in other galaxies. The trick is to exploit a phenomenon called microlensing in which the gravity of one star focuses the light from a more distant one towards Earth.