The closest discovered planet to us, outside of our solar system, is “Epsilon Eridani b“, a mere stone’s throw away at 10.4 light years. In our solar system we’ve found a mess of new planets (well, “dwarf planets” anyway) by taking pictures of the sky and literally looking for them. However, to find extra-solar planets (“exoplanets”) we’ve had to rely on methods that are decent at finding planets that are huge and close to their suns, and bad at finding planets that are small and far from their suns. That right there is the essential reason why we haven’t found any truly Earth-like planets yet: a planet like the Earth is too small and far from the Sun to be readily detectable. In our solar system, there are two clusters of asteroids that share Jupiter’s orbit.