Estimate is that there might be about ~10 of these object passing through every year, so it's not a lot to start with. In addition asteroids are relatively smal

Estimate is that there might be about ~10 of these object passing through every year, so it's not a lot to start with. In addition asteroids are relatively small and hard to spot since they are inert. We managed to spot this one because we were lucky it came so close to earth.