This asteroid was discovered around a month ago, is this normal, do we often find out about a month in advance that an asteroid is quite close to us? so, most asteroids are relatively small, and they tend to be very dark. they are actually quite difficult for us to detect. the big ones, we know where they are. the smaller ones, it is only when they get closer to us that we can spot them. sometimes, it can be a month or so before they make their closest approach, before we even know they exist. but once we have spotted them, we can track them really accurately and we can be confident working out that this one is not going to hit us. good news for us, we will be able to sleep tight tonight. you talk about the size, and also, researchers like yourselves, how exciting is something like this for you? is it something you can gain intelligence on? as you said, this is a once in a decade or so type event. this asteroid is probably about 70 metres or so in diameter. it is going to pass by quite ....