Right now, the asteroid's name is (101955) 1999 RQ 36 and scientists are looking for a name that is a bit easier to say. It was first discovered on September 11th, 1999 and is about a third of a mile in diameter. It is one of the most hazardous to Earth because of its size and proximity and scientists think that it may collide with Earth between 2169 and 2199.
The spacecraft will launch in 2016 and will spend a couple of years chasing the asteroid before it will be able to catch it. Once the spacecraft is within reach, it will get as close as it can and using a robotic arm, it will "kiss" the surface and collect a sample, that will be brought back to earth to help scientists estimate the likelihood of a collision.
To enter the contest, students must be younger than 18 and all entries must be submitted by a parent or teacher by Dec. 2. (Contest rules are at planetary.org/name.)