How do astronomers know which asteroids or comets pass by us? Q: Do we really know where comets and asteroids go once they leave our space?
Astronomers know which comets and asteroids pass by us by observing the path or orbit these objects take around the sun. Just like the planets and moons, asteroids and comets have orbits which can be mathematically calculated based on observations. These elliptical (egg-shaped) orbits are relatively unique. When a new asteroid or comet is discovered, astronomers have to observe it enough times to be able to determine the orbit. There are certain numbers they use to define the orbit and we call those numbers ‘orbital elements.’ We can use the orbital elements to predict the future positions of comets and asteroids within the solar system.
