Starwatch: The solar system in action

Because of their enormous distance from us, the stars remain stationary with respect to each other (at least during the span of a human lifetime), creating the celestial sphere - an imaginary sphere of arbitrary size on which you can paint the locations of these fixed objects.

A coordinate system, right ascension and declination can be defined using the celestial sphere, counterparts of longitude and latitude on Earth. In theory, we can trace the motion of moving objects with respect to this system: planets, asteroids comets "