The gravitational slingshot allows objects to change their speed and trajectory. If an object passes near a planet, it will change direction but due to its initial velocity, it does not pull into a planetary orbit. Instead, the object (i.e. asteroid, comet) gains a small fraction of the planet's orbital energy as it travels past. The gravitational slingshot can be considered as a hyperbolic orbit for it travels around a planet but in a non-circular orbit.

The planet will lose a "corresponding" amount of energy but this is almost impossible to see due the planet's large mass.