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Added link to Kepler's laws
The '''escape speed''' associated with any celestial body, such as a [[star]], a [[planet]], a [[dwarf planet]], or a [[moon]], is the speed at which an object, starting from the body surface, would have to travel to be able to escape the body's gravity. An object in motion has escaped the gravity of a celestial body if the body cannot cause the object to fall back toward it or to remain in a closed [[orbit]] around it.
The '''escape speed''' (also known as escape velocity) associated with any celestial body, such as a [[star]], a [[planet]], a [[dwarf planet]], or a [[moon]], is the speed at which an object, starting from the body surface, would have to travel to be able to escape the body's gravity. An object in motion has escaped the gravity of a celestial body if the body cannot cause the object to fall back toward it or to remain in a closed [[orbit]] around it.
== Concept ==
== Concept ==
When an object is traveling exactly at escape speed, it is in a parabolic orbit with the body at the focus of the parabola. A parabolic path is open; hence an object following such a path will never return to the body.
When an object is traveling exactly at escape speed, it is in a parabolic orbit with the body at the focus of the parabola. A parabolic path is open; hence an object following such a path will never return to the body.
An object traveling at a speed slower than the escape speed normally moves in an ellipse, which is a closed path. So long as that path does not intersect the body surface, the path is an orbit.
An object traveling at a speed slower than the escape speed normally moves in an ellipse, which is a closed path. So long as that path does not intersect the body surface, the path is an [[orbit]]. It will follow [[Kepler's laws of planetary motion]].
An object traveling ''faster'' than escape speed is following a ''hyperbolic'' orbit, which is also open. The object will always be traveling faster than a minimum speed even after infinite time.
An object traveling ''faster'' than escape speed is following a ''hyperbolic'' orbit, which is also open. The object will always be traveling faster than a minimum speed even after infinite time.