Loading astro130..

Escape velocity is the velocity needed for an object to escape a planet’s (or a different object’s) gravitational pull.  It is defined as:

{\text{v}_{esc}}={\sqrt{\frac{2GM}{R}}}

where vesc is the escape velocity [km/s], G is the gravitational constant = 6.67259 x 10-__11__ N m2 /kg2, M is the mass of the planet [kg], and R is the radius of the planet [m].

Examples of Escape Velocities
Object Velocity
Moon 2 km/s
Earth 11.2 km/s
Sun 620 km/s
White Dwarf 6,500   km/s (assuming M~2x1030 kg, R=6.4x106 m)
Neutron Star 23,000   km/s (assuming M~4x1030 kg, R=10,000 m)
Black Hole greater than the speed of light!

In the physical sciences, we usually define a black hole in terms of its escape velocity:

A black hole is an object whose escape velocity is greater than the speed of light.

Please use a modern browser to view our website correctly. Update my browser now