Surface gravity is the gravitational acceleration experienced at the surface or skin of a celestial body. It is represented by the symbol \(g\), and its SI unit is [metres per second squared] \((m/s^{2})\).

$$g=\frac{GM}{R^{2}}$$

where \(M\) is the mass of the celestial body, \(R\) is its radius, and \(G\) is the gravitational constant.

The surface gravity of a celestial body determines the weight of objects on its surface. The greater the surface gravity, the heavier objects will feel. For example, the surface gravity of Earth is approximately 9.8 m/s², meaning that an object with a mass of 1 kilogram weighs 9.8 newtons.

The surface gravity of celestial bodies can vary significantly depending on their size and density. The surfaces of planets and moons generally have lower surface gravity than the surfaces of stars and neutron stars. This is because planets and moons are less massive and dense than stars and neutron stars.

The surface gravity of celestial bodies can also be influenced by the presence of other celestial bodies. For example, the surface gravity of the moon is reduced slightly by the presence of Earth's gravity. This is because the gravitational force of Earth pulls the moon away from its centre of mass, causing the moon to experience a centrifugal force that reduces its surface gravity.