Thus the emission nebulae are a characteristic pinkish-red in colour. As the solar winds from the ionising star blow away the central regions, the nebula dissipates. Emission nebulae are usually isolated regions of much larger interstellar clouds . A quantity which defines the amount of 'work' a body or a system can perform. Some common forms of energy are kinetic energy which is embodied by a moving object, potential energy which is embodied by an object suspended in a gravitational field or radiant electromagnetic energy which is carried by photons .
All forms of energy are interchangeable, e.g. nuclear energy to heat to light.
Energy level . The energy associated with a quantum state . Consider a plane perpendicular to the axis of spin of a rotating body passing through its centre. The equator is the great circle where the plane cuts the surface. Equatorial mounting .