When the Sun converts mass to energy, do the orbits of the planets change?
Good morning Skycat! The mass of the Sun is being reduced due to nuclear fusion processes in the Sun’s core, which convert part of the mass into energy. However, the effect on the orbits of the planets is very small and would not be measurable over any reasonable time period. If we imagine a planet orbiting the Sun at some speed, as the Sun loses mass its gravitational pull on the planet will weaken, so it will have trouble keeping it in the same orbit. The planet’s velocity will therefore take it further away from the Sun, and the orbital separation between the Sun and planet will increase. In 100 years, the Sun’s mass will decrease by 6.6 parts in a trillion. Therefore, the orbital separation of the planet will increase by 6.6 parts in a trillion and the orbital period will increase by 13.2 parts in a trillion. If the planet in question is the Earth (whose orbital separation from the Sun is around 150,000,000 kilometers and whose orbital period is 1 year), the Earth-Sun separation wi
