Another crucial debate topic: Are there points of light in a fixed firmament, or are there balls of gas
undergoing nuclear fusion grouped into galaxies in an expanding universe.
The class D (for Degenerate) is the modern classification used for white dwarfs — low - mass stars that are no longer
undergoing nuclear fusion and have shrunk to planetary size, slowly cooling down.
«A planet is a sub-stellar mass body that has never
undergone nuclear fusion and that has sufficient self - gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters,» the proposal said.
«In the process of
undergoing these nuclear fusion reactions, the sun emits large amounts of heat and light.