Changes

#[[Nebula]]- A huge cloud of [[gas]] and dust stretching across space which collapses due to [[gravity]] to form [[star]]s.#[[Protostar]]- A glowing ball of [[gas]] and dust that is not yet hot enough for [[Nuclear Fusion|fusion]] to occur in its core.#[[Main Sequence Star]]- The longest and most stable period of a [[star]]s life when the outward pressure caused by [[Nuclear Fusion|fusion]] of [[Hydrogen]] in its core is balanced by the inward [[pressure]] caused by [[gravity]].#[[Red Giant]]- A [[star]] that has run out of [[Hydrogen]] for [[Nuclear Fusion|fusion]] so the [[pressure]]s are no longer balanced and its core collapses under [[gravity]] until the core is hot enough to [[Nuclear Fusion|fuse]] [[Helium]] into more [[massive]] [[element]]s. During this time the outer layers expand as the [[star]] cools but becomes brighter.#[[White Dwarf]]- A [[star]] which as run out of low [[mass]] [[element]]s to [[Nuclear Fusion|fuse]]. There is no more outward [[pressure]] due to [[Nuclear Fusion|fusion]] so the core collapses due to [[gravity]] into a ball of [[Iron]] and continues to glow for millions of years as it [[radiation|radiates]] its [[Thermal Energy Store|thermal energy]].#[[Black Dwarf]]- Once a [[White Dwarf]] has cooled enough it will no longer glow and become a [[Black Dwarf]]. These [[star]]s do not yet exist because the [[Universe]] has not existed long enough for [[White Drawf|White Dwarves]] to cool.