Asymptotic giant branch forming helium (known as hydrogen burning), and a very large envelope of material of composition similar to main-sequence stars. When a star exhausts the supply of hydrogen by nuclear fusion processes in its core, the core contracts and its temperature increases, causing the outer layers of the star to expand and cool. The star becomes a red giant, following a track towards the upper-right hand corner of the HR diagram. Eventually, once the temperature in the core has reached approximately , helium burning (fusion of helium nuclei) begins. The onset of helium burning in the core halts the star's cooling
Red giant stars develop into supergiants that follow an evolutionary track that takes them back and forth horizontally over the HR diagram, at the right end constituting red supergiants. These usually end their life as a type II supernova. The most massive stars can become Wolf–Rayet stars without becoming giants or supergiants at all. Red giants with known planets: the M-type HD 208527, HD 220074 and, as of February 2014, a few tens of known K-giants including Pollux, Gamma Cephei and Iota Draconis. Although traditionally it has been suggested the evolution of a star into a red giant will render its planetary