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
Omega Carinae Omega Carinae is a shell star, having a circumstellar disk of gas surrounding its equator. The luminosity class of III indicates it has evolved into a giant star, having exhausted the hydrogen at its core and left the main sequence. The effective temperature of 13,275 K in its outer envelope is what gives this star the blue-white hue that is characteristic of B-type stars. This star is rotating rapidly with a projected rotational velocity of , which gives a lower limit to the star's azimuthal velocity along the equator. The critical equatorial velocity, at which the star would begin to