Stars of the average size

   Upon reaching the average of the star (from 0.4 to 3.4 solar masses), the red giant phase, its outer layers continue to expand, the core collapse, and begin fusion reactions of carbon from the helium. Synthesis frees up a lot of energy, giving the star a temporary respite. For a star similar in size to the sun, this process may take about a billion years.

   Changes in the amount of energy emitted from the star forced to go through periods of instability, which include changes in size, surface temperature and the release of energy. Release of energy is shifted towards low frequency radiation. All this is accompanied by a growing mass loss due to strong winds and intense solar pulsations. Stars in this phase, known as late-type stars, OH-IR stars or Mira-like stars, depending on their exact characteristics. Emitted gas relatively rich in heavy elements produced in the depths of the stars, such as oxygen and carbon. Gas forms the expanding shell and chilled as the removal of a star, making it possible formation of dust particles and molecules. With a strong infrared radiation of the central star in these shells are ideal conditions for the activation of maser amplifier.

   Helium combustion reactions are very sensitive to temperature. Sometimes this leads to great instability. There are very strong pulsations, which would ultimately inform the external layers of a kinetic energy to be released and become a planetary nebula. In the center of the nebula remains the core of the star, which ostyvaya becomes a helium white dwarf, typically with a mass of up to 0,5-0,6 solar diameter and the order of the diameter of Earth.