Your My Hy-Vee account provides access to your history, allows you to print records, submit multiple prescriptions at once and more. Learn more. This healthy lifestyle program emphasizes eating for good health, weight loss and being physically active. Beginâ¢ is not a âdietâ- Beginâ¢ is a plan to help with lifelong wellness.
Given sufficient temperature and pressure, 4 hydrogen nuclei fuse to produce helium, at the same time giving off energy in the form of heat and light and other forms of radiation. This means that stars, with a few exceptions such as super-massive stars, last for many billions of years.
During most a star's lifetime, the interior heat and radiation is provided by nuclear reactions in the star's core. This phase of the star's life is called the main sequence. Before a star reaches the main sequence, the star is contracting and its core is not yet hot or dense enough to begin nuclear reactions. So, until it reaches the main sequence, hydrostatic support is provided by the heat generated from the contraction.