: When a star with a mass less than two solar masses begins to shrink , its energy is released. But it reaches such a stage or state that it throws out its outer covering. As a result, a lot of energy is suddenly released which increases the brightness of the star. At this stage the star becomes so bright that it can be seen with the naked eye . It is now a Neva star and a new star. The remnants of this explosion are called white dwarf stars.