When this is over, the cycle starts over; the original star dies and becomes a white dwarf. White Dwarf The core of a white dwarf star surrounds itself with layers of hydrogen, which still burn, continuing to fuse.
REM sleep is important because it is the restorative part of our sleep cycle. Typically, you begin the sleep cycle with a period of non-REM sleep followed by a very short period of REM sleep. The period of non-REM sleep is made up of stages 1 to 4. Each stage can last from 5 to 15 minutes.
Sleep requirements decline from infancy to early adulthood, level off, then decline again in old age. Stage 4 sleep increases in old age. Ten-year-olds are in REM sleep about 1.5-2 hours per night. Stage 4 sleep increases in old age.