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.
REM sleep follows NREM sleep and occurs 4-5 times during a normal 8-hour sleep period. The first REM period of the night may be less than 10 minutes in duration, while the last may exceed 60 minutes. The NREM-REM cycles vary in length from 70-100 minutes initially to 90-120 minutes later in the night.