A109: A planetary nebula is a nebula that is made up of gas and plasma. They are made by certain types of stars when they die. They are named this because they look like planets through small optical telescopes.They do not last for very long compared to a star, only tens of thousands of years.
At the end of a normal-sized star's life, in the red giant phase, the outside layers of a star are disposed of. Because the outside is gone, the star shines brightly and is very hot. The ultraviolet radiation given off by the center of the star ionizes the gas and plasma that was thrown out from the star. This is what causes a planetary nebula to look like it does.
Planetary nebulae are very special objects because they can help make more stars. When a star dies, the metals that were in the core of the star are sent to other places in the universe. The only place that these metals form are in stars. This is called nucleosynthesis.
The pictures of these nebulae show that they have very weird shapes. Scientists are not sure why they are not all spheres. There are many theories about why they are not. They think that binary stars, stellar winds and magnetic fields might be part of the reason they look so special.