Nebulas are conglomerates of gaseous and dust particles that spread throughout space. The gas is mostly made of hydrogen and helium. Dust in space is made of tiny particles of solid matter. Astronomers think stars are born in nebulas.
There are many types of nebulas. The main types are planetary nebulas; diffuse nebulas; supernova remnants; reflection nebulas and dark nebulas. Planetary nebulas are “skin” (or shells) that an old, average-sized star sheds during the red giant stage. Diffuse nebulas are objects in space with no definite shape. Supernova remnants (or remains of supernovas) often give off radiation, which is like the radiation from TV or radio stations. A reflection nebula is made when a cloud of highly reflecting (maybe snow white) space particles is brightened by a nearby star whose temperature may not be hot enough to make the gas glow. Finally, there are dark nebulas. These are clouds are sometimes silhouetted by gas or the light of stars behind them.