What is a nebula ( astronomical term )?
A nebula (NEHB yuh luh) is a cloud of dust particles and gases in space. The term nebula comes from the Latin word for cloud. Early astronomers also used the term for distant galaxies outside the earth’s galaxy, the Milky Way. Such galaxies, called extragalactic nebulae, looked like hazy patches of light among the stars. But modern telescopes showed that extragalactic nebulae are actually systems of stars similar to the Milky Way. Today, most astronomers use the term nebulae only for the clouds of dust and gases in the Milky Way and other galaxies. They classify these masses into two general types: diffuse nebulae and planetary nebulae. Both types are also called gaseous nebulae. Diffuse nebulae are the larger of the two types. Some diffuse nebulae contain enough dust and gases to form as many as 100,000 stars the size of the sun. A diffuse nebula may occur near an extremely hot, bright star. The intense ultraviolet light from the star energizes the gas atoms of the nebula and enables
