What is a Nebula?
“Nebula” is the Latin word for cloud. It was originally used to describe anything in the night sky that had a cloudy or diffuse appearance, and that wasn’t a comet. Early in the 20th Century, however, it was discovered that some of these nebulae were actually “island universes” (galaxies or globular clusters). Since then, the word refers to specific types of objects: Planetary nebulae are usually spherical and are the expanding shells of material ejected from dying stars. They get … Continue reading →