Stars start life as a nebula. As it fades and dies, the star dissolves into another nebula. Early astronomers used the term as a catch all referring to any astronomical entity stretching beyond the Milky Way. However, as we gain more information about our universe, nebulae have emerged to be in a specific class all their own.

Planetary nebulae are created when a star’s core becomes unstable. Unable to sustain itself, the inner temperature of the core increases causing the outer layer to be separated from the star. The overheated core remains and imparts a radiant glow onto the ejected dust. The Hubble Space Telescope has captured many images that reveal the complexity of these astronomical objects. The planetary type of nebulae generally form the shape of a ring or bubble.

The Crab Nebula is a well-known interstellar cloud that falls into a combination of categories. A supernova remnant is formed when a star explodes and is accompanied by a shock wave. The shock wave picks up other dust it intersects with when ejected. In addition to falling under this category, the Crab Nebula is a pulsar wind nebula. Meaning it is powered by the heavily magnetized winds of a neutron star.

When a nebula cannot generate its own light and must reflect light from surrounding stars, it’s called a reflection nebula. Reflection Nebulae are often blue in color and are often seen near Emission Nebulae. The Orion Nebula is an example of this. Emission nebulae burn very hot and are found where new stars are being born. Absorption or Dark Nebulae appear black in color since they block light around them. Any ray of light shinning in the pathway of a Dark Nebula will be absorbed and not pass through.