Like most of the other things in this tour, Nebulae is also divided into groups. There are three, including Diffuse Nebulae, Planetary Nebulae, and Supernova Remnants. The word "Nebulae" was chosen to represent any 'fuzzy' object in the sky that wasn't sharp like a star, or a planet.
Diffuse Nebulae are mostly made of gas and dust and look like colorful clouds. Large ones are usually near a star formation or near a cluster of stars. When the radiation of a young, hot star reaches a nebula, it can make the gas of the nebula, which is made mostly of hydrogen, shine. This is called Emission Nebula. Other times the light from the hot star is refracted by the dust, turning it white or blue. This is called Refraction Nebula.
Planetary Nebulae happens when a hot star uses up its central nuclear fuel and lets go of a part of its mass. The star it leaves behind will eventually become a white dwarf, while the bubble-like outer shell floats off into space. They are very unstable, and their life-span is only about 10,000 to 50,000 years-relatively young compared to most things in the universe.
Right before a star dies, it explodes and becomes a supernova. Supernova Remnants are leftovers from that explosion. Supernova Remnants are important to us because they helped bring all elements heavier than boron to earth because these elements are only found on stars and supernova remnants. Supernova remnants are categorized into many different categories, but we armature astronomers wont get into that right now!
You are now at the end of your tour. What did you learn? Do you remember that quiz you took? Locate your answers and lets see if any of your answers have changed since the start of the tour!