Some are blue. Some are red. Some look like planets. From the Latin word for cloud, nebulae are some of the most spectacular objects in the universe.

Q: What is a nebula?
A: A nebula is a huge cloud made of dust and gas. There are many kinds of nebulae--some are home to forming stars, while others are made of gases thrown into space by dying stars.

Q: How big are nebulae?
A: It depends. Some are only one light-year across, while others are several hundred light-years in size. From Earth, we can only see a few of them.

Q: How many kinds of nebulae are there?
A: Wow! There are a lot! I could go on and on about nebulae...but I won’t. Here’s a short explanation of each kind of nebula:

Supernova remnants: A supernova is what a giant star is called at the end of its life. When the star explodes, it gives off as much energy as an entire galaxy. Much of the star is blown across space, and is called a supernova remnant. They are usually only a few light-years across.

Emission nebula: An emission nebula glows, and is made of hot gas. Emission nebulae are usually home to forming stars, and have a red glow. They form when ultraviolet light from a hot star reaches a cloud of hydrogen gas.

Reflection nebula: A reflection nebula glows because it reflects the light of nearby stars. Reflection nebulae are usually blue, and are often home to forming stars.

Dark nebula: A dark nebula is a cloud of dust that blocks the light of anything behind it. Dark nebulae are usually several hundred light-years across.

Planetary nebula: A planetary nebula has nothing to with a planet, but kind of looks like one when seen through a small telescope. Actually, planetary nebulae are made of gas thrown off by stars at the end of their lives.