Nebulae are the Cradle of the Stars
Have you ever wondered how stars are made? Nebulae are the nurseries of the universe. Their appearance look like fluffy cotton balls in the sky; they act much like the clouds we have at home on earth. They are gigantic clouds of helium and hydrogen gases that can span trillions of miles of light years across. These are formed from interstellar mediums, or dust found between galaxies. These materials contract when it gets hotter, eventually getting so hot that it’s ignites hydrogen fuel. When this happens, the light emitted is ultraviolet radiation, which lights up the orbiting gases and matter around the nebulae. Sometimes, nebulae form images that appear on earth and are thusly named after their images. The Horsehead Nebula and the Crab Nebula are examples of these silly names. There are a few different kinds of Nebulae:
Emission Nebulae are very hot with lots of energy. They have a distinct color of pink or red because they have has a lot of hydrogen gas. An example of the Emission Nebulae is the Orion Nebulae, which is red and is found under the Orion constellation.
Reflection Nebulae have lower energy and appear blue in reflection to their scattering white light. When their light is emitted, they light up particles nearby to the nebulae. Emission and Reflections are often very close to each other in proximity. The closest example of a Reflection Nebulae is the Witch Head also found in the constellation of Orion.
Lastly, there are Planetary Nebulae, which are made when a star runs out of fuel to burn. When a star dies, it expands to form a Giant Red Star, that swallows up everything in its path. This is the Visua l Nebulae. Then it shrinks and dissipates after thousands of years. A fun fact is that scientists back in the 1700s believed that these balls of gas were actually gigantic planets in the sky.
Read more at: http://www.seasky.org/celestial-objects/nebulae.html
