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“Nebula” comes from the Latin word for cloud.
“Nebulae” is the plural. It is loosely applied to anything that looks fuzzy or extended
in a telescope.
To astronomers in the early 1900s, galaxies were classified as nebulae, because they looked like fuzzy
“blobs”. Today we know galaxies are collections of billions of stars. We will limit our nebulae to clouds of
gas floating in space.
The Sun is just a star, an average star. It just looks
so big and bright, because it is so close, compared
with other stars.
Emission Nebulae are made of ionized hydrogen. When free protons recapture
electrons, the electrons emit specific wavelengths (colors) of light, often ending up
with a distinctive pink color.
An emission nebula is caused when a cloud of hydrogen gas is heated by a nearby O or B star
(25000 K).
Reflection Nebulae are caused when clouds of dust scatter the
starlight from behind them. They tend to be bluer in color, as short
wavelengths of light scatter easier than longer wavelengths.
http://www.youtube.com/watch?v=8x41n9thAU8&feature=topics
Quiz!Identify what the following pictures are: Emission NebulaReflection NebulaDark NebulaPlanetary NebulaGalaxy
Number 1 – 8 on a separate sheet