Nebulae

Fuzzy Patches in Space

Photo Credit: Cygnus Loop, Hubble Space Telescope

The term "nebula" was originally used by astronomers to refer to any "fuzzy' patch in the sky that could be easily distinguished by a telescope, but was not sharp like stars or planets. Charles Messier, an eighteenth century French astronomer, published his famous catalogue of these objects in 1784 so that he and other comet hunters would not confuse them with comets. We now know that some of the "nebulae" of Messier's catalogue are other galaxies and some are clusters of stars. On the plasma graph, "nebula" refers to clouds of interstellar dust and gas within our own galaxy made visible by their interaction with nearby stars or star remnants.

Types of Nebulae:

Emission Nebulae

Interstellar plasma which absorbs and re-emits electromagnetic radiation from close by hot young stars...

Reflection Nebulae

Dust particles which scatter and reflect light from nearby bright young stars...

Planetary Nebulae

Ejected matter from a low mass star near the end of the star's life...

Supernova Remnants

Ejected matter from a high mass star near the end of the star's life...

Some Nebula References:

1. Abell, George O., David Morrision, and Sidney C. Wolff. Exploration of the Universe (6th Ed., 1993 Version). New York: Saunders College Publishing, 1993.
2. Chaission, Eric and Steve McMillan. Astronomy Today. New Jersey: Prentice Hall, 1993.
3. Harwit, Martin. Astrophysical Concepts (2nd Ed.). New York: Springer-Verlag, 1988.
4. Kaler, James B. Stars. New York: Scientific American Library, 1992.
5. Kaufmann, William J. III, Universe (3rd Ed.). San Francisco: Wh. H. Freeman, 1991.
6. Malin, David. A View of the Universe. Sky Publishing, 1993.
7. Malin, Stuart. The Greenwich Guide to Stars, Galaxies and Nebulae. Cambridge: Cambridge University Press, 1989.
8. Roth, Gunter Dietmar (Editor). Compendium of Practical Astronomy, Volume 3: Stars and Stellar Systems. New York: Springer-Verlag, 1994.
9. Zelik, Michael and Elske v. P. Smith. Introductory Astronomy and Astrophysics (2nd Ed.). New York: Saunders College Publishing, 1987.

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We recommend The Web Nebulae site for those interested in more Nebula images.