Example: Bright Line Spectrum

In this example, we show you the emission line (bright line) spectrum of an HII region in the nearby galaxy M101 obtained using the Palomar 5m Hale telescope by Liese van Zee*, Martha Haynes and John Salzer+.

Here is the original spectrum exactly as observed at the telescope. We don't record the colors in the image, only intensity (on a black and white scale) and wavelength.

Here, we have added color to the plot to emphasize visually that different wavelengths correspond to different colors.

Here, we plot intensity versus wavelength and label the elements responsible for the different lines: hydrogen (H), nitrogen (N), neon (Ne) and oxygen (0). We measure the intensities of the different emission lines, and use them to calculate the temperature and density of the gas in the HII region.

* Liese van Zee received her Ph.D. at Cornell University in August 1996. She was a Jansky postdoctoral fellowship at the National Radio Astronomy Observatory in Socorro, NM and then a postdoc at the Dominion Astrophysical Observatory in Victoria, British Columbia. She is now Associate Professor of Astronomy at Indiana University. There (apparently) is life after graduate school!

+ Once upon a time, long ago, John Salzer was a postdoc at the Arecibo Observatory where he co-captained the golf team and was winner of the Crazy Car rally one year. Today he is chairman of the Astronomy Department at Indiana University. His major failing in life is that he roots for U. Michigan but we are glad he has finally taken to wearing read. **Go Hoosiers!**.

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