Looking to the stars on a clear night you can reveal colors at the brightest stars. Why stars have different colors?
The color of a star tells us something about it surface temperature, for instance our sun has yellowish color and it's surface temperature is 5500 °C. See below table for the spectral class summary of stars.

Courtesy Australia Telescope Outreach and Education

In 1666 Isaac Newton discovered that you can split light into a spectrum. Since that the resolving power of the observations became better and in 1815 Joseph von Fraunhofer discovered 574 black lines in the solar spectrum. owadays these black lines (absorption lines) are called "Fraunhofer lines" to his legacy.
In astronomy line spectra appear in two forms, absorption spectra, showing dark lines on a bright background (stars) and emission spectra with bright lines on a dark or black background (nebulae).

Absorption spectrum

Emission spectrum

In amateur astronomy it's also possible to reveal these spectra from stars and nebulae. Depending on the money you can/want to spend there are cheap solutions like the "Staranalyser 100" and very expensive spectrscopical systems. In my cas I use the Staranalyser 100 for my observations combined with a B/W camera (modded webcam or monochrome CCD camera) and a fast (F/5) telescope.

Click on the corresponding object to go to the related page
Aldebaran Arcturus Capella
Epsilon Lyra Polaris Sun
Vega Zeta Hercules
© Copyright Rob Kantelberg
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