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Q & A: Colors of galaxies?

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Most recent answer: 10/24/2010
Q:
First Question, I would like to know what makes the galaxies in this image have colour, and how their colour is created. Second Question, I would also like know if this image is considered ‘mathematically beautiful ‘are there any equations that could be applied to this image that would make it beautiful? Third question as scientists why would you say/ or what would you say contributes to this picture that makes it beautiful? Thank you very much for your time
- Aurora (age 20)
UK
A:
We're not sure which image you're referring to. Some image are made using some sort of artificially enhanced colors. Others use the plain colors of the objects themselves. Let's say that your describing one of the latter.

First of all the color of a star or collection of stars such as a galaxy depends on the average temperature.  For example our middle aged sun has a nice yellow color.  Young stars are more hot due to their youthful vigor and have a bluish temperature  whereas very old stars are relatively cool and have a reddish color. Eventually they turn dark, at least to our eye.   The relationship between temperature and color is a well known phenomenon discovered by the German physicist Max Planck in the late 19th century. 

Another phenomenon that can affect the color of a galaxy is the so-called redshift.  It is well established by observations that the the universe seems to be expanding.  The net result is that galaxies far away from us have large receding velocities. This causes a Doppler shift in the frequency and wavelength of the light.  So galaxies very far away look more red than those closer nearer.   See  http://en.wikipedia.org/wiki/Redshift for more details.

Astronomers can enhance the various colors in their photographs by using color filters in their telescopes.  Some of the photographs you see are conglomerates of several photographs taken with different filters.  No equations are involved.
I answer your third question by repeating the old saying "Beauty is in the eye of the beholder". 

LeeH
 

(published on 10/24/2010)

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