What causes the 'starburst' galaxies to have the distinct red hue?

  • Thread starter Thread starter Joe D
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Joe D

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I have a general understanding of why they enter the starburst phase (cannibalization, etc.) and what they are (active star forming regions), but what I'm curious about is why they all seem to share the red glow characteristic. M51 is a great example of this. I'm pretty sure it's not a false colour or a multi-wavelength overlay.

It's just something I don't quite understand. Hopefully someone can shine some light on this for me.
 
To say that starburst galaxies are "red" is an oversimplification. Generally a "red" galaxy is a galaxy containing little gas and hence little star formation, that is usually elliptical. It contains only old stars, those stars are low mass (the massive stars having died off), and are consequently reddish.

You may be referring to the pinkish color often given to the H-alpha line in photos. This line is strongly emitted in the interstellar ionized hydrogen regions surrounding massive stars. Since the stars are massive, they only live a few tens of millions of years and are therefore characteristic of starburst regions.
 
To say that starburst galaxies are "red" is an oversimplification. Generally a "red" galaxy is a galaxy containing little gas and hence little star formation, that is usually elliptical. It contains only old stars, those stars are low mass (the massive stars having died off), and are consequently reddish.

You may be referring to the pinkish color often given to the H-alpha line in photos. This line is strongly emitted in the interstellar ionized hydrogen regions surrounding massive stars. Since the stars are massive, they only live a few tens of millions of years and are therefore characteristic of starburst regions.
 
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