Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Do less bright stars have redder spectrum?

  1. Dec 31, 2013 #1
    Do less bright stars have redder spectrum?
  2. jcsd
  3. Dec 31, 2013 #2


    User Avatar
    Science Advisor
    Gold Member

    Not necessarily. Stars radiate pretty much like black bodies, so the spectrum depends on temperature like so:
    The hotter the star, the more it radiates, and the more is the spectrum shifted towards higher frequencies. Colder stars would then normally radiate less and be redder.
    But that doesn't take into account the radiative area of the star(so, size). Red giants, for example, are relatively cold, and radiate small amounts of energy per unit surface area, but since the area is so large, they can be extremely bright.

    However, stars on the main sequence(http://en.wikipedia.org/wiki/Main_sequence) have their temperatures and sizes dependent on mass only(and age and metallicity, but to a lesser degree). So as long as you restrict yourself to these only, your statement is true.
  4. Dec 31, 2013 #3
    Thank you very much for such an excellent answer with a diagram and the link to the wikipedia article on Main sequence stars. That was very helpful.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook