- #1
tarekatpf
- 140
- 1
Do less bright stars have redder spectrum?
Do less bright stars have redder spectrum?
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SUMMARY
The brightness and color spectrum of stars are not directly correlated, as demonstrated by the behavior of black body radiation. While hotter stars emit higher frequency light and appear bluer, cooler stars can be redder but may still be bright due to their large radiative areas, such as red giants. Main sequence stars have their temperature and size primarily determined by mass, with age and metallicity playing a lesser role. Therefore, the assumption that less bright stars are redder is not universally applicable.
PREREQUISITES- Understanding of black body radiation principles
- Familiarity with stellar classification, particularly main sequence stars
- Knowledge of stellar temperature and mass relationships
- Basic concepts of radiative area and luminosity in astrophysics
- Research the properties of black body radiation in astrophysics
- Learn about the Hertzsprung-Russell diagram and its significance in stellar classification
- Explore the relationship between stellar mass, temperature, and luminosity
- Investigate the characteristics of red giants and their role in stellar evolution
Astronomy students, astrophysicists, and anyone interested in understanding the complexities of stellar brightness and color relationships.
- #2
Bandersnatch
Science Advisor
- 3,607
- 3,258
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.
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.
- #3
tarekatpf
- 140
- 1
Bandersnatch said: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.
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.
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