- #1
tarekatpf
- 140
- 1
Do less bright stars have redder spectrum?
In summary, the spectrum of a star depends on its temperature and size, with hotter stars having a higher frequency and colder stars being redder. However, the size of a star also plays a role, as seen with red giants which can be extremely bright despite being relatively cold. When considering only stars on the main sequence, their spectrum depends on their mass, age, and metallicity.
- #2
Bandersnatch
Science Advisor
- 3,485
- 3,000
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.
1. Why do some stars appear redder than others?
The color of a star is determined by its surface temperature. Cooler stars have a redder spectrum, while hotter stars have a bluer spectrum.
2. How does the brightness of a star affect its spectrum?
Brighter stars tend to have a bluer spectrum, while dimmer stars have a redder spectrum. This is because brighter stars have higher surface temperatures.
3. Are all red stars dimmer than blue stars?
No, not all red stars are dimmer than blue stars. The brightness of a star is dependent on its size, temperature, and distance from Earth. There are some red giants, for example, that are actually brighter than some blue main sequence stars.
4. Can a star change color over time?
Yes, a star's color can change over time. As a star evolves, its surface temperature changes, which can cause its color to shift from red to blue or vice versa.
5. Can we determine a star's age based on its color?
Yes, the color of a star can provide clues about its age. Generally, younger stars are bluer in color, while older stars tend to be redder. However, other factors such as a star's mass and chemical composition can also affect its color, making it difficult to accurately determine its age based on color alone.
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