Stars and their color - temp and/or movement

ex-minister
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Stars and their color - temp and/or movement

 Well, I need to expose my lack of scientific training again. Damn theology.

 

I have enjoyed astronomy for years and in college I learned that the color of the stars was related to how hot they are. Redder stars are cooler and blue stars are hotter.

So you have a roygbiv (red orange yellow...) spectrum.

 

Lately I have been reading things on the big bang and authors are relating star color to the doppler effect. Stars moving towards us are blue and away are red. The vast majority are apparently red because the universe is expanding. Then I was reading most stars are white. What they heck does that mean?

 

Can someone clear up this up for me? How can the color of stars represent both the temp and movement when it is only one color? What color would a hot star (blue) moving away from us (red) be? And how could astronomers determine if the color was related to one or the other of these properties?

 

 

 

 

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I'm sure you know more about

I'm sure you know more about astronomy than I do, but I too am trying to spend more time catching up on it. I just happened to be collecting some photos and simulated artwork of colors and space. The only thing I think you didn't consider is the composition of the star. The following is a simple explanation of the colors of stars and composition, and if you want to dig deeper look into light filters, spectrum analysis, and relativity of wavelength emissions.

 

 

Why Are Stars Different Colors

The Brightest of Stars

If you are an amateur astronomer you may have observed that stars are not as uniform as they first appear. If you were to observe the stars you would notice that they are different colors. So why are star’s different colors? The difference in colors actually depends on a lot of different factors. The first is the composition of a star. While stars are all basically composed of atoms some stars have other trace elements in them that can alter the wavelengths of light that they emit. The next factor is surface temperature. This is the most significant contributor to a star’s color. The change in temperature changes the wavelength of light a star emits. The last factor is distance in relation to the Doppler Effect.

 
     

Composition does play a role in the color of light a star emits. This is because not all stars are formed exactly the same way. The reason is due to being formed in different nebulas. Nebulas in the interstellar medium are largely composed of hydrogen the main fuel for star creation. However they do carry other elements. The mix of these other elements varies from nebula to nebula. The change in color these elements add to stars is not very obvious. However it is important in the field of spectroanalysis. Depending on the kind light an element burns scientist can analyze a star’s light and basically determine its elemental composition.

The most important factor to a star’s color has to be its surface temperature. If you have ever seen an open flame you would understand why. A blue flame is flame burning at very high temperatures. A yellow flame has temperatures that are cooler than blue flames and red flames are the coolest of all. The same thing happens with stars. Very hot stars tend to be blue stars. Stars with an average surface temperature become yellow stars like our sun. The coolest stars are Red Dwarfs.

Last there is Doppler Effect also known as red or blue shift. If you are familiar with the Doppler Effect you known that distances can extend or contract waves. It’s the

fire

truck analogy where a siren sounds closer as the fire truck approaches and sounds lower as it leaves. With light it becomes bluer if the distance between a star and an observer is shrinking and redder if it is growing. This evidence was used to determine that the universe is expanding as galaxies and stars showed a red shift

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ex-minister wrote:

Well, I need to expose my lack of scientific training again. Damn theology.

I have enjoyed astronomy for years and in college I learned that the color of the stars was related to how hot they are. Redder stars are cooler and blue stars are hotter.

So you have a roygbiv (red orange yellow...) spectrum.

Lately I have been reading things on the big bang and authors are relating star color to the doppler effect. Stars moving towards us are blue and away are red. The vast majority are apparently red because the universe is expanding. Then I was reading most stars are white. What they heck does that mean?

Can someone clear up this up for me? How can the color of stars represent both the temp and movement when it is only one color? What color would a hot star (blue) moving away from us (red) be? And how could astronomers determine if the color was related to one or the other of these properties?

The red shift has nothing to do with the stars intrinsic color. It has to do with the spectral lines of the elements in the star shifting to the red when moving away. Onlly when very far away and thus moving away very rapidly does it affect the apparent visual color of the star. I don't have numbers for that but I assume it is a well known rule of thumb in the textbooks.

 

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 I wanted to ask this

 I wanted to ask this question for a long time and finally there's such a topic. Why does Sirius seem so strange? It looks like shimmering all the time, even when other stars and planets give steady light. It also seems to have more colors, like red and blue together. Maybe the atmosphere's doing it, but I don't understand why other stars and planets just don't look the same. I can't believe the star has huge multi-colored plasma fireworks on its surface as it looks like.

 EDIT: OK, apparently it's some optical effect due to a difference size between a planet and a star, but I still don't get it. I've seen Sirius twinkle even if other stars held still. Maybe it doesn't work for "small" stars and "big" planets.

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 There is a trillion x a

 There is a trillion x a trillion ^10x10000 tons of dirt, dust and other shit between us and the actual light. Also there is an atmosphere which changes things when we view stars.

 

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The brighter the body, and

The brighter the body, and the greater the distance, the more susceptible it is to atmospheric and space-borne disturbances. They all twinkle, but the brightest twinkles the most. Sirius is, as I recall, the fourth brightest body in the sky. But the brightest body that is outside the solar system. It should therefore twinkle more than any other.

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A_Nony_Mouse wrote:
...

The red shift has nothing to do with the stars intrinsic color. It has to do with the spectral lines of the elements in the star shifting to the red when moving away. Onlly when very far away and thus moving away very rapidly does it affect the apparent visual color of the star. I don't have numbers for that but I assume it is a well known rule of thumb in the textbooks.

AND

Ultraviolet shifts down to visible light as red shifts to infrared. Thus the full "spectrum" is maintained until the star is so far away that it runs out of UV to fill the blue end of the emission.

 

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