Why aren't stars green?

[Spacethingy]

Oh Be A Fine Girl/Guy Kiss Me...

No, I'm not nuts, it's star spectral types! O, B, A, F, G, K, and M.

Now, cool stars are red. Hotter ones like the Sun are yellow. Really hot ones are blue.

But... errrr... why are there no green ones? Green comes between yellow and blue in the spectrum after all... :tiphat:

 

[Urwumpe]

But... errrr... why are there no green ones? Green comes between yellow and blue in the spectrum after all... :tiphat:

Because you can't produce a green color by the black body radiation.

 

[Izack]

That graph is poorly labeled, to say the least. What is it a graph of?

 

[Urwumpe]

That graph is poorly labeled, to say the least. What is it a graph of?

A [ame=http://en.wikipedia.org/wiki/Planckian_locus]Planckian locus[/ame] in the [ame=http://en.wikipedia.org/wiki/CIE_1931_color_space]CIE 1931 color space[/ame]

 

[Ghostrider]

Can't have "green" nuclear fusion, sorry. You'll have to wait for wind-powered stars.

 

[Linguofreak]

Oh Be A Fine Girl/Guy Kiss Me...

No, I'm not nuts, it's star spectral types! O, B, A, F, G, K, and M.

Now, cool stars are red. Hotter ones like the Sun are yellow. Really hot ones are blue.

But... errrr... why are there no green ones? Green comes between yellow and blue in the spectrum after all... :tiphat:

Because the spectral colors consist of light at a single wavelength, whereas the light stars emit is at a mix of wavelengths.

The most intense wavelength in the Sun's spectrum actually is in the green/cyan region of the spectrum, but since there are other wavelengths mixed in as well we see it as white (or yellow, once the atmosphere has scattered some of the blue).

 

[jedidia]

This here might be a bit clearer than the graph Urwumpe posted above (you have to have Java runtimes installed, but who doesn't these days?):

http://www.lon-capa.org/~mmp/applist/blackbody/black.htm

You can screw around with the temperature and see the color spectrum for a blackbody with that temperature (in other words, a star with that temp). As you will see, green just isn't a dominant color at any temperature, there's always more red, yellow or blue. Indeed, as Linguofreak already said, our sun is about the greenest you can get (at about 5700K).

 

[SiberianTiger]

I can remember reading in an old SF book about a star that emitted an intensive green light because it had a high ratio of Zirconium in its atmosphere. This may be a complete anti-scientific in this case, but there are variety of spectrum classes of stars, and some "branch off" the main sequence. How different colour of these can be from the black body radiation spectrum?

 

[jedidia]

a slight green shift in the spectrum is of course possible for certain compositions, but that wouldn't be anything you could discern with your eyball mkI. The star would be "greener" in spectral analysis, but it certainly wouldn't look greener to the causual observer.

 

[Unstung]

Small bump, but I've found this related article before and found it interesting:
http://blogs.discovermagazine.com/badastronomy/2008/07/29/why-are-there-no-green-stars/
It explains why stars, such as our own sun, don't appear green.

 

[hribek]

If the sun became green, most of the current plantlife would have a very hard time.

 

[Poscik]

Also you have to take Doppler effect into account. Because of universe is expanding, stars are going further and further, so their light wavelenght increases. So light we see is a little bit different than original one emitted by star. But this is only applicable when looking on stars from Earth. So it is possible to see green stars, but universe would have to shrink veeeery fast.

 

[Linguofreak]

So it is possible to see green stars, but universe would have to shrink veeeery fast.

No, it's not, for the same reasons of mixed colors that make it impossible for stars to be green without Doppler shifting.