[ROBERT]

On a "star trail" photograph I took of Orion I noticed a few green trails, see:-
http://oriontrails.mysite.wanadoo-members.co.uk
Are these green trails all due to close double stars with one yellow and one blue,
 or is there such a thing as a single green star (sun)?

[DoctorBeaver]

I've never heard of a green star

[Solvay_1927]

Good question.

I've never heard of green stars either - but why can't you get a green star?  The colour of a star depends primarily on how hot it is (as far as I understand it), because the temperature determines the primary/predominant frequency (or wavelength) of the light emitted.  As the temperature rises (from red through to blue), doesn't it pass a point at which it peaks in the green light region?

So what's the reason we never see green radiation?  (The same applies to a blackbody, or a potter's kiln, say - you don't see the glow turning from red to yellow to green - it goes straight from yellow to white, and beyond that to bluey-white.)  Can anyone out there help us with an explanation?


"Do infants enjoy infancy as much as adults enjoy adultery?"

[A Big Mug]

I think it has something to do with the human eye being sensitive to certain frequencies.  Stars pumping out more energy in the green wavelenth tend to get shoved into a yellow by our eyes. Purple is another color that confuses the eye in those situations.  I think it gets picked up as blue or something.

[ukmicky]

http://curious.astro.cornell.edu/question.php?number=14

Michael                                      

[neilep]

Excellent link Michael..thanks.

So, I presume we can only see green and purple stars through telescopes that are able to detect them, but the human eye will never see them.....that's a shame .

Men are the same as women.... just inside out !!

[DoctorBeaver]

Great link, Micky

[ROBERT]

Thanks for the response everyone.
Like Solvay 1927 & Doctor Beaver, I had heard of "red hot" and "white hot" but never "green hot". I had heard that many stars are in close pairs, (binary systems), so if one of the pair was blue and the other yellow then the pair would appear green,
 (blue + yellow = green).
According to ukmickey's link there are single green stars, perhaps this explains why extra terrestrials are depicted as "little green men": they have a green sun tan, (joke).  

 

[Solvay_1927]

Michael - nice one.

Robert - I wonder if alien cultures have their own celebrities who glow lurid lime green, due to the amount of fake sun-tan they put on?
(Hmmm, does this reply belong under the "Orange People" thread ... ?)


"Do infants enjoy infancy as much as adults enjoy adultery?"

[ROBERT]

According to ukmickey's link our sun's visible light output peaks in the
"yellow-green" part of the spectrum.

So why are plants (photosynthesis) not optimised to "yellow-green" light ?,
(excuse me for stating the obvious but most plants reflect green light).  

http://www.botany.uwc.ac.za/ecotree/photosynthesis/spectrum.htm

Plants seem to be optimised for purple light, (see above link).
Has our Sun, or Earth's atmosphere, ever been purple ?,
(perhaps billions of years ago when photosynthesis first occurred).