# Why aren't there any green stars? **URL:** \ **Category:** Factual Questions\ **Created:** [December 27, 2006, 5:18pm UTC](https://boards.straightdope.com/t/why-arent-there-any-green-stars/385767 "2006-12-27T17:18:28Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![John\_DiFool](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_difool/32/19543_2.png) [@John\_DiFool](https://boards.straightdope.com/u/John_DiFool)\ **Post date:** [December 27, 2006, 5:18pm UTC](https://boards.straightdope.com/t/why-arent-there-any-green-stars/385767/1 "2006-12-27T17:18:28Z")
Or are there? The [Wikipedia](http://en.wikipedia.org/wiki/Stellar_classification) article doesn’t directly answer my question, but I am sure there’s a reason (just as there’s a reason why there’s no purple stars either). ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [December 27, 2006, 5:26pm UTC](https://boards.straightdope.com/t/why-arent-there-any-green-stars/385767/2 "2006-12-27T17:26:23Z")
In brief, it has to do with the blackbody spectrum. Hot objects emit a broad spectrum of light, not just a single color. At the point where the temperature is such that the blackbody radiation peaks in the green, the overall spectrum is such that the emitted light appears largely white. You can play with the blackbody spectrum vs. temperature in a Java applet [here](http://www.lon-capa.org/~mmp/applist/blackbody/black.htm) ---
**Author:** ![Sampiro](https://avatars.discourse-cdn.com/v4/letter/s/2acd7d/32.png) [@Sampiro](https://boards.straightdope.com/u/Sampiro)\ **Post date:** [December 27, 2006, 5:49pm UTC](https://boards.straightdope.com/t/why-arent-there-any-green-stars/385767/3 "2006-12-27T17:49:50Z")
There have been at least two green stars, Marta and Vina respectively, both located in Orion. [Cite](http://en.wikipedia.org/wiki/Orion_Slave_Girl). One blew up. ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [December 27, 2006, 6:50pm UTC](https://boards.straightdope.com/t/why-arent-there-any-green-stars/385767/4 "2006-12-27T18:50:01Z")
What QED said. The color we perceive from a radiating object is produced by the wavelength range in which it produces the most photons of radiation within the visible-light range. Anything emitting radiant light is doing so in a bell curve, with what we perceive as its color at the peak of the curve. Something which glows red is pumping out the majority of its photons within the red-light range. It’s radiating in the infrared, too, but we don’t see that; we feel it as heat. And in the yellow and white ranges as well, but to such a lesser amount that they are swamped by the red light. Increase its temperature, and it will glow yellow-white – it’s still pumping out red light, but the majority of its photons are in the yellow range, with enough further up the scale to produce that whitish tinge. Increase it still further, and it’s white-hot. Still producing red and yellow photons, but also now green and blue as well. The mixture of all spectral colors, with green at the peak emission range, gives us the effect of white light. Increase the temperature yet again, and the peak is into the blue range, giving you the blue-white light of the hottest naked-eye stars. It’s not impossible for something to produce green light, but it would have to be glowing at a single monochromatic range in the green, or have the other wavelengths of “white light” filtered out by an interposed filter. The junk you can buy to throw on fires to produce green flames burns at exactly the right temperature to produce the green flames. But when something emits black-body radiation, such as a star, it’s over a range defined by that bell curve. This, by the way, is why no purple stars either. (The hottest blue-white stars glow violet-white, at the high end of the visible-light spectrum.) But purple as a visible color is an admixture of red and blue – and would therefore require two peaks. You might in theory get this effect from a binary pair appearing to the eye as one star, one of which is red and the other blue-white. But (though not an expert in optics) I suspect that the effect of the combination would not be purple but white, the red peak, the blue peak, and the overlapping range between them where neither star’s emission is at its radiating peak but both are radiating to some extent, producing an additive whole equivalent to the white mid-range star. ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [December 27, 2006, 7:08pm UTC](https://boards.straightdope.com/t/why-arent-there-any-green-stars/385767/5 "2006-12-27T19:08:46Z")
There used to be more, but they kept getting color-corrected to light orange in post-production. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [December 27, 2006, 7:16pm UTC](https://boards.straightdope.com/t/why-arent-there-any-green-stars/385767/6 "2006-12-27T19:16:53Z")
[QUOTE=Polycarp] The junk you can buy to throw on fires to produce green flames burns at exactly the right temperature to produce the green flames. [/QUOTE] Excellent post, overall, but I must disagree with this statement. Although the energy to produce the light does, in fact, ultimately come from the heat of the flames, the specific color(s) are an intrinsic property of the material involved and is in no way determined by temperature. Green is commonly produced by copper compounds; other compounds can produce different colors all across the visible spectrum. This specificity of color associated with particular substances is the basis for spectroscopy, the technique astronomers use to determine the composition of stars and other radiant bodies. ---
**Author:** ![Bosda\_Di\_Chi\_of\_Tricor](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bosda_di_chi_of_tricor/32/16845_2.png) [@Bosda\_Di\_Chi\_of\_Tricor](https://boards.straightdope.com/u/Bosda_Di_Chi_of_Tricor)\ **Post date:** [December 27, 2006, 8:03pm UTC](https://boards.straightdope.com/t/why-arent-there-any-green-stars/385767/7 "2006-12-27T20:03:51Z")
There **has** been **fiction** about Green Stars. [http://www.amazon.com/gp/search?search-alias=stripbooks&field-keywords=&author=carter&select-author=field-author-begins&title=green+star&select-title=field-title&subject=&select-subject=field-subject&field-publisher=&field-isbn=&node=&field-binding=&field-age=&field-language=&field-dateop=before&field-datemod=0&field-dateyear=2009&chooser-sort=rank!%2Bsalesrank&mysubmitbutton1.x=35&mysubmitbutton1.y=10](http://www.amazon.com/gp/search?search-alias=stripbooks&field-keywords=&author=carter&select-author=field-author-begins&title=green+star&select-title=field-title&subject=&select-subject=field-subject&field-publisher=&field-isbn=&node=&field-binding=&field-age=&field-language=&field-dateop=before&field-datemod=0&field-dateyear=2009&chooser-sort=rank%21%2Bsalesrank&mysubmitbutton1.x=35&mysubmitbutton1.y=10) Lin Carter’s tribute to EWdgar Rice Burroughs’ Barsoom series. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [December 27, 2006, 10:51pm UTC](https://boards.straightdope.com/t/why-arent-there-any-green-stars/385767/8 "2006-12-27T22:51:11Z")
[QUOTE=Bosda Di’Chi of Tricor] There **has** been **fiction** about Green Stars. [http://www.amazon.com/gp/search?search-alias=stripbooks&field-keywords=&author=carter&select-author=field-author-begins&title=green+star&select-title=field-title&subject=&select-subject=field-subject&field-publisher=&field-isbn=&node=&field-binding=&field-age=&field-language=&field-dateop=before&field-datemod=0&field-dateyear=2009&chooser-sort=rank!%2Bsalesrank&mysubmitbutton1.x=35&mysubmitbutton1.y=10](http://www.amazon.com/gp/search?search-alias=stripbooks&field-keywords=&author=carter&select-author=field-author-begins&title=green+star&select-title=field-title&subject=&select-subject=field-subject&field-publisher=&field-isbn=&node=&field-binding=&field-age=&field-language=&field-dateop=before&field-datemod=0&field-dateyear=2009&chooser-sort=rank%21%2Bsalesrank&mysubmitbutton1.x=35&mysubmitbutton1.y=10) Lin Carter’s tribute to EWdgar Rice Burroughs’ Barsoom series. [/QUOTE] I recall an old one called _The Star of Life_, about a green star who’s light had mutagenic properties upon those who lived there. The people who moved there became immortal ( and some other stuff I think ), but their children where superhumanly intelligent sociopaths. Two of the stars “pushed back” in _Starplex_ were green as well. ---
**Author:** ![jayjay](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jayjay/32/6765_2.png) [@jayjay](https://boards.straightdope.com/u/jayjay)\ **Post date:** [December 28, 2006, 12:20am UTC](https://boards.straightdope.com/t/why-arent-there-any-green-stars/385767/9 "2006-12-28T00:20:16Z")
There’re lots of green stars. Mostly at conventions of Esperantists. ---
**Author:** ![danceswithcats](https://avatars.discourse-cdn.com/v4/letter/d/9e8a1a/32.png) [@danceswithcats](https://boards.straightdope.com/u/danceswithcats)\ **Post date:** [December 28, 2006, 12:51am UTC](https://boards.straightdope.com/t/why-arent-there-any-green-stars/385767/10 "2006-12-28T00:51:20Z")
Kermit, Gumby, and The Hulk come to mind. 😉 ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [December 30, 2006, 12:46pm UTC](https://boards.straightdope.com/t/why-arent-there-any-green-stars/385767/11 "2006-12-30T12:46:52Z")
Robert J. Sawyer’s book _Starplex_ involved a discussion of why the green star they found had to come from the future. ---
**Author:** ![FilmGeek](https://avatars.discourse-cdn.com/v4/letter/f/b19c9b/32.png) [@FilmGeek](https://boards.straightdope.com/u/FilmGeek)\ **Post date:** [December 30, 2006, 12:56pm UTC](https://boards.straightdope.com/t/why-arent-there-any-green-stars/385767/12 "2006-12-30T12:56:20Z")
[QUOTE=Ethilrist] There used to be more, but they kept getting color-corrected to light orange in post-production. [/QUOTE] Ha! You win.