I Knew: But the detailed explanation helps

Have you ever wondered why there are no green stars?  A good educated guess is that it’s related to the narrow spectrum of visible light, that green is in the middle of the red, green, blue spectrum which together makes white light.  But this video gives a more detailed and comprehensible explanation of the science that the layperson can understand.


Where he lost me was when he hypothesized about how a star could appear green: an alien intelligence using “Dyson spheres” and “building a green filter around a star as a beacon” to attract attention.  But why create massive constructions when radio signals would be easier and detectable much further away?  Otherwise, it’s worth fifteen minutes (except for the ad from 5:20 to 6:20).



  1. Callinectes says

    This reminds me of a science/art project I was once working on with some on-line friends charting the evolutionary history of an alien planet. I received feedback on an image of the Hadean-epoch planet that mentioned that the colour of the stars I chose was fine, which I queried because they were coloured normally. I then learned that the stylistic decision had been made to depict the stars in this world’s sky as green. I challenged this as being impossible (I didn’t know exactly why other than that I was imagining a graph very much like the Planck’s Law curve in this video) and I then learned that the plan was that an alien civilisation had spread across the galaxy wrapping up systems in Dyson Spheres that made the stars appear green, but that so early on in our world’s history (as depicted in my drawing) that perhaps this had not happened yet.

    I have no idea when everyone discussed this or why I was not involved in the decision, but I just shrugged and got on with it.