4 ms·

Some stars, eg Lambda B, do appear green when looking thru amateur telescopes.

adrian_b 2y ago
Most likely they appear blue-green (a.k.a. turquoise a.k.a. teal), not green. As another poster has mentioned, with increasing temperatures the color sequence for a black body is black => red => yellow => white => blue-green => blue. Neither the greenish colors intermediate between yellow and blue-green nor the purplish colors intermediate between red and blue can appear as colors of a hot body, but only the colors that can be seen when low-pass filtering white light (i.e. between red and yellow, inclusive) or when high-pass filtering white light (i.e. between blue-green and blue, inclusive). While above I have simplified by saying that purplish colors should not appear, that is only partially true, because very hot stars could appear as violet, i.e. reddish blue, due to the defect of human vision that the red photoreceptors are sensitive not only to red light, but also to light with a higher frequency than where the maximum sensitivity for blue is, so the high-frequency violet light excites both the blue and the red photoreceptors, being indistinguishable from a mixture of blue light with low-frequency red light. With a video camera where the output signals would not be processed in such a way as to mimic the bugs of human vision (like in all normal color video cameras), purplish colors would not be obtained for hot bodies.
- amenghra 2y ago
  When you have double (or more) stars and gases involved, you can end up with a green-ish tint. Obviously, different people will describe the color in a different way due to everyone's own seeing conditions, instruments, and color sensitivity.
  - adrian_b 2y ago
    Oxygen has a strong green emission, so gases rich in oxygen may appear green, which is why many nebulae are green, like also most auroras in the Earth's atmosphere. Therefore indeed a star behind gas rich in oxygen may appear green, but that green light comes from the gas, not from the star.

Most likely they appear blue-green (a.k.a. turquoise a.k.a. teal), not green. As another poster has mentioned, with increasing temperatures the color sequence for a black body is black => red => yellow => white => blue-green => blue. Neither the greenish colors intermediate between yellow and blue-green nor the purplish colors intermediate between red and blue can appear as colors of a hot body, but only the colors that can be seen when low-pass filtering white light (i.e. between red and yellow, inclusive) or when high-pass filtering white light (i.e. between blue-green and blue, inclusive). While above I have simplified by saying that purplish colors should not appear, that is only partially true, because very hot stars could appear as violet, i.e. reddish blue, due to the defect of human vision that the red photoreceptors are sensitive not only to red light, but also to light with a higher frequency than where the maximum sensitivity for blue is, so the high-frequency violet light excites both the blue and the red photoreceptors, being indistinguishable from a mixture of blue light with low-frequency red light. With a video camera where the output signals would not be processed in such a way as to mimic the bugs of human vision (like in all normal color video cameras), purplish colors would not be obtained for hot bodies.

amenghra 2y ago
When you have double (or more) stars and gases involved, you can end up with a green-ish tint. Obviously, different people will describe the color in a different way due to everyone's own seeing conditions, instruments, and color sensitivity.
- adrian_b 2y ago
  Oxygen has a strong green emission, so gases rich in oxygen may appear green, which is why many nebulae are green, like also most auroras in the Earth's atmosphere. Therefore indeed a star behind gas rich in oxygen may appear green, but that green light comes from the gas, not from the star.