The true colors of Uranus and Neptune Options

[MarcF]

An interesting new study reveals the true colors of ice giants. It appears that Neptune’s true color is a pale greenish-blue similar to that of Uranus, contrary to popular images that show it to be a much deeper shade of blue. Uranus is slightly whiter. Ultimately, Neptune has a thinner layer of haze, allowing more sunlight to reach deeper in the atmosphere. At such depth, it can be absorbed by methane gas, which soaks up red light – making the planet appear ever so slightly more blue. The presence of amassed methane ice particles may also explain why Uranus changes its color slightly during its 84-year orbit around the sun.
https://www.space.com/uranus-neptune-simila...oyager-2-images



Best wishes for 2024
Marc

PS: See also: https://theconversation.com/how-we-discover...n-colour-220244

[fredk]

Perhaps the dimmer illumination at Nepture affects the perceived colour? Uranus, at roughly 2/3 Neptune's distance from the sun, would be something like 2 1/4 times more brightly illuminated.

They should also be viewed at similar elevation angles (or at least with both high enough to avoid significant low-elevation reddening) and ideally using the same equipment.

[StargazeInWonder]

Evergreen information on this topic – There is no such thing as "true color" in the sense that lots of people seem to think, at least not when you think that it can be coded into an image and the image will possess true color in some objective sense, irrespective of how it will be displayed later (on one monitor, another, printed on paper and viewed in whatever light is falling on the paper). Look at photos of moon rocks from Apollo (or see them in a museum) and look at the Moon in the night sky and there's no comparison whatsoever – when you don't control for luminosity, "color" loses meaning. (And it's not just a matter of one moon rock or another not being representative – none of them have the silvery glow of the Moon in the night sky.)

Sunlight, and things lit by sunlight are, at Earth's distance from the Sun, far brighter than any computer monitor. As an interesting coincidence, Uranus illuminated by the Sun at its distance is about the luminosity that one experiences on a typical computer monitor display, so it is in principle possible to cue up some pixels on a monitor at the true luminosity and therefore color of Uranus and Neptune – it is not possible to do that with Saturn or anything interior to Saturn (unless the albedo of the surface in question is very low).

That said, even if there's no perfect right answer, there are certainly parameters of objectivity here and it's provocative to assert that Uranus and Neptune are about the same. Through a telescope, they don't look the same, although you need a lot of light gathering to make a fair assessment of Neptune's color.