NOIRLab/Hubble: Why Uranus and Neptune Are Different Colors

Find out the latest thinking about our universe.
User avatar
bystander
Apathetic Retiree
Posts: 21027
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

NOIRLab/Hubble: Why Uranus and Neptune Are Different Colors

Post by bystander » Wed Jun 01, 2022 2:16 pm

Multiple Observations Help Explain Why
Uranus and Neptune Are Different Colors

NOIRLab (NSF/AURA) | Hubble (NASA/ESA) | 2022 May 31
Astronomers may now understand why the similar planets Uranus and Neptune are different colors. Using observations from the Gemini North telescope, the NASA Infrared Telescope Facility (IRTF), and the Hubble Space Telescope, researchers have developed a single atmospheric model that matches observations of both planets. The model reveals that excess haze on Uranus builds up in the planet’s stagnant, sluggish atmosphere and makes it appear a lighter tone than Neptune.

Neptune and Uranus have much in common — they have similar masses, sizes, and atmospheric compositions — yet their appearances are notably different. At visible wavelengths Neptune has a distinctly bluer color whereas Uranus is a pale shade of cyan. Astronomers now have an explanation for why the two planets are different colors.

New research suggests that a layer of concentrated haze that exists on both planets is thicker on Uranus than a similar layer on Neptune and ‘whitens’ Uranus's appearance more than Neptune’s. If there were no haze in the atmospheres of Neptune and Uranus, both would appear almost equally blue. ...

Hazy blue worlds: A holistic aerosol model for Uranus and Neptune, including Dark Spots ~ Patrick G.J. Irwin et al
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

User avatar
Ann
4725 Å
Posts: 12082
Joined: Sat May 29, 2010 5:33 am

Re: NOIRLab/Hubble: Why Uranus and Neptune Are Different Colors

Post by Ann » Sat Jun 04, 2022 5:59 am

Wikipedia wrote:

At high altitudes, Neptune's atmosphere is 80% hydrogen and 19% helium.[24] A trace amount of methane is also present. Prominent absorption bands of methane exist at wavelengths above 600 nm, in the red and infrared portion of the spectrum. As with Uranus, this absorption of red light by the atmospheric methane is part of what gives Neptune its blue hue, although Neptune's vivid azure differs from Uranus's milder cyan. Because Neptune's atmospheric methane content is similar to that of Uranus, some unknown atmospheric constituent is thought to contribute to Neptune's colour.
NOIRLab wrote:

New research suggests that a layer of concentrated haze that exists on both planets is thicker on Uranus than a similar layer on Neptune and ‘whitens’ Uranus's appearance more than Neptune’s. If there were no haze in the atmospheres of Neptune and Uranus, both would appear almost equally blue.
So it's Uranus's atmosphere that has been 'whitened" by haze, not Neptune's atmosphere that has been 'blued' by an unknown atmospheric constituent! Wikipedia, you have been had!

Ann
Color Commentator