A scientific study finds out why Uranus and Neptune have different colors

A study by researchers using observations from NASA / ESA’s Hubble Space Telescope, Gemini North Telescope, and NASA’s Infrared Telescope Facility helps explain why Uranus and Neptune have different colors.

The report, published by ESA (European Space Agency), specifies that the researchers have developed a single atmospheric model that coincides with the observations of both planets. The model reveals it excess haze on uranus accumulates in the slow, stagnant atmosphere of the planet e makes a lighter shade of Neptune appear.

Neptune and Uranus have much in common: similar masses, sizes and atmospheric compositions. But their appearance is noticeably different. At visible wavelengths, Neptune has a deep and intense blue huewhile Uranus has a decidedly pale tinge of cyan. Astronomers now have an explanation of why the two planets have different colors.

The “haze” factor.

The report states that the new research suggests that a concentrated haze layer present on both planets is thicker on Uranus than on Neptune and thus “whitens” the appearance of Uranus more than that of Neptune. If there was no haze in the atmospheres of Neptune and Uranus, both it would look almost equally blue as a result of the scattering of blue light in their atmospheres.

To reach this conclusion, an international team led by Patrick Irwin, professor of Planetary Physics at Oxford University, has developed a new system for describing the aerosol layers in the atmospheres of Neptune and Uranus. Previous investigations into the upper atmospheres of these planets had focused on the appearance of the atmosphere only at specific wavelengths.

However, this new model is made up of multiple atmospheric layers and corresponds to observations of both planets over a wide range of wavelengths. The new model also includes haze particles within deeper layers that were previously thought to contain only methane and hydrogen sulfide ice clouds.

“This is the first model that simultaneously adapts observations of sunlight reflected from ultraviolet wavelengths to near infrared wavelengths,” explained Irwin, who is the lead author of an article presenting this result in Journal of geophysical research: planets. He is also the first to explain the visible color difference between Uranus and Neptune.

The team’s model consists of three layers of aerosols at different heights. The key layer that affects the colors is the middle layer, which is a layer of haze particles. The team suspects that, on both planets, methane ice condenses on particles in this layer, drawing particles deeper into the atmosphere in a rain of methane snow.

Since Neptune has a more active and turbulent atmosphere than Uranus, the team believes that Neptune’s atmosphere is more efficient at lifting methane particles into the haze layer and producing this snow. This removes more haze and keeps Neptune’s haze layer thinner than Uranus, resulting in Neptune’s blue color appearing stronger.

To create this model, Irwin’s team analyzed archival data for several years from NASA / ESA’s Hubble Space Telescope and integrated it with data from ground-based telescopes: a series of new observations from the Gemini North Telescope and data from the Hubble Space Telescope NASA’s infrared telescope, both located in Hawaii.

Hubble offers excellent views of the peculiar atmospheric storms shared by both planets, known as “dark spots,” that astronomers have been aware of for many years. It was not known exactly which atmospheric layers were disturbed by dark spots to make them visible to Hubble. The model the team produced explains what gives the spots a dark appearance and why they are easier to detect on Uranus than on Neptune, the European Space Agency report says.