JAN 08, 2024 10:35 AM PST

Revealing the True Colors of Neptune and Uranus: A Breakthrough Study

In space, not everything is how it seems, and this might be the case with Uranus and Neptune, as a study scheduled to be published in February 2024 in the Monthly Notices of the Royal Astronomical Society examines how the colors of the two gas giants might be more similar that what NASA’s Voyager 2 spacecraft imaged in 1986 and 1989, respectively, as it flew past the gas giants during its mission. Originally, Voyager 2 imaged Uranus to exhibit a greenish-type color while Neptune appeared to be a strong blue, and this new study holds the potential to help scientists better understand how to estimate the true colors of planets throughout the cosmos.

“Although the familiar Voyager 2 images of Uranus were published in a form closer to ‘true’ color, those of Neptune were, in fact, stretched and enhanced, and therefore made artificially too blue,” said Dr. Patrick Irwin, who is a Professor of Planetary Physics at the University of Oxford and lead author of the study. “Even though the artificially-saturated color was known at the time amongst planetary scientists – and the images were released with captions explaining it – that distinction had become lost over time.”

For the study, the researchers used data obtained from the Lowell Observatory in Flagstaff, Arizona, between 1950 and 2016 and supplemental data obtained from NASA’s Hubble Space Telescope between 2016 and 2022 to determine that both Uranus and Neptune exhibit similar greenish-blue colors, with Neptune being slightly bluer than Uranus, which the team attributes to the planet’s possessing a thinner haze layer than Uranus. Additionally, the team might have also determined the color changes that Uranus experiences throughout its 84-year orbit, which they attributed to occurring during the planet’s equinoxes, when sunlight is directly over Uranus’ equator. When this happens, Uranus exhibits a slightly bluer color than during the rest of its orbit.

Credit: Patrick Irwin

“The misperception of Neptune’s color, as well as the unusual color changes of Uranus, have bedeviled us for decades. This comprehensive study should finally put both issues to rest,” said Dr. Heidi Hammel, who is the executive vice president of the Association of Universities for Research and Astronomy (AURA) and is a decades-long expert on Uranus and Neptune but was not involved in this study.

This study comes at a time as several missions have been proposed to send spacecraft back to Uranus, most notably with a mission to Uranus being recommended in NASA’s 2023-2032 Planetary Science Decadal Survey.

What new discoveries will astronomers make about Uranus and Neptune in the coming years and decades? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!

Sources: NASA, NASA (1), Monthly Notices of the Royal Astronomical Society, NASA (2), EurekAlert!, National Academies 

About the Author
Master's (MA/MS/Other)
Laurence Tognetti is a six-year USAF Veteran who earned both a BSc and MSc from the School of Earth and Space Exploration at Arizona State University. Laurence is extremely passionate about outer space and science communication, and is the author of "Outer Solar System Moons: Your Personal 3D Journey".
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