by Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on exciting discoveries, scientific advances and more.
Often seen in images as having very different colors, the true colors of Neptune and Uranus may be more similar than previously thought, new research has found.
The first detailed view of the two ice giants at the edge of our solar system was made possible by NASA’s Voyager 2 mission, which flew by Uranus in 1986 and Neptune in 1989. Voyager 2 remains the only spacecraft to fly by both.
Uranus appeared to be a pale cyan color, while Neptune was depicted as a striking deep blue. Voyager 2 captured images of each planet in separate colors, and the single-color images were combined to create a composite. The images of Neptune have been enhanced to show the white clouds and winds of the planet’s atmosphere.
“While the famous Voyager 2 images of Uranus were published in a form closer to ‘true’ color, those images of Neptune were stretched and enhanced, and thus artificially rendered too blue,” said Patrick Irwin, professor of planetary physics. at the University of Oxford and author of a new study about the images, in a statement.
“Although the artificial saturated color was known to planetary scientists at the time – and the images were released with captions explaining – that distinction has been lost over time.”
The Hubble Space Telescope’s Imaging Spectrograph and the Very Large Telescope’s Multi-Unit Spectroscopic Probe instrument capture a continuous spectrum of colors, resulting in better color accuracy. Irwin and his team applied data collected using those instruments to Voyager 2’s original images.
The corrected images show that Neptune and Uranus have the same blue-green color. Both planets have an atmospheric cloud, but Neptune appears slightly cloudier because it has a thinner cloud layer.
“Applying our model to the original data, we were able to reproduce the most accurate representation yet of the color of both Neptune and Uranus,” Irwin said.
The team’s findings and the new image, published Thursday in the Monthly Notices of the Royal Astronomical Society, not only address a long-standing question about the ice giants, they pave the way for a better understanding of the enigmatic planets, researchers say. .
Shifting colors of Uranus
While solving one planetary mystery, the research team took the opportunity to answer another: why Uranus appears to change colors as it orbits the sun, as seen in the video loop below.
A year on Uranus lasts 84 years on Earth. Although the planet appears greener during the summer and winter solstice, it is more bluish during the equinoxes.
The unusual earth turns on its side, so one of the planet’s poles points toward Earth and the sun during solstices.
In comparing images of Uranus for the study, the researchers looked at brightness measurements of the planet recorded at the Lowell Observatory in Arizona from 1950 to 2016.
The team developed a model that compares light data from the polar regions versus the equatorial regions and found that the polar regions are more reflective in green and red wavelengths of light. This model involved the addition of a gradually thickening “hood” of Nebula made of methane ice, seen when the planet transitions from perihelion to solstice.
“In this way, we have shown that Uranus is greener at the solstice due to the reduced abundance of methane at the polar regions and the increased thickness of diffuse methane ice particles,” Irwin said.
Dr Heidi Hammel, vice president of science at the Association of Universities for Research in Astronomy, has spent many years studying the ice giants.
“The misunderstanding of Neptune’s color, as well as the unusual color changes on Uranus, have plagued us for years,” Hammel, who was not involved in the study, said in a statement. “This comprehensive study should put both issues to rest.”
Investigating an ice giant
Many mysteries remain about the ice giants. The James Webb Space Telescope recently revealed a new portrait of Uranus that revealed its often invisible rings and hidden elements of its atmosphere.
In recent years, researchers have detected X-rays from Uranus. Scientists also found a strange “blip” in the Voyager 2 data that would indicate the spacecraft flew through a plasmoid, a giant magnetic bubble that broke off part of the planet’s atmosphere and floated out into space.
“A mission to explore the Uranian system – from its peculiar seasonal atmosphere, to the diverse collection of rings and moons – is a high priority for the space agencies in the coming years,” said study co-author Leigh Fletcher, a planetary scientist at the Centre. The University of Leicester, in a statement.
“Global studies like this, which show how the appearance and color of Uranus have changed over many years in response to the most peculiar seasons in the Solar System, will be crucial to putting the discoveries of this future mission into a wider context.”
For more CNN news and newsletters create an account at CNN.com
