New images reveal the true colors of Uranus and Neptune

True colours Planets Uranus and Neptune, which often appear in images with very different colors, may actually look relatively similar, according to new research that upends everything we thought until now.

The first detailed images of the two icy planets on the edge of our solar system were obtained by NASA's Voyager 2 mission, which took images of Uranus in 1986 and Neptune in 1989. CNNIt remains the only spacecraft to pass near these two planets.

Image source: University of Oxford

New detection of the two planets

So far, Uranus has appeared to be a light blue color, while Neptune has been depicted in a striking, deep blue color. Voyager 2 took images of each planet in separate colors, and the monochrome images were combined to create composite images. Images of Neptune have been enhanced to show the white clouds and winds of the planet's atmosphere.

For his part, Patrick Irwin, professor of planetary physics at Oxford University and author of a new study on images of Uranus and Neptune, said in a related statement: “Although known images of Uranus from Voyager 2 were published closer to the ‘true’ color, Neptune’s colors were actually improved.” They are therefore artificially blue.Although the artificially saturated color was known to scientists at the time – and images were produced with captions explaining it – this distinction has been lost over time.

In fact, the Hubble Space Telescope's Spectrograph Imager and the Very Large Telescope's Multi-Unit Spectrograph Explorer capture a continuous spectrum of colors, resulting in better color accuracy. Patrick Irwin and his team applied the data collected using these instruments to the original Voyager 2 images. Corrected images show that Neptune and Uranus have a similar blue-green hue. Both planets have atmospheric haze, but Neptune appears slightly bluer because it has a thinner layer of haze.

“By applying our model to the original data, we were able to recreate the most accurate colors of both Neptune and Uranus,” Patrick Irwin said.

The team's findings and new image, published Thursday (04/01) in the Monthly Notices of the Royal Astronomical Society, not only answer a long-standing question about icy planets, but also pave the way for a better understanding. Of these two mysterious celestial bodies, researchers say.

The colors of the sky change

Meanwhile, the research team took the opportunity to answer another question: Why does the planet Uranus appear to change colors as it orbits around the Sun, as seen in the following video created by the University of Oxford?

A year on Uranus lasts 84 Earth years. While the planet appears greenest during the summer and winter solstices, it is bluest during the equinoxes. The unusual space giant rotates on its side so that one of the planet's poles points toward Earth and the sun during solstices.

By comparing images of Uranus for the study, the researchers looked at measurements of the planet's brightness taken by Lowell Observatory in Arizona from 1950 to 2016.

The team developed a model that compared light data from polar regions versus the tropics, and found that polar regions are more reflective of green and red wavelengths of light. This model included the addition of a denser haze of methane ice, which was observed as the planet moved from equinox to solstices.

“In this way, we demonstrated that the sky is greener at the solstice because the polar regions have a lower abundance of methane, but also an increase in the thickness of strongly dispersed methane ice particles,” Patrick Irwin said.

doctor. Heidi Hamel, vice president of science at the Consortium of Universities for Research in Astronomy, has spent decades studying the icy giants of space. In fact, although he was not involved in the aforementioned study, he said: “Misunderstandings of Neptune's color, as well as Uranus' unusual color changes, have plagued us for decades. This comprehensive study should put both issues to rest.”