Images from the 1980s show Uranus as light turquoise and Neptune as dark blue. These colors are still used today for planets on the outskirts of the Solar System. But a recently published study shows that in reality the two planets are not very different in color.
The first pictures of the pair of ice giants were taken by the Voyager 2 space probe back in the eighties. It was the first and at the same time the only probe to fly past the planets. During her mission, she took a total of 18,000 pictures. However, the scientists edited the photos of Uranus and Neptune to highlight the unique atmospheric phenomena on the planets.
This is especially true for Neptune, where they have intensified the shades of blue. Thanks to this, in the images, dark spots or a formation called the Southern Polar Wave can be seen in the atmosphere of the planet. But because of this, the planet got a blue tint, which does not correspond to reality.
In the first row, Uranus and Neptune are shown by scientists from Voyager 2 images. Below them are images from the current study. | Photo: Patrick Irwin, University of Oxford
“At the time, the artificially saturated blue was known among planetary scientists. The images were published with a caption noting it. But this note was lost over time,” he told pro BBC Patrick Irwin, a professor at the University of Oxford who was the lead researcher in the new study published by the Royal Astronomical Society.
Editing images from space is a common practice in astronomy. “You’d be foolish to look at an astronomical image and not think it’s edited. It has to be to show things,” explained Robert Massey, deputy director of the Royal Astronomical Society, to the BBC.
To capture the colors of Neptune and Uranus as accurately as possible, scientists from the University of Oxford used the Hubble Space Telescope and the Very Large Telescope in Chile. They then compared their findings with records of observations captured by the Lowell Observatory in Arizona in 1950 and 2016. The results ultimately confirmed that Uranus is slightly brighter than Neptune, mainly due to a thicker layer of aerosol haze in the atmosphere, which lightens its color.
“By applying our model to the original data, we were able to reconstruct the colors of both Neptune and Uranus as accurately as possible,” Irwin added. Unlike many drawings in textbooks, the two planets are not so different in color.
The new findings are also welcomed by astronomer Heidi Hammel, who participated in the first image of Neptune by the Voyager 2 probe in 1989. “I hope this study will help undo decades of false information about the color of Neptune,” Hammel told The New York Times.
At the same time, the study revealed what causes the hitherto mysterious seasonal color changes of Uranus, when the planet appears more green during the solstices and blue again during the equinoxes. The phenomenon is associated with the position of the planet, which almost lies on its side. Thus, in winter, one of Uranus’ poles is pointed towards the Sun and the planet appears greener, while during spring and autumn, when the Sun is above the equator, it appears more blue.
2024-01-11 16:06:11
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