For a long time, the color attributed to Neptune was an intense sky blue, while Uranus leaned more toward green. Thanks to the work of a team of scientists, we now have the most accurate representation of their appearance to date.
Our solar system consists of eight planets with different color combinations. We know these nuances thanks to images taken by ground-based or space telescopes. However, the images we find on the Internet are often filtered or digitally processed to reveal the nuances and characteristics of these planets. Recently, scientists conducted a comparative study aimed at accurately identifying the color of the twins Uranus and Neptune, known as the two blue planets in the solar system. To everyone's surprise, the results were published on January 4, 2024 in Royal Astronomical Society It suggests that these twins have much more in common than we thought.
Neptune is not as blue as we thought
Even today, it was taken for granted in the collective consciousness that Neptune was a deep sky blue. Why ? In the summer of 1989, NASA's Voyager 2 space probe provided the first images of this giant icy planet via radio transmission. But these early images did not provide a faithful representation of reality. in statementA person named Patrick Irwin, a physicist and professor at Oxford University who led this study, explains that Neptune’s colors were ““It has been highlighted and improved.” To highlight its details and engravings, in particular.Its clouds, its ribbons and its winds. The result: the farthest known planet in the solar system was artificially turned blue. Although these edits were initially pointed out in the comments on the photos, they were gradually forgotten.
Uranus is paler than its Gemini
To correct this misconception and redefine Neptune's true color as accurately as possible, scientists used modern data. The ones he got STIS imaging spectrometer It was placed on the NASA-designed Hubble Space Telescope and the second generation 3D Wide Field Spectrometer (MUSE for short). European Southern Observatory (ESO) in Chile. Thanks to the processing capabilities of these state-of-the-art instruments, the team was able to re-process images recorded in the 1980s by Voyager 2 and thus re-balance the recorded colors. ““This revealed that Uranus and Neptune are actually fairly similar shades of teal.”we are still reading in this press release. The main difference is that Uranus is slightly paler than Neptune due in part to the lower abundance of methane in the upper atmosphere, which absorbs more light from the Sun.
Explaining the color differences of Uranus
This study also allows us to better understand why Uranus regularly changes color during its 84-year orbit around the Sun. Professor Irwin explains that it appears greener during the solstices, i.e. in winter and summer, and this is particularly due to lower methane levels in the polar regions. Conversely, it is slightly bluer during the equinox, when the sun rises above the equator. Experts explain this seasonal difference in colors by the unusual rotation of Uranus. “It turns almost sideways during its orbit, meaning that during the planet's solstices, its north or south pole points almost directly toward the Sun and Earth.“, enlighten researchers.
This study, the first to explain why Uranus changes color during its orbit, also highlights the importance of these two planets for future space missions. “ShExploring the Uranus system – from its strange seasonal atmosphere to its diverse collection of rings and moons – is a top priority for space agencies in the coming decades.“, we learn from Professor Lee Fletcher, a planetary specialist at the University of Leicester and co-author of the new study.
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