New images reveal that Neptune and Uranus are more similar to each other than previously thought.
According to Sky News, many people think Neptune is a rich blue color and Uranus is green.
However, Professor Patrick Irwin from the University of Oxford and his team found that the two most distant ice giants in our solar system have a similar shade of greenish blue.
Experts point out that images taken in the twentieth century — including by NASA's Voyager 2 mission in the 1980s — gave rise to the idea that the two planets are different colors.
Monochrome images are then recombined to create composite color images, which are not always accurately balanced to create a true color image.
Especially in the case of Neptune, these compositions were often made very blue.
Early images of Neptune from Voyager 2 have been strongly enhanced to better reveal the shape of the clouds, bands and wind, scientists say.
Professor Irwin said: “While the familiar Voyager 2 images of Uranus were released in a form close to the 'true' color, the images of Neptune were actually stretched and enhanced, rendering them artificially blue.”
He continued: “Artificially saturated color was known among planetary scientists at the time – and pictures were published with captions explaining it – and the distinction was lost over time.”
He added: “By applying our model to the original data, we were able to reconstruct a more accurate representation of the color of both Neptune and Uranus.”
In the new study, researchers used data from spectroscopic imaging from the Hubble Space Telescope (STIS) and the Multi-Unit Spectroscopic Explorer (MUSE) at the European Southern Observatory's Largest Telescope.
In both STIS and MUSE, each pixel is a continuous spectrum, meaning that observations can be processed to determine the true apparent color of Uranus and Neptune.
The researchers used the data to reconstruct composite color images recorded by the Voyager 2 camera and the Hubble Space Telescope's Wide Field Camera 3.
However, the study also found that Neptune has a slight hint of extra blue color, which the model reveals is caused by the planet's haze layer.
The study also answers the long-standing mystery of why Uranus changes color slightly during its 84-year orbit around the Sun.
The results show how thick certain gases are at the planet's north and south poles, and how they appear when these poles are closer to the Sun.
