The True Color of Neptune: It’s Not as Blue as Previously Believed

Neptune's true color is a pale greenish-blue similar to that of Uranus, contrary to popular belief that it is a much deeper blue.

NASA's Voyager 2 spacecraft passed by the outer planet in the 1980s and sent back photos showing the strikingly different colors of Uranus and Neptune.

This is puzzling given their similar size, mass, and chemical composition. Models of the planet's atmosphere can explain some of the fluctuations, such as Uranus' thicker “haze layer” that reflects more white light and makes the planet appear brighter, but these may explain why the planet is It doesn't fully explain why you should have something like that. different shades.

now, Patrick Irwin Researchers at the University of Oxford have processed images from Voyager 2 to show what the planet looks like to the human eye.

The original photo of Neptune taken by Voyager 2 had an enhanced contrast ratio to highlight hard-to-see atmospheric features. In addition to how they balanced the colors to create the final composite image, this also made the planet appear bluer.

Scientists at the time knew this and included these changes in photo captions, but over time the captions became detached from the images and Neptune's deep blue hue became a fact in the public consciousness. According to Irwin, the shrine is now enshrined inside.

He and his team developed a model that uses shots taken by the Hubble Space Telescope to convert raw image data into true-color images. This image contains more complete information about the light. This produced similar hues on both planets. “The way the eye works makes true-color images much more boring and bland,” Irwin says.

The researchers also used Hubble images and images from the Lowell Observatory in Arizona to build a model to predict how Uranus' color would change during its long 84-year orbit around the sun. Due to the rotation of the planet, more of the equator is visible at the vernal equinox, and more of the poles are visible at the summer solstice. At the equator, there is more methane and red light is absorbed. The planet also has a hood of reflective, brightening ice particles that forms at its sun-facing poles during the equinoxes, increasing the reflectance of red and green wavelengths.

This helps explain the long-standing mystery of why Uranus appears slightly green on the summer solstice. “We knew there was a hood, we knew there was less methane in the polar regions, but no one had put it all together to be able to explain what was really going on seasonally. “It was,” Irwin said.