Uranus and Neptune are the two outermost planets in the solar system that we know as ice giants. They differ from other planets in their unusual structure, atmosphere, and rotation. But what color are these planets? And why does it change depending on the time of year?
We often see pictures of Uranus and Neptune. Telescopes and spacecraft take these pictures. The colors we see in the pictures are shades of blue and green. The pictures we see of planets might not show their real colors. They come from data gathered in different wavelengths.
A recent study by Professor Patrick Irwin of the University of Oxford and his colleagues found that Uranus and Neptune are similar shades of greenish-blue. However, Neptune is slightly bluer due to its atmosphere’s thin layer of haze.
Contrasts should become clearer.
Neptune has a similar hue to Uranus. To determine the true color of the planets, scientists used data from the Hubble Space Telescope and the European Southern Observatory’s Very Large Telescope, which provide spectra of every pixel in the image. In this way, they could balance composite color images recorded by Voyager 2 in the 1980s and by the Hubble Space Telescope’s Wide Field Camera 3.
It turned out that Uranus and Neptune’s color depends on the methane content in their atmospheres, which absorbs red light and reflects blue and green.
Create clarity
“Planetary scientists knew that it was an artificially saturated color, and it was also described in the captions, but this difference was lost over time,” says study leader Patrick Irwin. The new study aims to clarify the planets’ actual appearance. An explanation has also been found for why Uranus changes color depending on the season.
Uranus is sometimes greener, sometimes bluer
Uranus is the most unusual planet in the solar system because it rotates almost on its side, with its poles alternately pointing towards the sun and then away from it. This means Uranus has very long seasons where one pole is illuminated, and the other is in shadow.
Scientists have discovered that the color of Uranus changes depending on the season. When the solstice occurs, that is, summer or winter at one of the poles, Uranus becomes greener because a “hood” of icy fog consisting of methane particles forms at the pole facing the sun. This fog increases the reflection of green and red light, making the planet appear brighter.
When the equinox occurs, spring or autumn, on Uranus, the planet turns bluer because the fog clears, and the methane in the atmosphere absorbs more red light, making the planet darker.
What color is Neptune?
- Neptune is mostly a shade of greenish-blue, similar to Uranus. However, Neptune leans slightly more towards the blue side because of its atmosphere’s thin layer of haze. So, both planets share a common color palette, with Neptune having a touch of blue.
What color is Uranus?
- Uranus is mostly a greenish-blue color, similar to Neptune. However, it can appear greener or bluer depending on its seasons. When one pole faces the sun, it gets greener due to icy fog reflecting light. During the equinox, it turns bluer as the fog clears and absorbs more red light.