Click for original Webb false-color image.
In a follow-up to a recent Hubble Space Telescope optical image of Uranus, scientists have now used the Webb Space Telescope to take a comparable picture in the infrared of the gas giant.
Both pictures are to the right, with the Webb picture at the top including the scientists’ annotations.
On the right side of the planet there’s an area of brightening at the pole facing the Sun, known as a polar cap. This polar cap is unique to Uranus – it seems to appear when the pole enters direct sunlight in the summer and vanish in the fall; these Webb data will help scientists understand the currently mysterious mechanism. Webb revealed a surprising aspect of the polar cap: a subtle enhanced brightening at the center of the cap. The sensitivity and longer wavelengths of Webb’s NIRCam may be why we can see this enhanced Uranus polar feature when it has not been seen as clearly with other powerful telescopes like the Hubble Space Telescope and Keck Observatory.
At the edge of the polar cap lies a bright cloud as well as a few fainter extended features just beyond the cap’s edge, and a second very bright cloud is seen at the planet’s left limb. Such clouds are typical for Uranus in infrared wavelengths, and likely are connected to storm activity.
The Webb image also captures 11 of Uranus’s 13 rings, which appear much brighter in the infrared than in the optical.
Unlike all other planets in the solar system, Uranus’s rotation is tilted so much that it actually rolls as it orbits the Sun, a motion that is obvious by comparing these pictures with Hubble’s 2014 optical picture.
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