Thursday 8 February 2024

Uranus is not as boring as we thought

The conventional view of Uranus has been that its apparent surface shows few, if any, distinguishing features. The images from the Voyager 2 probe in the 1980s showed what Nasa describes as a "placid, solid blue ball".

The James Webb telescope, using infrared wavelengths rather than Voyager's visible ones, shows something else. In this light the north polar ice cap becomes visible. (Uranus, bizarrely, rotates almost at right angles to all the other planets so the north pole is, in this configuration, pointing towards us.) Some storm clouds are apparent as well, and the planet's rings show up clearly.

I've not been adding to this blog of late, so I realise I am a bit late with this as a group of photos were released by Nasa back in December 2023. The Nasa web page has copious information about the set, which includes wider field photographs (also larger than the image above).

That Nasa page doesn't give information about the wavelengths used for the image. There's a more detailed report from Scientific American, which notes that image is built using wavelengths of 1.4, 2.1, 3.0 and 4.6 microns. Since photographically, we're more used to nanometres this means 1400, 2100, 3000 and 4600 nm.

[Image credit: NASA, ESA, CSA, STScI]