Using ESO’s Very Large Telescope (VLT), astronomers have observed a large dark spot in Neptune’s atmosphere, with an unexpected smaller bright spot adjacent to it. This is the first time a dark spot on the planet has ever been observed with a telescope on Earth. Read more in the ESO press release here.
Image: © ESO/P. Irwin et al.; This image shows Neptune observed with the MUSE instrument at ESO’s Very Large Telescope (VLT). At each pixel within Neptune, MUSE splits the incoming light into its constituent colours or wavelengths. This is similar to obtaining images at thousands of different wavelengths all at once, which provides a wealth of valuable information to astronomers. The image to the right combines all colours captured by MUSE into a “natural” view of Neptune, where a dark spot can be seen to the upper-right. Then we see images at specific wavelengths: 551 nanometres (blue), 831 nm (green), and 848 nm (red); note that the colours are only indicative, for display purposes. The dark spot is most prominent at shorter (bluer) wavelengths. Right next to this dark spot MUSE also captured a small bright one, seen here only in the middle image at 831 nm and located deep in the atmosphere. This type of deep bright cloud had never been identified before on the planet. The images also show several other shallower bright spots towards the bottom-left edge of Neptune, seen at long wavelengths.
Imaging Neptune’s dark spot from the ground was only possible thanks to the VLT’s Adaptive Optics Facility, which corrects the blur caused by atmospheric turbulence and allows MUSE to obtain crystal clear images. To better highlight the subtle dark and bright features on the planet, the astronomers carefully processed the MUSE data, obtaining what you see here.