Mysterious Neptune dark spot detected from Earth for the first time

Utilizing ESO’s Very Massive Telescope (VLT), astronomers have noticed a big darkish spot in Neptune’s ambiance, with an surprising smaller vibrant spot adjoining to it. That is the primary time a darkish spot on the planet has ever been noticed with a telescope on Earth. These occasional options within the blue background of Neptune’s ambiance are a thriller to astronomers, and the brand new outcomes present additional clues as to their nature and origin.

Massive spots are frequent options within the atmospheres of large planets, probably the most well-known being Jupiter’s Nice Crimson Spot. On Neptune, a darkish spot was first found by NASA’s Voyager 2 in 1989, earlier than disappearing a couple of years later. “Because the first discovery of a darkish spot, I’ve at all times puzzled what these short-lived and elusive darkish options are,” says Patrick Irwin, Professor on the College of Oxford within the UK and lead investigator of the examine.

This analysis is introduced in a paper, titled “Cloud construction of darkish spots and storms in Neptune’s ambiance,” in Nature Astronomy.

Irwin and his staff used knowledge from ESO’s VLT to rule out the chance that darkish spots are attributable to a “clearing” within the clouds. The brand new observations point out as an alternative that darkish spots are possible the results of air particles darkening in a layer under the principle seen haze layer, as ices and hazes combine in Neptune’s ambiance.

Coming to this conclusion was no straightforward feat as a result of darkish spots aren’t everlasting options of Neptune’s ambiance and astronomers had by no means earlier than been in a position to examine them in adequate element. The chance got here after the NASA/ESA Hubble House Telescope found a number of dark spots in Neptune’s ambiance, together with one within the planet’s northern hemisphere first seen in 2018.

Irwin and his staff instantly started working learning it from the bottom—with an instrument that’s ideally suited to those difficult observations.

Utilizing the VLT’s Multi Unit Spectroscopic Explorer (MUSE), the researchers have been in a position to cut up mirrored daylight from Neptune and its spot into its element colours, or wavelengths, and procure a 3D spectrum. This meant they may examine the spot in additional element than was potential earlier than. “I am completely thrilled to have been in a position to not solely make the primary detection of a darkish spot from the bottom, but in addition report for the very first time a mirrored image spectrum of such a characteristic,” says Irwin.

Since totally different wavelengths probe totally different depths in Neptune’s ambiance, having a spectrum enabled astronomers to higher decide the peak at which the darkish spot sits within the planet’s ambiance. The spectrum additionally supplied data on the chemical composition of the totally different layers of the ambiance, which gave the staff clues as to why the spot appeared darkish.

The observations additionally provided up a shock outcome. “Within the course of we found a uncommon deep vibrant cloud sort that had by no means been recognized earlier than, even from space,” says examine co-author Michael Wong, a researcher on the College of California, Berkeley, U.S..

This uncommon cloud sort appeared as a vibrant spot proper beside the bigger principal darkish spot, the VLT knowledge exhibiting that the brand new “deep vibrant cloud” was on the identical stage within the atmosphere as the principle darkish spot. This implies it’s a utterly new sort of characteristic in comparison with the small ‘companion’ clouds of high-altitude methane ice which have been beforehand noticed.

With the assistance of ESO’s VLT, it’s now potential for astronomers to review options like these spots from Earth. “That is an astounding improve in humanity’s capability to watch the cosmos. At first, we might solely detect these spots by sending a spacecraft there, like Voyager. Then we gained the power to make them out remotely with Hubble. Lastly, expertise has superior to allow this from the bottom,” concludes Wong.