Jupiter ducks behind sun to remove belt

Jupiter's belt has faded and might not be back for 15 years. Pictures: Anthony Wesley

Interplanetary observers have noted that the gas giant has looked a little naked of late - it's lost one of its iconic stripes.

It's noticeable for anyone with even a "relatively small telescope", according to The Planetary Society, although what constitutes a "small telescope" for the Planetary Society doesn't necessarily mean it will fit under a Christmas tree.

Jupiter's disrobing began somewhere around June last year when the South Equatorial Belt began to fade. By May this year, it had disappeared completely, leaving only the North Equatorial Belt protecting Jupiter's modesty.

It was common knowledge that the belt was disappearing, but flirty Jupiter ducked behind the sun for three months and it was only in recent weeks that eager observers could see to what extent it's belt had vanished.

Noted Jupiter watcher Anthony Wesley - the man who discovered its "scar" last year - has tracked the disappearing belt from his Murrumbateman back yard. It's his before-and-after photos which are the most likely you'll come across on the web if you search for the phenomenon. "It was obvious last
year that it was fading. It was closely observed by anyone watching Jupiter," he said. "There was a big rush on to find out what had changed once it came back into view."

Mr Wesley said while it was a mystery as to what had caused the belt to fade, the most likely explanation was that it was linked to storm activity that preceded the change. While exciting for astronomers, it was also well-known that Jupiter lost or regained one of its belts every 10 or 15 years.

"The question now is when will the South Equatorial belt erupt back into activity and reappear?" Mr Wesley said, adding that it could be anywhere up to 15 years. Although when it happens, it would be "a matter of days or a week".

"There'll be a great planet-wide eruption of storm activity at that latitude, then the normal dark belt will appear," he said. "Nobody really knows when it will happen, but there'll certainly be a lot watching." And if you're looking for the best view of Jupiter with its pants down, Mr Wesley said it will be closest
to Earth on September 24.

"Every Jupiter-watcher has that day on their calendar," he said.