Jupiter tries the sans-a-belt look

• Jupiter

These two photos, taken by Australian amateur astronomer Anthony Wesley, show the dramatic fading of Jupiter’s South Equatorial Belt from a year ago. The north belt near the top of the planet remains dark and easy to see in a small telescope. The red oval is the Great Red Spot, a hurricane-like weather system some 2 1/2 times the size of the Earth.

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DULUTH - Intrepid sky watchers with small telescopes may want to consider making an early morning pilgrimage to Jupiter, king of the planets, to see Jove’s new makeover.

Last winter changes were already under way as the South Equatorial Belt, one of the two most prominent dark “stripes” on the planet, began to fade. Most years, Jupiter sports two obvious dark gray bands, the North and South Equatorial Belts. These and Jupiter’s other belts are separated by lighter-colored zones, giving it a striped appearance.

Both belts and zones are composed of ammonia ice crystals, which freeze out at 108 degrees below zero, a temperature easily attainable at Jupiter’s half-billion- mile distance from the sun. Materials like sulfur and phosphorus mixed in with the ammonia are believed responsible for creating the clouds’ curious red, brown and yellow tints.

The origin of the belts and zones is hidden deep below the planet’s atmosphere. Bubbles of warmer air rise to the upper atmosphere and condense into clouds where they’re blown into alternating bands by 350-plus mile per hour winds.

Jupiter’s rapid rotation is at the source of its ferocious winds — a day on the planet whisks by in just

9.9 hours. This speedy spin coupled with Jupiter’s gaseous nature is also the reason the planet is flattened like a squashed meatball instead of being more nearly spherical.

So here’s the surprise. That bad boy South Equatorial Belt has completely faded away. Point your scope at the planet any morning soon and you’ll see only one obvious dark stripe, the north belt. Jupiter with only one belt is almost as odd as seeing Saturn when its rings are edge-on and invisible for a time — it just doesn’t look right.

The SEB is one of the most active areas on the planet for weather changes. Every three to 15 years, the belt, which is normally dark reddish-brown in color and often divided in two by the south equatorial belt zone, fades from view. After some weeks or months, a brilliant white spot forms within that zone and begins spouting dark blobs of material which get stretched into filaments and ovals by Jupiter’s fierce winds to create a new SEB. The big question is when the familiar belt will return. A few weeks? Months? No one can say for sure when Jupiter will once again present its familiar dual “tire track” appearance through a telescope.

Point your telescope at the planet in the next few weeks. Later this season, if Jupiter gets its stripe back, you’ll be able to appreciate how quickly a celestial object like a planet can change. It’s one of the reasons amateur astronomers observe them as often as they can, much to their spouses’ amusement.

To find Jupiter, go out about an hour before sunrise, stretch out your arm and look about one fist above the east-southeast horizon. It’s the only bright “star” you’ll see in that part of the sky.

Bob King is the News Tribune photo editor and an amateur astronomer.

Tags: state and region, astronomy