Something’s Munching On Jupiter’s Great Red Spot

Pepperoni in a spoon? This infrared-enhanced photo taken on May 19 shows that the swirl connecting the Great Red Spot to the South Equatorial Belt (dark belt above and left of the GRS) contains red material pulled from the Spot. Anthony Wesley

Weird things are happening around Jupiter’s Great Red Spot (GRS). The iconic red hurricane that’s been swirling around in the Jovian atmosphere for at least 350 years may be flaking away. Over the past week, winds and gases in the South Equatorial Belt (SEB) — one of two prominent, dark cloud belts striping the planet’s atmosphere — are blowing past the Spot, peeling off pieces about once a week. Some of them span up to 6,200 miles (10,000 km) across.

Jupiter on April 21, 2014 taken by the Hubble Space Telescope before this month’s “flaky” activity. NASA / ESA

Astronomers have seen “flakes” slough off the GRS before, but they’ve become more frequent of late. At the same time, the Spot has been steadily shrinking due to other factors. Currently 1.3 times the diameter of Earth, a century ago it was more than three times as wide. Winds and clouds are always blowing past the Red Spot, but this month they’re interacting with it and even altering its outline. A photo taken on May 22 by Australian amateur Anthony Wesley shows that it’s literally bent out of shape.

On May 22 the Great Red Spot’s overflowing gases from the SEB have distorted its shape. Typical wind speeds in Jupiter’s belts and zones are about 225 mph (360 kph). Anthony Wesley

Photos reveal a large, pale “moat” of clouds called the Red Spot Hollow surrounding the Spot and outlined by twin, narrow cloud belts connecting the Spot to the SEB. You might wonder if you can see any of this in a telescope. The answer is “yes!” The GRS sports a deep orange color, and both the Hollow and dark cloud filaments passing above and below it are visible in a 6-inch or larger scope in good seeing. That’s when the air is steady enough for a clear view of the planet. Other nights, Jupiter will shimmer and bounce due to atmospheric turbulence overhead. Use a magnification of between 100x and 200x for the best views.

Strong winds whip Jupiter’s clouds into alternating dark belts and bright zones. Sulfur and possibly phosphorus compounds may be responsible for the dark tone of the belts as well as the Great Red Spot. At Jupiter’s distance from the sun, ammonia exists as ice crystals.

You’ll need to know when to look, too. Because Jupiter rotates rapidly — one spin takes just under 10 hours — sometimes the Spot’s in view and sometimes hidden on the backside. It would be nice if Jupiter rose at a convenient hour. That will happen in about a month. For now, the planet first appears in the southeast around 11 o’clock local time in late May and doesn’t get high enough for a good look until around midnight. We’re going to lose some sleep here, but this is something special, so if you have a scope, go for it.

You can see how the local jet streams flow in the vicinity of the GRS as well as a remnant fragment “peeled” from the Spot. It appears that gases are flowing in some sort of loop around the Spot. Anthony Wesley

Here are Central Daylight times when the Great Red Spot faces skywatchers in the Americas. You can easily view the GRS for about 2 hours each time it transits Jupiter — that’s when it comes around to face us directly. Add an hour for Eastern Time; subtract an hour for Mountain and 2 hours for Pacific times:

May 23 — between 4:40 to 6:40 a.m.
May 24 — between 12:30 and 2:30 a.m.
May 25 — between 6:15 and 8:15 a.m.
May 26 — between 2 and 4 a.m.
May 26-27 — between 11 p.m. and 1 a.m.
May 28 — between 3:45 and 5:45 a.m.
May 28-29 — between 11:30 p.m. and 1:30 a.m.
May 30 — between 5:15 and 7:15 a.m.
May 31 — between 1:15 and 3:15 a.m.

Look for Jupiter to the left (east) of Scorpius around 11 p.m. local time this week. It’s outstandingly bright and easy to recognize. Stellarium

You can also use Sky and Telescopes GRS transit calculator. Just enter a date and you’ll get the times of the next three transits. I hope you get a chance to spot the Spot. I’ll be watching at the next opportunity. Clear (and calm) skies!

6 Responses

  1. kevan hubbard

    I was looking at Jupiter tonight but only with an 8×36 vortex monocular so no details apart from one Moon off to the right (remembering the monocular is right way up!as much as space has a right way up!). it’s very low for us ‘up north'(51.40 n.where I saw it).good view of Antares too to Jupiter’s west but similar height,think I just caught m4 a bright but diffuse globular so tricky through the thick atmosphere at higher latitudes.actually 51.4 is quite southerly for me these days I’m mainly based at about 54.60 a full 3 degrees north.

    1. astrobob

      Yes, those objects are low for me, too. I like M4 — easy in binoculars. Further south it’s visible with the naked eye.

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