Juno Returns A ‘Pearl’ From Jupiter

NASA’s Juno spacecraft snapped this photo of Jupiter during its last close flyby on Dec. 11. It highlights the seventh (at right) of eight features forming a ‘string of pearls’ on Jupiter — massive counterclockwise rotating storms that appear as white ovals in the gas giant’s southern hemisphere. Since 1986, these white ovals have varied in number from six to nine. There are currently eight white ovals visible. The spacecraft was about 15,300 miles (24,600 km) from Jupiter at the time. Credit: NASA/JPL-Caltech/SwRI/MSSS; reprocessed by Damian Peach

NASA’s Juno spacecraft made another of its close flybys of Jupiter on Dec. 11 and returned this new photo featuring a extraterrestrial pearl. But while a real pearl is a lustrous gem built around an irritant such a food particle in a mollusk, this pearl is a storm half the size of the Earth whirling counterclockwise in Jupiter’s upper atmosphere. Its picturesque clouds are composed largely of ammonia ice crystals ‘chillin’ at 190° below zero Fahrenheit (–125° C).

Jupiter on Dec. 10, 2016 displays multiple clouds belt and zones (white bands), the Great Red Spot and four of the 8 ‘pearls’ in the planet’s South Temperate Belt below the Red Spot. The moon Ganymede is seen at lower left. Credit: Christopher Go

The pearl is but one in a string of eight in the gas giant’s southern hemisphere. Storms on Earth have lifetimes numbered in days and weeks, Jupiter’s can last for decades, even centuries. Since 1986, these white ovals have varied in number from six to nine. A few years back, several merged to form one larger, ruddy-colored storm that resembled a miniature version of the Great Red Spot nicknamed Red Spot Jr. There are currently eight white ovals visible, and they girdle the planet’s southern hemisphere.

Juno will makes 36 close flybys of Jupiter during its mission. Notice that it only spends a very short time close to the planet due to the dangerous radiation environment there, represented by the multicolored ovals on either side of the planet. Credit: NASA

Juno orbits the giant planet in a highly elongated (very oval-shaped) orbit and takes its most detailed photos and gathers essential data when it’s closest to the planet. Then it swings back out in a giant loop, slowing down while relaying the its data booty to Earth. When closest, the probe is speeding along at 129,000 mph (60 km/second). Good thing it gets out of there in hurry because it’s during these close brushes that the spacecraft is also most at risk from the maelstrom of high-speed atomic particles whipped around by Jupiter’s powerful magnetic field. To protect Juno’s instruments from harm, most of the electronics are shielded in a ~1/2 thick titanium vault.

Jupiter is the only bright planet at dawn. You’ll see it nicely placed in the southern sky in late December around the start of dawn. Spica lies just to its south. Stellarium

Its next close flyby happens on Feb. 2, 2017. While Juno’s performing its loop de loop, you can always picture the action in your mind’s eye any clear morning around dawn. If you’re up around 6:30-7 a.m. face to the south-southeast, and you’ll see two bright “stars” paired together about halfway between the horizon and overhead point. The top one, much brighter, is Jupiter. Below it twinkles Spica, Virgo’s brightest star. Now imagine Juno as the tiniest gnat pestering the giant planet.

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