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  Night Sky

Turn off or shield your outside lights downward. 
Unshielded, they ruin the night sky, annoy your neighbors, and don’t help with crime.
Keep the starry skies available to everyone.

October 2016 night sky

—Charlie Christmann


As I previously reported, NASA’s Juno spacecraft is in orbit around the largest planet in our solar system, Jupiter. Juno’s mission is to understand the atmosphere and make-up of Jupiter. You would think that after several previous missions, there would be little left to surprise anyone; but, in only its first pass over the north and south poles, Juno has already provided scientists with a few surprises.

Previous missions to Jupiter included the Pioneer 11 flyby in September 1979, Voyager 1 flyby in November of 1980, Voyager 2 flyby in August of 1981, and Galileo orbital mission which began in December of 1995. Galileo’s mission, which lasted six years longer than originally expected, was to study the Jovian rings (yes, Jupiter does have faint rings) and moons. Yet, none of these missions were able to see Jupiter’s poles; each passed by, or orbited closer to, the equatorial plane. Juno is purposefully orbiting over Jupiter’s poles and not worrying much about the moons.

In the northern region of Jupiter, astronomers at the Southwest Research Institute in San Antonio were amazed to see a lack of banding near the pole. Jupiter, in the pictures we have all seen to date, features wide bands of different colors and the Great Red Spot circulating between two of the bands. The north polar region was much bluer than expected and was filled with many smaller storms. The clouds seemed to leave shadows on lower layers indicating they are much higher in the atmosphere.

Like Earth, Jupiter has a magnetic field, which should create auroras, like we see at our north and south poles, only much bigger. In fact, radio waves generated by these auroras have been captured here on Earth. But scientists have not actually seen the southern lights on Jupiter, until now. Juno’s infrared camera caught bright and highly-structured auroras there. These will be studied in more detail as Juno makes more passes over the poles.

More surprises:

Jupiter has another surprise in the Great Red Spot. The Great Red Spot is a giant storm that has persisted since before Galileo (the astronomer) first spied it in his telescope four hundred years ago. Even though the spot is slowly shrinking, it could still easily swallow Earth. Jupiter’s atmosphere measures around 1,700 degrees Fahrenheit, except for near the poles, where the auroras heat the atmosphere, and the Great Red Spot. Its temperature reads 2,420 degrees. What could be generating that much additional heat five hundred miles above the spot?

Models of Jupiter expected to see much cooler overall temperatures since it is five time farther away from the sun than Earth and receives about one twentieth as much energy as we do—that rules out solar heating.

James O’Donoghue with Boston University’s Center for Space Physics thinks the Great Red Spot itself is to blame. He believes sound waves, very loud ones, are generated by the turbulence at the edges of the spot. Where the spot collides with the band going in the opposite direction, it creates huge vortices there which eventually release their energy as sound waves reaching above the spot. Researchers hope Juno will be able to take a closer look at the Great Red Spot and help refine their ideas. Maybe Juno can even tell us why Jupiter is hotter than predicted.

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