Jovial company: Our largest planetary neighbor pays a close visit

NASA’s Juno spacecraft passes in front of Jupiter in this artist’s depiction. (Nasa/JPL-Caltech)

NASA’s Juno spacecraft passes in front of Jupiter in this artist’s depiction. (Nasa/JPL-Caltech)

Jupiter came closest to Earth last weekend, and will dominate the sky all this month. As a bonus, it ascends higher up than it will again until the year 2023. So we have ideal conditions for observing this most dynamic planet in the known universe.

Jupiter is in Gemini, but you don’t need to know that or anything else to find it any night. Just look around for the very brightest star. It’s astronomy made simple. You’ll see that it floats to the upper left of Orion.


If have a small telescope and a night when the stars are not twinkling, have a look. Jupiter’s colorful features include dark belts, white zones, small dark and white circular storms and, most famous of all, its Great Red Spot. This giant hurricane, twice the size of Earth, makes one spin per week. Some years the Great Red Spot is beige, sometimes it’s brick red, but it has been orange the past few years. Nobody knows what causes the persistent color – probably sulfur or phosphorous compounds.

A giant it surely is. You could take all the other planets and double their combined masses, and you wouldn’t get the weight of Jupiter alone. The ancients got it strangely correct when they named it the king of the gods.

If you don’t have a telescope, just use steadily braced binoculars – or better still, those pricey-but-amazing Canon image-stabilized models – to see the four giant Moons, found by Galileo in 1610, which will appear as dots in a straight line like a string of pearls. In common with Mercury, Jupiter has virtually no tilt to its axis, which is why, no matter where each satellite happens to stand in its orbit, they all form a straight line from our sideways viewing angle.

An amazing new spacecraft is en route to Jupiter. The Juno machine whizzed past Earth on October 9, getting a planned gravitational boost to increase its speed to fling it precisely outward to arrive at Jupiter in July 2016. Once there, it will brake into orbit and start circling the giant planet at the astoundingly low distance of just 3,000 miles above the cloud tops.

This is dangerous. The radiation there makes the core of a nuclear reactor seem benign. Just lingering over those clouds for a minute would kill a human. Thus, all the electronics are shielded in a titanium box.

I chatted with Juno’s principal investigator Scott Bolton last week, and what he revealed was truly amazing. For example, a unique feature of Juno is its electrical supply. Instead of using RTGs – radioisotope thermoelectric generators, which are what have reliably supplied decades of electricity for every single spacecraft visiting all the planets from Mars outward – Juno has solar panels. It’s the first-ever “green” planetary probe. You can almost visualize it being crammed with chickens and aloe plants and wafting incense.

Actually the reason had nothing to do with ecology. The next-gen RTGs were supposed to be ready in time for Juno’s launch, but the engineers didn’t trust that there’d be no delays. Using solar panels in an environment where sunlight is 25 times weaker than it is here on Earth was not easy. But the entire craft needs only 100 watts to operate!

Juno will look at Jovian auroras, use its magnetometer and other instruments to ascertain what’s beneath those clouds and take high-resolution close-up images. It’s an exciting mission.

Meanwhile, look around the next clear night. Find the brightest star in the sky. And salute the largest and most dynamic world within at least four light-years of Saugerties.

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