Sky Talk November 2011: Jupiter (and Its Belt) Returns!

Brilliant Jupiter is now well-placed in the eastern evening sky and once again has a surprise in store for telescope users. As reported here last year, the giant planet lost one of its two main equatorial belts (while its famed Great Red Spot increased in prominence after being nearly invisible for some time). But the belt is back! And adding to the show are Jupiter’s four bright moons waltzing around the planet from night-to-night. All you need to see the action for yourself is a clear sky and a good telescope.

Edmund Scientifics 60mm Refractor Telescope

Even the smallest of Edmund’s telescope — its sweet little Scientifics 60mm refractor normally shows the planet Jupiter straddled with two obvious brownish belts, known as the “North Equatorial Belt” and the “South Equatorial Belt.” But last year observers were surprised to find that the latter belt had vanished while the planet was passing behind the Sun! Although there’s actually dozens of belts or bands and zones visible on the face of the planet (the larger the telescope and the more experienced the observer, the more appear) seeing the giant planet with only one major belt was a strange sight indeed. This disappearing act has happened unpredictably many times in the past (its actual cause not being fully understood by planetary astronomers) and the belt was sure to return to prominence, as it always has done. But no one could say just when.

Now we can — it’s returned, and is wider and more prominent than ever! And nestled within its border floats the Great Red Spot itself, currently appearing more orange or salmon colored than red. This huge cyclonic oval is many times the size of the Earth and rotates rapidly with the planet itself, circling it in less than 10 hours. When on the side of Jupiter facing us it can be seen in the Scientific’s 60mm refractor with its 87x eyepiece (and both the major belts as well with its 35x eyepiece). The trick is knowing when to look, because it spends much of its time around the sides or back of the planet.

Fortunately, Sky & Telescope provides a timetable of its visibility in both the magazine itself and on its web site. It also provides the times of the various satellite phenomena. These include the striking disappearances and reappearances of the moons into and out of Jupiter’s huge shadow, their passing behind the planet, and their crossing in front of it casting their inky-black shadows onto the cloudtops.

A final unrelated note: the annual Leonid Meteor Shower peaks on the evening of November 17th near 11 p.m. EST. However, the Last-Quarter Moon rises around midnight and will light up the sky, greatly reducing visibility. This is normally a rather weak shower, with rates of 10 to 20 “shooting stars” per hour seen in a dark sky. But the Leonids are the famed display that on occasion turns into a meteor storm with rates of more than 1,000 an hour — and even on rare occasions (as in the 1800’s and again in the 1960’s) 40 meteors per second! So after dark on the 17th, before the sky gets flooded with moonlight, check to see if it’s “raining stars.”

— James Mullaney
Former assistant editor at Sky & Telescope magazine & author of eight books on stargazing.