The skies belong to everyone, part three: Jupiter, Saturn, Uranus, Neptune

Posted by David Eicher
on Wednesday, May 04, 2011

So you bought a telescope to look at everything the universe has to offer. You’ve explored the various craters and maria of the Moon, and some of the planets  — Mercury, Venus, and Mars. What should you look at next?

European Space Agency
The solar system’s giant planet, Jupiter, is enormous — so huge it could hold 1,000 Earths. Jupiter is fascinating with a telescope or even with 7x binoculars. Its four brightest moons — Io, Ganymede, Europa, and Callisto (each as big as Earth’s own Moon) — line up alongside the planet. Even when viewed through binoculars, Jupiter appears as a little disk, and its four bright moons appear as little specks of light. On successive nights, check Jupiter with binoculars and you’ll discover that the four specks change positions around the planet. This is exactly what Galileo observed 400 years ago, confirming that Jupiter’s moons circle the planet just as the planets encircle our Sun.

Viewed through a small telescope, Jupiter is a memorable sight. The most prominent features are cloud bands — gigantic swirling clouds that most often appear in a variety of tawny shades moving rapidly along the planet’s creamy-white surface. But these are not the only visible features. At the right time, Jupiter’s Great Red Spot — a huge storm several times the size of Earth — is observable as a pale orange oval.

Perhaps the most striking sight in backyard astronomy is that of Saturn, the golden-orange ringed world beyond Jupiter. Binoculars show Saturn as a tiny ellipse (the rings) with a faint “star” nearby (its brightest moon, Titan), but you really need a magnification of 75x or 100x to do Saturn justice. With a small telescope, you’ll see what many first-time observers find an indescribable sight: a bright oval orange globe, perfectly encircled by pale, sharply defined rings. And Titan, along with two or three other moons, is visible if you know which speck of light to look for.

Beyond Saturn, the solar system contains two more “gas giants” — Uranus and Neptune. Although large planets, they look faint and small because of their great distance. Both are visible through binoculars, appearing as bluish-green dots distinguishable from stars only by their color and position. In a 3- or 4-inch telescope at high power, Uranus and Neptune appear as tiny disks.

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