The Hour of the Planets

NASA Science News
http://science.nasa.gov/headlines/y2003/21jan_planets.htm

Dashing out the door to work or school? Pause for a moment and look up. There are two dazzling planets in the morning sky.

January 21, 2003: John Steinbeck called it "the hour of the pearl."

It's "the gray time," he wrote in Cannery Row, "after the light has come and before the sun has risen--the interval between day and night when time stops and examines itself. No automobiles are running then. The streets are silent of progress and business. And the rush and drag of the waves can be heard as they splash in among the piles of the canneries."

That was 50 years ago. Nowadays the hour of the pearl is announced by ringing alarm clocks. It's when you drag yourself out of bed, rush to get dressed, grab a hasty breakfast. And what's that distant roar? The sound of the freeways.

So let's call it something different: "The hour of the planets."

There are two bright ones in the dawn sky this month: Venus and Jupiter. Even after all the other stars and planets have begun to fade against the brightening sky, these two are absolutely eye-catching. And it only takes a moment to enjoy them as you dash out the door to work or school.

First, glance toward the southeast in the direction (more or less) of the rising sun, and you'll spot Venus (magnitude -4.4) shining 140 times brighter than a first magnitude star. Venus is often mistaken for a UFO or a landing airplane, but it you pause for a long look, you'll see that it doesn't move like either of those. It's as still as the morning streets of Cannery Row. (Actually, Venus does move; it rises slowly like the Sun. Keep an eye on it from dawn onward. If you know where to look, you can see Venus in broad daylight.)

Next, spin around and look west. There's Jupiter (magnitude -2.4), about the same distance above the horizon as Venus is. Although Jupiter is much bigger than Venus, it is 6 times farther away from Earth and correspondingly dimmer. Even so, Jupiter is 25 times brighter than a first magnitude star--very impressive.

If you do have time to spare, and a small telescope, take a closer look at Jupiter and Venus.

Jupiter is very rewarding. You'll be able to see its rust-colored cloud belts with ease. First-time observers often note that the planet looks squashed--wider along the equator than between the poles. Is there something wrong with the telescope? No. Jupiter really is flattened. Although Jupiter is 70 times bigger around the middle than Earth, it spins more than twice as fast; a day on Jupiter lasts only 9 hours and 55 minutes. This rapid spin is what gives Jupiter its equatorial bulge. Small telescopes will also reveal up to four "stars" around Jupiter. Galileo using only a primitive spyglass saw them first in 1610. They are Jupiter's moons: Io, Europa, Callisto and Ganymede. Finally, the Great Red Spot (GRS)--a cyclone twice as wide as Earth--is also frequently visible. Experienced observers note that larger (10-inch) telescopes and clear steady skies are essential for good views of the GRS.

Although Venus is brighter than Jupiter, it seems less impressive through a telescope. Why? Because Venus is enveloped by thick and utterly featureless clouds. For many years, scientists suspected that Venus's clouds hid a tropical paradise, but now we know, thanks to radar studies and Russian spacecraft that have landed there, that Venus is a hellish wasteland. The surface of Venus is dryer than any desert on Earth and hot enough to melt lead. And those clouds? They are laced with sulfuric acid.

None of that is apparent in the eyepiece of your telescope, though. Venus looks rather pacific and bland. You might note that Venus isn't a complete circle. Like the Moon, Venus has phases, and at the moment it is waxing gibbous, a little more than a half full. More than anything, though, Venus looks like a distant pearl: white, serene, a relaxing sight.

Maybe Steinbeck was right. It is the hour of the pearl, after all.