Next door neighbor Venus, looming in the west, will shine more brightly than anything except the full moon. Mercury will sit below Venus and somewhat to the right, near the horizon -- although the little planet will set within about an hour after sunset.

Mars can be seen at the upper left of Venus, about the width of a fist held at arm's length. It is easy to spot with its distinctive, orange-red glow. Three times farther than Mars to the upper left, is pale yellow Saturn, looking down on the constellation Orion.

Last, giant Jupiter appears as a big, bright star high in the east-southeastern sky.

In a year in which the United States and several other nations have announced plans for new human explorations of the solar system, this rare alignment seems particularly appropriate. "Here we are," the other planets seem to be saying. "Come visit us if you dare."

The celestial parade also provides a coda to more than a year of planetary spectaculars, including several occurring either rarely or for the first time in history.

Jupiter started things rolling early in 2003 when it moved closer to Earth than at any time in the past 250 years -- within 400 million miles. For a little while, its brightness rivaled Venus.

At about the same time, Saturn, the ringed wonder, reached its closest approach to Earth in 30 years -- about 745 million miles. Saturn's rings also reflected the sun's rays perfectly and were tipped toward Earth for the best possible viewing angle. The combination of proximity and ring position had amateur astronomers around the world gasping.

Then, last Aug. 27, Earth and Mars shared what in celestial terms could be considered a head-to-head. The two bodies passed within 34.7 million miles of each other in a phenomenon called opposition -- when Earth reaches a point on a direct line between the sun and one of the other planets.

Although opposition occurs between Mars and Earth about every two years and 50 days, the last one was special. It was the closest proximity of Earth and the red planet in more than 60,000 years. The occasion did not disappoint. Mars appeared five times larger than normal and its brightness increased nearly 60-fold -- enough to reveal new details usually concealed from Earth-based telescopes.

It was as though Mars was drawing closer to receive the next wave of terrestrial visitors. Last December and January, four probes were sent from Earth to the red planet, of which three rendezvoused successfully. Only the little British lander, named Beagle 2 -- in honor of the ship that carried Charles Darwin on his voyage of discovery in the 19th century -- failed to signal its survival.

NASA's Spirit and Opportunity robotic landers have spent the past couple of months analyzing the Martian surface for signs of water. Both have struck paydirt, finding strong evidence the rocks near their respective landing sites were chemically altered by the presence of the liquid.

High above the planet, the European Space Agency's Mars Express orbiter has relayed data revealing the presence of large volumes of water ice at the planet's south pole.

These discoveries mean not only was Mars probably capable of supporting life for a time, it also can do so in the future when the first human expeditions arrive.

Just this past week brought two more new revelations of solar system secrets. Astronomers at the California Institute of Technology confirmed they have observed a new object in our solar system that is much, much farther away than anything ever seen before.

The object has been nicknamed Sedna, for the goddess the Inuit culture believes created all sea life. At present, it is cruising about 8 billion miles from the sun, or nearly three times farther away than Pluto.

Sedna is the first object to be confirmed within a distant zone called the Oort Cloud, the theoretical home of perhaps trillions of comets. Sedna cannot be a comet, however, because it is too large -- somewhere between 800 and 1,100 miles in diameter, or about three-fourths Pluto's size.

Sedna's surface seems to be red, like the planet Mars and Jupiter's volcanic moon, Io. There also is evidence Sedna has a moon of its own.

The lucky aspect of the discovery has to do with Sedna's strange orbit. Despite its extreme distance from the sun, at the moment it is closer -- and therefore more visible -- than it has been during all of recorded history. Sedna is heading back out to a distance that eventually will reach 84 billion miles in a circuit that requires about 10,500 years to complete.

As if to present an opposite of extremes, astronomers detected a small asteroid headed for a close encounter with Earth. The 100-feet-wide body passed within 26,500 miles of us on Thursday afternoon, Eastern time. It is the nearest flyby ever observed.

As long as humans have been able to think and dream, they have looked up into the night sky and wondered about the five star-like bodies that wander the heavens along with the sun and moon -- planet is derived from the Greek word meaning "wanderer."

We have known what they really are for only about 400 years, during the last 40 of which we have sent probes either to or around or past each one of those bodies, as well as some of their satellites.

Now, as we prepare to revisit the moon and perhaps Mars in the next few decades, looking up with our newfound knowledge might provide us with two important reminders: One, our little world is fragile, yet extremely precious in the scheme of things and, two, an enormous universe full of wonder awaits us still.

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