Stargazers will get a rare triple planetary treat this weekend with Jupiter, Mercury and Mars appearing to nestle together in the predawn skies.
About 45 minutes before dawn on Sunday, those three planets can be obscured from view by the average person's thumb.
They will appear to be almost as close together on Saturday and Monday, but Sunday they will be within one degree of each other. Three planets haven't been that close since 1925, said Jack Horkheimer, executive director of the Miami Space Transit Planetarium.
And it won't happen again until 2053, he said.
"Jupiter will be very bright and it will look like it has two bright lights next to it, and they won't twinkle because they're planets," said Horkheimer, host of the television show "Star Gazer." "This is the kind of an event that turns young children into Carl Sagans."
The planets are actually hundreds of millions of miles apart, but the way the planets orbit the sun will make it appear that they are neighbors in the east-southeastern sky. They'll be visible in most parts of the world -- in the Western Hemisphere, as far south as Buenos Aires and as far north as Juneau, Alaska, Horkheimer said.
The experts differ on just how to look at the planets. Horkheimer said naked-eye viewing was fine, but binoculars or a telescope were better.
But if you are going to use a telescope, be careful: The planets are so close to where the sun will soon rise that if you linger, you might gaze at the sun through the telescope and damage your eyesight, said Michelle Nichols, master educator at Chicago's Adler Planetarium.
Ed Krupp, director of the Griffith Observatory, said that it would be hard to see the event "with an unaided eye, particularly in an area that is highly urbanized."
The way to find the planets, which will be low on the east-southeast horizon, is to hold your arm straight out, with your hand in a fist and the pinkie at the bottom. Halfway up your fist is how high the planets will appear above the horizon, Nichols said. Jupiter will be white, Mercury pinkish and Mars butterscotch-colored.
"It is a lovely demonstration of the celestial ballet that goes on around us, day after day, year after year, millennium after millennium," said Horkheimer. "When I look at something like this, I realize that all the powers on Earth, all the emperors, all the money, cannot change it one iota. We are observers, but the wonderful part of that is that we are the only species on this planet that can observe it and understand it."
On the Net:
Where to look for the three planets: http://www.siennasoft.com/stargazer/1513.shtml