The planetarium is not hosting any programs to watch the planets, but amateur stargazers should be able to see much of the array from their backyards, Martin said.
Because of the planets' varied orbits, it could be more than 100 years before they are so close together and in a similar pattern. While a similar display is expected to take place in May 2000, astronomers have pointed out that some of the planets will be too close to the sun to be seen from earth.
In the current grouping of planets, Mercury is the rarest find because it is so close to the sun and usually difficult to see, Martin said. Legend has it that Copernicus, the founder of modern astronomy, never saw Mercury, he said.
"You very seldom see it in the glare," Martin said.
Tonight, Mercury will be just above the southwestern horizon, beneath the moon and to its north. Closer to the moon will be an orangy Mars and then a radiant Venus, the brightest object in the sky.
Continuing south and higher on the horizon will be Neptune and Uranus, both of which will require binoculars for viewing.
Farther south will be Jupiter and, in the southeastern sky, Saturn. Although both can be seen with the naked eye, a telescope will be needed to view Saturn's rings and binoculars will be needed to see the four Jupiter moons that are visible, Martin said.
"This is a real good time to see these things," he said.
Pluto, to the north of Mercury in the low southwestern sky, will be visible only with a high-powered telescope, Martin said. Even then it can be distinguished from stars only by its movement, he said.