LOS ANGELES - Five planets, the sun and the crescent moon are grouping together in the sky for what would be a rare celestial spectacle if it were not completely obscured by the sun's glare.
Astronomers say Friday's planetary pileup will mark the tightest alignment of Mercury, Venus, Mars, Jupiter, Saturn and the moon since 1962. On May 17, the still-sunblocked planets will cluster even closer, though the moon will have moved away by then.
Star gazers must wait two more years before another such grouping takes place, said John Mosley, an astronomer at Griffith Observatory.
''May 2002 will involve all five planets plus the moon,'' he said. ''It will be similar to the one happening now, except you'll be able to see it.''
The alignment has been in the works for over a month. In early April, Mars, Jupiter and Saturn were close together in the evening sky and outside the sun's glare. Now, all five planets visible to the naked eye are on the opposite side of the sun from Earth.
Planetary alignments occur when three or more celestial objects move into positions so that a straight line could be drawn through their centers. But the definition is a bit loose: Planets that appear close together in the sky are considered aligned.
For centuries, doomsayers have predicted the end of the world whenever an unusual alignment occurs. But astronomers say the planet has never reacted to such an event.
One book, ominously titled ''5/5/2000: Ice, The Ultimate Disaster,'' predicts the alignment and increased solar activity will trigger a chain of events that will cause the Earth's crust to slide and the poles to shift.
''It would be a geological Armageddon,'' author Richard Noone said last month. ''You'd have volcanism going on globally. Earthquakes beyond the scale anything Richter ever dreamed of. Tsunamis hundreds of feet high, sweeping hundreds of miles inland.''
Mosley dismisses the prediction and has included a quote from Noone's book to open a debunking planetarium show titled ''Cosmic Catastrophe.''
''If this were true, it would have happened already,'' he said.
Noone, who moved his family to safety in Georgia, did not return a telephone message Thursday, but in a news release seemed to be backing away from the claim that a pole shift was imminent.
''Careful modeling would be necessary to predict how often in the past this has occurred and what the likelihood of it happening soon might be,'' he said. ''Unfortunately, we don't understand enough about the various independent and interrelated influences which might be involved to make any such meaningful predictions.''
On the Net: Griffith Observatory: http://www.griffithobs.org
Noone's Web site: http://www.552000thebook.com/