LOS ANGELES (AP) - The five brightest planets visible from Earth have lined up in plain sight, forming a spectacular celestial array that won't be seen again until 2040.

Through the next four weeks, Jupiter, Mars, Mercury, Saturn and Venus will appear tightly clustered in the Western sky. They will be visible in the evening with the naked eye.

"The five naked-eye planets are converging in one part of the sky and from now until mid-May you can see all five at one glance, which is pretty unusual," said John Mosley, an astronomer at the Griffith Observatory in Los Angeles.

Each evening, the alignment will assume different shapes, as the five planets take their orbital paths around the sun. The planets orbit in the same plane, like grooves in a phonograph record, only at different distances from the sun.

Similar bunchings occur every 20 years or so, though they are not always visible. The last they were this visible was in 1940.

In May 2000, the five planets formed a tighter bunch but were so close to the sun that they were washed out by its glare. In 2004, they will appear together again in the night sky, but will be spread over a much wider area, said J. Kelly Beatty, executive editor of Sky & Telescope magazine. They will be as easy to spy at a single glance again until 2040.

"This is the nature of the clockwork of the solar system," Beatty said. "We like to think of it as a way to remind people there is a simple beauty in the heavens that doesn't require any special training to appreciate."

Astronomers stress there is no astronomical significance to the pileup. It is, Beatty said, just a "pretty coincidence."

Doomsayers may likely to see some dark meaning in what astronomers say is purely a celestial coincidence.

In the months before the May 2000 lineup, some thought it foretold widespread catastrophe. In February 1954 B.C., a similar alignment led the Chinese to restart their calendar at year 0, Mosley said.