The event is a celestial run-up to a May 5 planetary alignment that has caused some buzz, not so much because it involves six planets, but because some have predicted Earth will suffer calamitous events as a result of a supposed cumulative effect of gravity. Astronomers say there will be absolutely no effect and, in fact, the May alignment won't even be visible because the planets will all be hidden in the glare of the sun.

No special equipment is required to see this week's event.

"It's going to be beautiful," said Vince Huegele, a researcher at NASA's Marshall Space Flight Center. "And best of all, you won't need a telescope to see it, just your naked eye."

At around 8 p.m. local time on Thursday, in the southwest, a thin crescent moon will sit just to the left of the three planets. (See the illustration at the top of this page.) Jupiter will be the brightest of the three planets.

If skies are clear and relatively dark, observers will also be treated to a phenomenon known as earthshine: When the moon is a crescent, the rest of it is illuminated by sunlight reflecting off Earth, hitting the night side of the moon, and bouncing back to Earth.
On April 15, Mars, Jupiter and Saturn will appear even closer to one another, with just 5 degrees of separation. On that night, however, the moon will not join them.