Last modified: Tuesday, April 30, 2002
Five bright planets dance in the evening
The five planets visible with the unaided eye have assembled in the western sky, presenting a rare opportunity to see all of them at once simply by looking westward as soon as the sky has darkened, about 45 minutes after sunset. The only requirement is a clear view of the west-northwestern sky, since some of the planets are very low.
This is the best gathering in nearly two decades for Mercury, Venus, Mars, Jupiter and Saturn. During May, viewers can see a different arrangement each night as the planets converge and then move among each other like stately dancers.
The main event will be May 4-7, when Venus, Saturn and Mars will form a tiny triangle low in the west after sunset. For viewers in the United States, they will be closest on May 6. All three will fit into the field of view of binoculars, with dazzling white Venus being especially impressive when viewed in this manner. Bright yellow Saturn and pale orange Mars will complete the trio. Mercury will be slightly to the lower right (north) of this triangle, and the bright orange star Aldebaran will be about the same distance below the triangle. The appearance of four bright planets and a bright star so close together is an extremely unusual event.
Jupiter will be considerably higher than the other planets early in May, second only to Venus in brightness and easy to spot to the upper left (south) of the triangle. Jupiter will be accompanied by the bright stars Castor and Pollux of the constellation Gemini the Twins.
On May 13, these five planets will have their minimal separation from one end of the line to the other. From highest to lowest, the order will be Jupiter, Venus, Mars, Saturn and Mercury, with the crescent moon added at the bottom as an extra treat. Mercury will be hard to locate by then, but the other four planets will still be clearly visible.
In the first week of May, use bright Venus as a guide to Mercury by searching below and to the right (north) of Venus about a half hour after sunset. Binoculars will help pick the little planet out of the twilight glow, but even in cities Mercury will be bright enough to see without optical aid as the sky darkens. Mercury will begin falling back toward the horizon after May 4, eventually disappearing into the solar glare as it passes between Earth and the sun.
During the last two weeks of the month, first Saturn and then Mars also will drop away from Venus into the twilight. But Jupiter will come down to meet Venus at month's end in a dramatic encounter between the two brightest planets, providing an appropriate conclusion to an extraordinary month.
Viewing information and graphics displaying the different combinations of planets that will form are available at http://www.space.com/spacewatch/. Images are available for republication by the media at http://www.space.com/spacewatch/press_planet_images.html.
Comet Ikeya-Zhang (pronounced ee-KAY-uh JONG) will fade during May, becoming visible only in binoculars and telescopes. This bright comet was discovered on Feb. 1 and named for the two skywatchers who first spotted it. After it passed closest to the sun on March 18, it came nearest to Earth on April 29. For details about the discovery and appearance of Comet Ikeya-Zhang, see http://SkyandTelescope.com/observing/objects/comets/.
This month, Earth will plow through dust left behind in space by Comet Halley, causing the Eta Aquarid meteor shower that will peak before dawn on May 5 or 6. Meteors will be visible both nights and for a couple of nights before and after those dates as well. The last-quarter moon will interfere somewhat, but the brightest meteors will still be easy to see. Many of the Aquarids skim through the top of the atmosphere, producing long paths high overhead. They will appear to come from a point in the constellation Aquarius, which will rise in the east about two hours before the sun, limiting the best viewing to those two hours.
The bright white star Vega in the constellation Lyra the Harp is part of a trio of conspicuous white stars called the Summer Triangle that crosses the sky every night during the warm months in the Northern Hemisphere. Vega is the first of them to rise in the east each night. The others are Altair in the constellation Aquila the Eagle to the south and Deneb in the constellation Cygnus the Swan to the north. When you are looking at Deneb and Altair, you are also looking at the Milky Way, though it is obscured by city lights.
In an unusual occurrence, the moon will pass in front of (occult) three bright planets on May 14. However, each occultation will be visible only to viewers in certain locations on the globe. In this interesting event, a bright star or planet disappears behind the moon and then pops out again a few minutes later. Saturn will be blocked for observers in parts of the United Kingdom, Scandinavia and the Arctic region; Mars will be the moon's target for part of South America; and Venus will be covered for those watching in an area of the South Pacific. Information about where and when to watch is available at http://www.lunar-occultations.com/iota/planets2002/planets2002.htm.
The moon will be at last quarter on May 4, new on May 12, at first quarter on May 19 and full on May 26.