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Hal Kibbey
OCM
hkibbey@indiana.edu
812-855-0074

Last modified: Wednesday, April 3, 2002

STAR TRAK

Five bright planets cluster in April

April will present a rare opportunity for even casual observers to easily see several bright planets in the western sky after sunset.

This will be the best gathering in nearly two decades for the five planets visible with the unaided eye: Mercury, Venus, Mars, Jupiter and Saturn. The tightest grouping and the best pairings and clusters will happen in May and early June, but during April, viewers can watch each night as the planets assemble.

Every April evening at dusk, Jupiter, Saturn, Mars and Venus will be visible in that order from upper left (south) to lower right (west). Mercury will appear at the bottom of the line near the west-northwestern horizon during the second half of the month. Jupiter will be very high in the west at the upper end of the line.

Yellow Saturn will be accompanied by the bright orange star Aldebaran to its lower left (south). To the right (north) of Mars will be the Pleiades star cluster. Brilliant white Venus will be by far the brightest of the group, and orange Mars will be the faintest.

Anyone with a clear view of the western sky will be able to see these planets as they converge, without special equipment. Viewing information and graphics displaying the different combinations 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

After sunset on April 4 in the Northern Hemisphere, Comet Ikeya-Zhang (pronounced ee-KAY-uh JONG) will be low in the northwest near the famous Andromeda Galaxy. This bright comet was discovered on Feb. 1 and named for the two skywatchers who first spotted it. Both the comet and the galaxy will be visible to the unaided eye in a clear dark sky far from city lights. For those watching from urban areas, binoculars or a small telescope will show both of these objects in the same field of view.

Though it passed closest to the sun on March 18, the comet has remained steady in brightness for two weeks. It will be nearest to Earth on April 29, remaining visible to observers in the Northern Hemisphere throughout the month. In late April it will be near Polaris, the North Star, and will be above the horizon all night for most of the United States and all of Canada and Europe.

Calculations indicate that this is the comet seen in 1661, which is making its first return visit to the inner solar system in 341 years. No other comet with such a long period has been seen on successive orbits around the sun. Halley's Comet, for example, passes our way every 76 years or so.

For details about the discovery and appearance of Comet Ikeya-Zhang, see http://SkyandTelescope.com/observing/objects/comets/.

Meteor shower

The Lyrid meteor shower will peak on the night of April 22-23, with 15 to 20 meteors per hour normally visible in a clear dark sky. But this year the first-quarter moon may wash out the fainter meteors. The meteors can appear anywhere in the sky, but they will seem to come from a point (called the radiant) in the constellation Lyra the Harp, which gives the shower its name. The bright white star Vega will be almost at the radiant, and the meteor count should be highest when Vega is well above the eastern horizon, beginning around 11 p.m. local time in the Northern Hemisphere and lasting until the start of morning twilight.

Vega is part of a trio of conspicuous bright white stars called the Summer Triangle, and Vega is the first of them to rise 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 usually obscured by city lights.

Lunar occultation

The moon will pass in front of (occult) Saturn on April 16 for viewers in parts of the northwestern United States, Alaska, northern Canada, Greenland, northern Europe and Scandinavia. In this interesting event, a bright star or planet disappears behind the moon and then pops out again a few minutes later. Information about where and when to watch is available at http://www.lunar-occultations.com/iota/planets2002/planets2002.htm.

Moon phases

The moon will be at last quarter on April 4, new on April 12, at first quarter on April 20 and full on April 26.