For astronomy buffs, here's a guide to assorted celestial events and astronomical phenomena in 1989.
Some extraordinary sights are in store this year for those who turn their eyes to the cosmos. A lengthy total lunar eclipse, dazzling meteor showers and displays of northern lights, and several spectacular conjunctions — or close pairings — of planets and other celestial objects are just a few of the celestial events ahead. And for a bonus, even though we won't be able to actually see it, Voyager 2's final and closest flyby of a planet — Neptune — promises exciting photographic revelations.
On the afternoon of March 7, the first of two partial solar eclipses (the only solar eclipses this year) will be visible from most of the western half of the U.S., but only viewers in Alaska and Hawaii will get to see the whole show, during which 83% of the sun's diameter will be hidden. The second partial eclipse of the sun, on August 31, will be even less accessible—it'll be observable only from southern Africa, Madagascar and the Antarctic. It will also be the last truly partial eclipse of the sun for more than three years.
The two total lunar eclipses of 1989 hold more promise, although the first, on February 20, will be visible in the Western Hemisphere only from northwest North America, and only as it begins, just before dawn. The year's potentially spectacular second total lunar eclipse, however, should more than make up for its daylight-obscured predecessor. It'll be visible everywhere in the Western Hemisphere except northwest North America, and will reach totality during full darkness—on the night of August 16. Weather permitting, it'll be the first really proper view that people in the eastern U.S. have had of this kind of event since 1982. The August eclipse will also be, by far, the longest total lunar eclipse visible anywhere in the world since 1982: It'll last 96 minutes, only about 11 minutes short of the maximum possible.
The drama will open with the moon entering Earth's not-very-dark peripheral shadow, the penumbra, at 8:23 P.M. EDT. The penumbral shading probably won't be noticeable until close to 9 P.M. Then, at 9:21 P.M., the real excitement will begin when Earth's dark central shadow, the umbra, first touches the left edge of the moon. The umbra will creep slowly across the lunar surface until, at 10:20 P.M., the moon will be completely covered, initiating the "total" stage.
In a total eclipse, the moon's glow usually is reduced to about 1/10,000th of normal fullmoon brightness, but some sunlight does filter through Earth's atmosphere to reach the moon's surface. So don't expect Earth's satellite to be blacked out entirely. Even at mid-eclipse (at 11:08 P.M.), when the moon will be just below the center of Earth's umbra, the moon will not disappear nor will it even appear gray. The exact shading depends on the types and amount of atmospheric dust present around our planet at the time. Reddish orange is most likely, although some total lunars are indeed black and others bright orange. Each is different, so be sure to see this one. You won't get another look at a total lunar eclipse until 1992!
The eclipse will pass totality at 11:56 P.M. The last edge of the umbra will slide off the moon at 12:56 A.M. EDT, and then the penumbra will slip away at 1:53 A.M.
Astronomers were amazed last year by a tremendous increase in solar activity. Among other developments, there were several cases of naked-eye sunspot groups, including one of the largest ever observed (early last July). Solar activity, which includes flares and sunspots, usually builds to a maximum about once every 11 years. Astronomers weren't expecting the next peak until 1990 or later, but now it seems certain that the maximum will occur in 1989, and that it will be among the strongest peri ods of solar activity in recorded history. As one result, 1989 also promises to be a prime year to watch the north sky late at night—especially when large sunspot groups have just passed the sun's central meridian—in hopes of seeing the northern lights, or aurora borealis. Locations above 40° north latitude are best for viewing the phenomenon, but when great auroral storms occur, even folks in Florida and Texas can see these majestic, shifting patterns of often colorful light.
Meteors are the shooting stars or falling stars we see when random bits of rock and iron from outer space enter our atmosphere at such high speeds that they burn up from friction with air molecules. Meteor showers, on the other hand, are predictable on an annual basis. They occur when increased numbers of meteors streak from certain points in the heavens on certain nights each year. These are the nights when our planet passes through concentrations of meteoric material — comet debris, actually — that exist at specific places along Earth's orbit. Meteor observers can see fireballs (meteors even brighter than Venus), bolides (exploding meteors), meteor trains (the lingering trails of some meteors), and "ordinary" meteors of all colors. To see the maximum number of meteors in a shower, choose a place well away from city lights and hope for clear, moonless skies.
This year, moonlight will ruin views of four of the six major showers that were visible last year: namely, April's Lyrids October's Orionids, mid-November's Leonids and mid-December's Geminids. To compensate, though, you'll get a look at several showers that weren't visible in 1988, plus repeat performances of the Taurids and Perseids.
Look for as many as a dozen Quadrantid meteors an hour coming from the northeast in the last few hours before dawn on January 4. The Eta Aquarid meteors—debris from Halley's comet—will fly out of the southeast at rates of 10 or more per hour just before morning twilight on May 3 and 4. The Delta Aquarids are best after midnight on evenings at the very end of July and, the start of August. They and their lesser companions, the Capricornids, are often golden, and come from the south in numbers as great as several dozen per hour.
The best time for viewing the often spectacular Perseids shower will be after late moonsets in the predawn hours of August 12 and 13. On those mornings, the swift meteors may rain out of the heavens at a rate of up to one a minute. Try not to miss them! Also, the year's last major visible shower, the Taurids, should yield five or more slow, bright meteors an hour out of the southeast during the first week of November.
For easy reference consult our compilation of Sky Events for 1989.