Maryland, seaboard to get a glimpse of 'unusual' lunar eclipse tomorrow

December 08, 1992|By Douglas Birch | Douglas Birch,Staff Writer

It may resemble some celestial hangover, a lunar eclipse where the moon bears a gray or green complexion and a ragged 5 o'clock shadow.

Beginning at 4:59 p.m. tomorrow, the Earth's shadow will begin to move across the face of the moon as it rises on the eastern horizon. If weather forecasters are right and the skies remain clear around dusk, the total eclipse will be the first visible in Maryland and the rest of the Eastern seaboard since August 1989.

RF In a typical eclipse, the planet casts a crisp, curved shadow that

glows with fiery colors, as some sunlight is snagged in the Earth's envelope of air, bent behind the planet and scattered across the lunar surface.

But thanks to a recent series of volcanic eruptions, the shadow may take on an unusual shape, resembling Mount Fuji, or a headstone, or saw-teeth. And it's likely the shadow, or "umbra," will be darker than normal, appearing mottled gray, glowing green or jet black.

Over the past 18 months, the atmosphere has been bingeing on ash and gases from the eruption of several volcanoes, including Cerro Hudson in Chile, Mount Spurr in Alaska and, most importantly, Mount Pinatubo in the Philippines.

Pinatubo, which shot millions of tons of ash into the stratosphere in June 1991, has produced a cloud of sulfuric acid that has painted pink, azure and scarlet sunsets worldwide. It has blocked enough sunlight to cool the planet by between 1 and 1.5 degrees Fahrenheit.

The debris, astronomers say, could change the shape, color and intensity of the shadow cast by the planet.

Witnesses described the lunar eclipse of Oct. 4, 1884, which occurred 13 months after the massive eruption of Mount Krakatau off the coast of Java, as casting a peaked shadow. The moon was said to glow with a phosphorescent emerald hue, says this month's Sky and Telescope magazine.

A year after the explosive eruption of Tarawera in New Zealand in 1886, the journal Nature reported that a lunar eclipse created a flat-topped shadow resembling a mesa. "[It] was evident the shadow was distorted," a correspondent wrote.

It is not certain that tomorrow's eclipse will have a distorted shadow, or what shape the shadow will take as the event approaches and recedes from "totality," the time when the moon is completely covered in the darkest part of the Earth's shadow. But astronomers are pretty confident the shadow will be darker than normal.

Jim O'Leary, director of the Davis Planetarium at the Maryland Science Center, said that on June 14 a big chunk of the moon seemed to vanish during a partial eclipse, visible in this area through hazy skies.

"Typically in a lunar eclipse you can expect to see a number of different colorations, including coppery red or orange," he said. "But in this particular one, when the moon became eclipsed, it really became very, very dark."

Curtis Roelle, a computer scientist at the Applied Physics

Laboratory and editor of the Westminster Astronomical Society's newsletter, thinks tomorrow's eclipse will be similar.

"With all this volcanic dust up in the air, the chances are the moon will be a dark gray and it will be hard to spot once the totality has begun," he said. "An interesting thing for people to do is to try to judge what color it appears to be. Different people have different impressions, even observing at the same location."

Bob Melrose, a forecaster with the National Weather Service at Baltimore-Washington International Airport, said tomorrow's skies are expected to be clear and cold through the late evening, when the leading edge of a winter storm system is expected to reach this area. "We should be all right" for viewing the eclipse, he said.

The Maryland Science Center in the Inner Harbor will set up telescopes on its front steps for people who want a close-up view of what may be one of the more unusual astronomical events of the year.

The shadow will begin nibbling at the moon's lower left quadrant around 4:59 p.m., completely blocking the moon between about 6:07 p.m. and 7:21 p.m. By 8:29 p.m. the full moon should be visible again.

An eclipse can safely be seen with the naked eye. Using a pair of binoculars or a telescope will help someone pick out details on the moon's surface.

Those interested in watching should grab the chance. The next total lunar eclipse visible in this area will occur in November 1993. By that time, scientists say, most of the sulfuric acid thrown up by Mount Pinatubo will have dissipated.

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