ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Thursday, March 21, 1996 TAG: 9603210034
SECTION: NATIONAL/INTERNATIONAL PAGE: A1 EDITION: METRO
SOURCE: MATT CRENSON DALLAS MORNING NEWS
note: above
HEAD FOR THE HILLS - or any other dark place - this weekend to catch a glimpse of Comet Hyakutake. Astronomers say it may be the brightest in 20 years.
With each passing day, the potential astronomical spectacle of the decade gets 3 million miles closer to Earth.
Just two months ago, astronomers didn't even know about it. But now they're giving good odds that Comet Hyakutake will be the most impressive comet since 1976.
``It certainly looks like a winner,'' said Hal Weaver, who studies comets at the Applied Research Corp. in Landover, Md.
In fact, some astronomers predict that Hyakutake could be the most visible comet since the invention of the telescope 400 years ago. Because the comet will pass within an astronomical hair's breadth of Earth - missing the planet by a mere 10 million miles - astronomers expect it to appear at least as bright as the most prominent stars.
``From everything I hear on the grapevine, this is going to be a huge event,'' said Randy Peters of the Fort Worth Museum of Science and History's Noble Planetarium.
Today the comet is barely visible just before dawn in the southwestern sky. By Monday, when Hyakutake is at its closest to Earth, it should be much more impressive. It will appear next to the Big Dipper ``like a cotton ball with a concentration near its center,'' Weaver said.
Amateur astronomer and comet hunter Yuji Hyakutake of Kagoshima, Japan, discovered the comet Jan. 30, using a giant pair of binoculars with lenses 6 inches across. Within a few weeks, the comet has hurtled to the top of the astronomical agenda.
The Hubble Space Telescope will take a look on Monday and will follow the comet well into April. Ground-based telescopes will be watching as well, in a worldwide attempt to determine the comet's composition and structure.
``This is an excellent candidate for scientific observation,'' Weaver said.
Comet Hyakutake is expected to be visible to the naked eye until mid-April. After passing Earth next week, the comet will go near the sun and then swing back out toward the place whence it came - the outermost suburbs of the solar system.
Unlike a meteor, or shooting star, the comet will be a steady object in the sky - even though it will be moving 126,000 mph. Over the course of a few weeks it will gradually move across the heavens, passing from the constellation Bootes toward the Little Dipper, then just to the right of the North Star and the constellation Cassiopeia.
Besides keeping fascinated observers up past bedtime, the comet isn't expected to disturb life on Earth. Recent tabloid predictions of impending doom are simply wrong. The comet's chances of hitting Earth are zero.
Comets become more visible as they approach the sun because their primary constituent - ice - turns to vapor when heated. That causes the comets to disintegrate, releasing highly reflective dust that surrounds the object like a halo.
The more dust a comet throws off as it hurtles through space, and the closer it is, the more impressive it appears.
Halley's comet, which last passed through the inner solar system in 1986, wasn't very impressive because it never got closer than 39 million miles. The last really good one was Comet West, which didn't get very close to Earth. But when it passed in March 1976 the comet broke apart, releasing a big puff of dust that made it much more visible.
Comet Hyakutake should be a good show because it has a combination of those two qualities, astronomers said. The comet will be the most active to pass Earth in the last 400 years, and the fifth-nearest approach of this century, Weaver said.
In fact, the comet will come so close that it won't look like most comets, he said. The typical comet is a point of light with a tail. Comet Hyakutake will look more like a fuzzy spot in the sky.
Donald Yeomans of NASA's Jet Propulsion Laboratory in Pasadena, Calif., warned against hyping the comet too much.
To someone familiar with the night sky it should be an impressive sight, he said. But for those who can't find the North Star without first figuring out where north is, it probably won't seem like a big deal.
``Most people today are used to fireworks and big light shows,'' Yeomans said. ``They're not used to seeing anything very subtle.''
LENGTH: Medium: 84 linesby CNB