ROANOKE TIMES
Copyright (c) 1997, Roanoke Times
DATE: Monday, January 27, 1997 TAG: 9701270071
SECTION: NATL/INTL PAGE: A-1 EDITION: METRO
SOURCE: MASON PETERS LANDMARK NEWS SERVICE
Comet-hunting astronomers are like weekend fishermen - everything they catch is big, bigger or biggest, with each new skylight heading our way touted as likely to surpass the one that came before.
So it is with Comet Hale-Bopp, already heralded by some scientists as potentially one of this century's great cosmic displays. Most astronomers agree that the 1997 comet is going to leave a trail of superlatives in the next three months.
Hale-Bopp is whizzing in from the dark and distant reaches of the outer solar system on a regular 4,000-year gravitational trip around the sun, which is 93 million miles from Earth. Hale-Bopp will pass no closer to Earth than about 125 million miles later this spring.
Nevertheless, compared with last year's fuzzy Comet Hyakutake, which put on a pretty good show in the northern sky last March, Hale-Bopp is likely to become a comet to remember, scientists say.
For one thing, Hale-Bopp is big, with an unusually bright head that scientists say is at least 25 miles in diameter. The dirty snowballs that make up the business end of most comets rarely approach this size, astronomers said.
Already Hale-Bopp is showing signs of the kind of activity that make for spectacular celestial displays. It has begun "outgassing," triggered by the warming effect of the sun, while still far out in space. Outgassing is nothing more than a cometary belch, an expulsion of warming gasses from inside the comet's nucleus.
But as belches go, Hale-Bopp is pretty gross. Each burst of gas propels chunks of the comet's icy nucleus into space, where it vaporizes into cometary tail material and other celestial plumage.
Also adding to Hale-Bopp's charms, the comet will be visible at dawn as well as at dusk during much of its passage past the Earth on its way around the sun.
Early February will be a good time to look for Hale-Bopp in the early morning eastern sky.
The comet should rise around 3:30 a.m. local time on Feb. 6, and the moon won't come up for another couple of hours. Don't forget mittens and Long Johns. Comet-watching is chilly business.
Beaches and any elevated spot that reveals a far horizon will provide a good seat for the show. City lights are killers for seeing comets, scientists agree, so try to get away from town.
Check moonrise in your newspaper or almanac and avoid observing the eastern sky near moonrise.
By the end of February, Hale-Bopp will double in brightness. But the moon will be a bother at this time so wait until March when the big show begins.
Each night, the comet will rise a little later and higher until eventually it may be viewed in the darkening sky after sunset. If estimates of some comet-watchers are right, Hale-Bopp should rival Sirius, the brightest star, and the red planet Mars in brightness by March 22.
Also in early March, the comet will be visible in the dawning before sunrise and briefly in the evening after sunset.
By April 1, the comet will reach perihelion - its closest approach to the sun.
By mid-May, Hale-Bopp will have caught up with its destiny to circle the sun and and then rush away into a night that will last 4,000 years before the comet comes back to the smallish star that controls it.
LENGTH: Medium: 66 linesby CNB