ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Sunday, October 27, 1996 TAG: 9610280165
SECTION: NATIONAL/INTERNATIONAL PAGE: A-14 EDITION: METRO
DATELINE: TUCSON, ARIZ.
LARGER than Hyakutake, the year's first spectacular comet, Hale-Bopp will pass closest to Earth on April 1.
Viewed through powerful telescopes, comet Hale-Bopp is already putting on a spectacular light display - and astronomers say the best is still six months away.
``I'm looking forward to a fantastic show in mid-spring,'' said Harold Weaver, an astronomer who has been following the progress of Hale-Bopp through the Hubble Space Telescope.
Weaver said the comet is erupting with bursts of gas every 18 to 26 days as water is boiled away from its icy core.
``It would look like a sprinkler if you could see it from above,'' Weaver said at the national meeting last week of the planetary division of the American Astronomical Society.
Astronomers have been observing Hale-Bopp for more than a year, and many observatories are gearing for a major study of the speeding space traveler.
Discovered in July 1995 by amateur astronomers Alan Hale of Cloudcroft, N.M., and Thomas Bopp of Stanfield, Ariz., the streaking ball of ice and dust is the second major comet to pass near Earth in what astronomers have come to call ``a year of the comet.''
Last May, the world's telescopes focused on comet Hyakutake. It was the brightest comet viewed from Earth since the appearance in 1976 of Comet West.
Weaver said that Hale-Bopp is considerably bigger than Hyakutake and may erupt with 30 times more gas and dust. But Hale-Bopp, in its nearest pass of the Earth on April 1, will be more than 100 million miles farther away, somewhat diminishing its light show.
Hale-Bopp appears to be about 18 to 25 miles across, about four times bigger than Hyakutake, and the new comet is much more energetic in the release of gas.
``This comet is considerably bigger than Haley's, which is considered to be a large comet,'' Weaver said.
Astronomers observe comets in different spectrums to measure their chemical content. Gases spewing from the comet and then lighted by the sun contain chemicals that have specific light signatures.
For taking such data, said Weaver, ``Hale-Bopp will be the most productive comet we have ever measured.''
Hale-Bopp is expected to be visible just after sunset in the Western sky starting on April Fools' Day. It will dip behind the sun after a few days and not be visible again until August. When it returns to view, however, it will be more than 200 million miles from Earth and much fainter.
Mike A'Hearn, a University of Maryland astronomer, said that Hyakutake has ``opened up a whole new field of study'' because astronomers discovered the comet was producing X-rays.
X-rays had never before been measured from a comet, but once that radiation was found with Hyakutake, astronomers re-examined data from earlier comets. A'Hearn said that X-rays were found to have been produced from five earlier comets.
Astronomers are still uncertain exactly how the comet produces X-rays, but A'Hearn said it may be from the collision of clouds of dust erupting from the comet and the solar wind, the steady stream of radiation from the sun.
A'Hearn said that early studies of Hale-Bopp suggest that the comet is not a stranger to the neighborhood of the Earth.
``We know the comet has been through the inner solar system hundreds of times,'' A'Hearn said.
LENGTH: Medium: 68 linesby CNB