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Comet Hale-Bopp Update

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COMET HALE-BOPP UPDATE

Sky & Telescope News Bulletin
May 30, 1997

RETURN OF THE MINI-COMETS

Based on newly released images, Earth is being pelted more or less continuously by small comet-like objects. A camera on the orbiting spacecraft called Polar recorded the intruders has they sliced through Earth's uppermost atmosphere. The interlopers are thought to weigh 20 to 40 tons and consist of almost pure ice. They begin to break up at altitudes at least 10,000 km above Earth, so they never reach Earth's surface. Their water creates neutralized "holes" in the ionosphere that are seen by Polar's cameras. The comets strike at rates of five to 30 *per minute.* If this rate has been steady over billions of years, they have contributed much of Earth's water and perhaps a large proportion of its organic constituents.

Physicist Louis Frank (Univ. of Iowa) first called attention to these mini-comets in 1986, based on their appearance in other spacecraft data. But his idea was widely criticized at the time because there was no other observational evidence for the comets' existence.

BOTTOM'S UP FOR HALE-BOPP

Observers in the Southern Hemisphere are finally getting to enjoy Comet Hale-Bopp. The comet is still near magnitude 2, but the views from down under are a weak imitation of what Northerners were treated to earlier this year. The comet is some 22 deg from the Sun, so it can only be seen well up while still in twilight, and its magnificent dust tail has shrunk to just a couple degrees in length. In fact, when S&T Contributing Editor Steve O'Meara saw it from Hawaii last week, no tail was visible with his unaided eyes. "In binoculars," he reports, "there was just a dinky fan of dust and a stubby jet of ion tail." He adds that the coma has become more diffuse.


Copyright 1997 Sky Publishing Corporation. S&T's Weekly News Bulletin is provided as a service to the astronomical community by the editors of SKY & TELESCOPE magazine. Widespread electronic distribution is encouraged as long as this paragraph is included. But the text of the bulletin and calendar may not be published in any other form without permission from Sky Publishing (contact permissions@skypub.com). S&T's Weekly News Bulletin and "Sky at a Glance" are available via SKY Online on the World Wide Web (http://www.skypub.com/). At present they are not available via electronic mailing list. comethome.gif Comet Hale-Bopp Home Page

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