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The Hale-Bopp comet has become somewhat of a phenomenon. Jeffrey Kaye of KCET-Los Angeles reports.

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Correspondent's note: for a closer look at the comet, visit Dr. Bob Yen's Hale-Bopp Web site.

JIM LEHRER: Now, a look into the sky at that Hale-Bopp Comet. Jeffrey Kaye of KCET-Los Angeles reports.

JEFFREY KAYE: For the second straight year stargazers have been treated to a bright comet sailing by the Earth. Last spring it was comet Hayukatake. Now it's an even brighter passer-by, Hale-Bopp. Sunday night visitors came to the Griffith Observatory in Los Angeles hoping to see a celestial double-hit, a lunar eclipse as well as the comet.

JOHN MOSELY, Astronomer: Comet Hale-Bopp is in the sky right now as we speak over the Hollywood sign up in that large gray cloud.

JEFFREY KAYE: Although the cloud obscured the actual comet, visitors could learn how to cook up their own miniature version in a presentation by astronomer John Mosely.

JOHN MOSELY: The main ingredient in a comet is ice, different kinds of ice.

JEFFREY KAYE: Mosely mixed common ingredients, water, ice, dry ice, which is solid carbon dioxide, water, sand, and dust, and a charcoal briquette.

JOHN MOSELY: When we photographed the nucleus of Halley's Comet up close in 1986, we found, to our surprise, it was as black as this charcoal briquette. There's a small amount of carbon material. So here is a ground up charcoal briquette which we'll add to our mixture. By the way, the way real comets were made is they formed in the outer part of the solar system at the same time the rest of the planets and the sun were forming, but they formed in the outer part where there's a lot of ice. And they're visitors from afar to our neighborhood. Now, this is going to be a little smaller than Hale-Bopp. The nucleus of Hale-Bopp is 20 miles across. And there we go, a comet nucleus. (applause)

JEFFREY KAYE: And like a real comet nucleus, this model has cracks in its crust. Gas jets out from the comet's cracks to form Hale-Bopp's split tails which are being photographed around the world. At the Jet Propulsion Lab in Pasadena Ron Baalke has collected nearly 2,000 Hale-Bopp photographs which he makes available on the Internet. As the photographs show, as the comets travel through space, they rotate and shoot out their jets of dust and gas.

RON BAALKE, Jet Propulsion Lab: And that causes this ripple effect that we're seeing here. Now the interesting thing on this, just by looking at the--each of these hoods--these ripples, they've been able to determine the rotation rate of the comet, so it rotates. The current value is 11.4 hours. That's how long it takes for a comet to do a full rotation. The white tail is the dust tail. Another one is a gas tail. That's always the one that has a little color to it.

JEFFREY KAYE: Astronomer John Mosely says the dust tail is typically much brighter than the gas tail.

JOHN MOSELY: And the gas tail fluoresces by sunlight lighting it up and causing the gas to glow like it does inside a fluorescent light. Dust tails are caused by dust that is released when the gas evaporates. Dust shines by reflected sunlight, and dust tails are very bright. When we look at Comet Hale-Bopp, we're seeing largely the dust tail. And that's what you see if you're in a bright urban area. The gas tail is much thinner and longer but more difficult to see from a brightly lit environment.

JEFFREY KAYE: The Hale-Bopp comet has become somewhat of a phenomenon. Stores say telescope sales have increased. "NewsWeek" Magazine put it on its cover. Observatories are selling T-shirts, and the men who discovered it in July 1995, Alan Hale of New Mexico and Thomas Bopp of Arizona, have become astronomical celebrities.

SPOKESPERSON: You've got an eclipse of the moon going on. We've got the comet in the sky.

JEFFREY KAYE: Even though Hale-Bopp was blocked by clouds Sunday night in Los Angeles, there were periodic glimpses of the lunar eclipse. And the good news is that Hale-Bopp should be visible for several more weeks.

JOHN MOSELY: To see the comet face Northwest as soon as the sky is growing dark. The comet will be one of the first stars to appear as the stars are appearing. Look in the Northwest fairly low, and the comet then sets a couple of hours after sunset.

JEFFREY KAYE: Until when?

JOHN MOSELY: The comet will be bright through April and into May. It will be at its best the first week of April. That will be the first time to see it. But it should remain bright through the month, and people will be watching it into May.

JEFFREY KAYE: After May you're out of luck. Comet Hale-Bopp won't pass this way again for another 2400 years.

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