[October 2, 1995] -- On July 23, 1995, two amateur astronomers discovered a new comet so big and bright that at 100 million miles beyond Jupiter its glow was equivalent to an 11 magnitude star. Alan Hale in Cloudcroft, New Mexico and Thomas Bopp near Stanfield, Arizona were both using 16-inch reflector telescopes when they saw the glowing mass of ice.
Brian Marsden, a world authority on comets and Director of the Central Bureau for Astronomical Telegrams at Harvard University's Smithsonian Astrophysical Observatory, was surprised.
"It is unheard of for a comet to be visible in small telescopes while so far away. Hale-Bopp could become the comet of the millennium as it comes in towards the sun over the next year or two. It's rare and large. Something this size is the kind of thing that comes to the inner solar system only every century or two."
I asked Prof. Marsden why The London Telegraph newspaper in England used the word "doomsday" in its July 30, 1995 headline: "Doomsday comet surprises astronomers." He answered that when the Telegraph article appeared, "We didn't know too much about the comet's orbit. So there was a remote chance it could hit the earth. But we discovered an Australian photograph taken in April 1993 of what I think is this same comet when it was well over a billion miles from the sun. When I include that position in my orbital calculation, it gives me a period of about 4,500 years, the last time this comet came through our solar system. And this time around, it won't come closer than 10 million miles from earth."
Prof. Marsden said a current estimate of the comet's size is about a hundred miles wide at the icy core with a coma of out-flowing gas stretching a million and a half miles.
"I would say this comet has everything going for it to be the best comet of the century, and maybe of a couple of centuries."
The irony is that Hale-Bopp may very well be the largest comet to come through the solar system for a long time, but when it crosses the earth's plane in May 1997 it will be so far away -- at least 10 million miles from the earth -- that it won't seem very big or bright.
"I would guess that the head of the comet would be about as bright as the star Sirius, the brightest star in the sky. It will be a little fuzzy and should have quite a nice tail spreading out behind it over a large bit of the sky. It might be possible to see it right at the beginning of 1997, or even late 1996. Hale-Bopp will reach its brightest in March and April 1997 before crossing the earth's plane in May."
By March 1997, Hale-Bopp will be visible with the naked eye in the northeastern part of the sky and clearest before dawn. Then in the end of March and into April 1997, the comet will be best in the evening sky just after sunset in the northwest and remain visible for much of the night.
I asked Prof. Marsden about messages on the Internet from anonymous sources saying there have been course corrections in the comet's motion, implying an intelligence behind it.
"Somebody has some crazy idea," he answered, "but I can imagine people are making wild statements like that. They always do. But this is a perfectly clear-cut case of a straightforward comet. The Internet sometimes has a lot of rather weird conclusions people have drawn. I know there are a lot of weird people in England who have been writing to newspapers saying that Halley's comet, which was here in 1986, is coming back soon. I can assure you it has an orbital revolution of 75 years and won't be back before 2061. Hale-Bopp is big, moving more than 10 miles a second, and it would seem to me that even ice vaporization as it moves toward the sun won't have much affect on its orbit."
A year ago in July 1994, comet Shoemaker-Levy 9 broke up into 21 pieces and plunged into Jupiter. I asked Prof. Marsden if Hale-Bopp could break up.
"It could. That would be something. That's one of the unpredictable things. If it were to break up, then pieces from the inside nucleus of the comet would come to the surface. When exposed to solar radiation, that ice would vaporize and the comet would brighten even more."
I also wondered what affect there would be to our planet if Hale-Bopp did break apart.
"No affect," Prof. Marsden said. "The closest the comet will come in one big piece or broken up is at least 10 million miles from earth."
He agreed it's remarkable that both rare comet events should happen so close together in time. By March 1997, those who do see Hale-Bopp will be the first on earth to do so in at least 4,500 years.
Original file name: .CNI - Hale-Bopp.Howe 10.2
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