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Halley's Comet is coming.

HALLEY'S COMET IS COMING

Halley's Comet is back, and once again the human race is starting to skitter around like a drop of water on a hot griddle.

Entrepreneurs are popping out of the ground and spieling as they come. Already 16 different Halley's T-shirts are being sold. An adman named Owen Ryan has founded a General Comet Industries. At least a dozen new comet books will come out this year and next, not to mention comet cocktails, comet stamps, comet medals, hats, posters, gag pills, stock certificates and bumper stickers ("Halley's Comet Watchers Do It Every 75 Years').

Waiting in a New Jersey warehouse are stocks of "Halleyscopes,' relatively simple refractors retailing for about $200 and "especially designed for first-time telescope users.' Cruise lines are booking passages for trips to South America, Australia and other points in the Southern Hemisphere, where the comet will be brightest. Somebody is campaigning to get American cities to turn out their lights after midnight so people can see the thing better.

And Halley's is still on the far side of Jupiter, almost a billion miles away, a dirty, 6-billion-ton snowball three miles wide, idling along at 20,000 miles an hour.

The 200-inch Palomar Observatory telescope claims the first sighting during the current visit--October 15, 1982--of what was then a speck of light in Canis Minor. But by late November 1985, shortly after it begins its eight-month rush around the sun at 140,000 mph, it should be visible to anyone who looks hard enough in the right place at the right time.

By then the front end, the coma, blossoming brightly in the sun as it sublimates from solid to gas, will be 100,000 miles in diameter. It will be followed by a tail 50 million miles long and a history that goes back 3,000 years.

Who Saw It First?

The conventional best bet for the first sighting of Halley's (pronounced as in "alleys') seems to be a Chinese report of 240 B.C., making this visit the 29th recorded appearance--though many stargazers are happier with a Han dynasty record, "a comet appears in the east,' in the fall of 87 B.C.

In any case, the comet has had plenty of publicity over the years. It is woven into the Bayeux tapestry because it appeared in 1066, the year of the Norman Conquest. It shines above a Giotto Nativity fresco disguised as the Star of Bethlehem and painted after Giotto saw it in 1301. (Was it indeed the Star of Bethlehem? Probably not, because its nearest relevant appearance was in 12 B.C., just outside the period in which Jesus' birth has been bracketed.)

The visit of 1456, surely seen by a couple of European kids named Christopher Columbus and Leonardo da Vinci, was described by Leonardo's tutor: "Its head was round and as large as the eye of an ox, and from it issued a tail fan-shaped like that of a peacock. Its tail was prodigious, for it trailed through a third of the firmament.'

It worried people. The very word "disaster' means "evil star,' as Nigel Calder points out in his most entertaining and useful book, The Comet Is Coming! Time and again, the experts predicted famines, wars and plagues. Queen Elizabeth's people tried to keep her from even looking at the comet of 1577, but she marched straight to the window and fixed it with her cold gray eye. Nothing happened, either to her or to the comet.

In the Dark Ages comets were thought to be the work of the devil, and some insisted they could actually smell a sulfurous odor in the night skies ("Halleytosis,' says Calder). The 1664 comet inspired this dreadful prediction from one Englishman: "These Blazeing Starrs! Threaten the World with Famine, Plague & Warrs, to Princes, Death; to Kingdoms, many Crofses; to all Eftates, inevitable Loffes! to Herdsmen, Rot; to Plowmen, haples Seafons, To Saylors, Storms; to Cittyes, Civill Treafons.' The following year, bubonic plague struck down a fifth of London's population.

Old-time fears seem quaint to us. But in 1910, when it was learned the Earth would pass through Halley's tail, many people were panicked by the announcement that comet tails could contain poisonous cyanogen gas. Some citizens went around in surgical masks. Some took comet pills that serendipitously appeared on the market.

Edmond Halley got excited about comets in 1682, when a spectacular one blazed over Britain. He had already devoted some thought to the subject and concluded that they may well have caused Noah's Flood. The comet of that year became Isaac Newton's experimental proof of his theory of gravity, and the notion that a comet might be riding an extremely elongated, gravity-controlled orbit rather than a straight line made Halley famous.

Because they seem to fly in a straight line, comets had puzzled observers for centuries. Besides, Aristotle had encouraged generations to assume that comets were very close, like rainbows.

Halley was the first to work out the comet's correct path on a 76-year orbit and identify it as the same one that had passed through in 1531 and 1607. To dramatize his achievement, he told the world it would return in early 1759.

It did. Unfortunately for Halley, he was by then 16 years in his grave.

How to See Halley's Comet

Scientists, perhaps burned a little by the Kohoutek fiasco of 1973-74, have been warning that Halley's won't be as flamboyant this time as in 1910--it will go behind the sun rather than in front of it.

But now comes word that the core is vaporizing into a coma much sooner than expected, making it up to 100 times brighter than it was supposed to be at this point. It will shine its brightest in February 1986, when it closes on the sun. By March and April, the best viewing period, the tail should be 25 degrees, or 50 moon diameters long.

From the eastern seaboard one should look low to the southeast in the predawn sky, and to the sunset area in the late evening. "The lightness can vary,' says David De Vorkin of the Smithsonian--where, as you might expect, a planetarium show called "Comet Quest' has opened at the Air and Space Museum-- "because, for instance, there could be an explosion in the nucleus. I think November '85 is a good guess for the earliest nakedeye sightings.'

Earthlings will be studying every move Halley's makes, of course. The Japanese will send up two spacecrafts to measure its hydrogen halo, the European Space Agency's craft Giotto will meet the comet March 13, 1986, and the Soviet Union plans two space shots that will be aided by American antennas, in their attempt to close in on the phenomenon March 6 and 9 of that year. And in December American scientists announced they would have a cosmic dust analyzer aboard the Soviet Vega-1 and -2 spacecraft in the first Soviet-American joint space operation since 1975.

Though the United States will not be launching a special comet satellite, because of budget cutbacks, it will watch Halley's progress closely via the Pioneer Venus orbiter, the International Sun-Earth Explorer and the space shuttle. Three astronomers will board the shuttle in early 1986 with a sophisticated new telescope expected to take superb pictures of the head and tail. Three different ultraviolet telescopes also will be used.

What color is a comet? Pink. So they say. An astronomer, Fred Whipple, decided a few years ago the comet must be like a dirty snowball, an "icy conglomerate' of ice and various kinds of dust. The varying composition apparently has something to do with why some comets split in two, some explode and some burn up in the sun. At least 600 have been spotted from our planet, most of them on fabulously long orbits that bring them to us once in 100,000 or a million years or so and then back out past Pluto.

Some 100 shorter-term comets are known. The spectacular Encke has a 3.3-year orbit, which means it won't be around long. It loses so much debris and gas in the sun that it will die after about 1,000 trips. Halley's is an "intermediate,' one of only 7 known comets with an orbit between 50 and 200 years.

Comets come from a deep-freeze storage area on the outer fringes of the solar system called the Oort Cloud, where as many as 2 trillion nascent comets are milling around. It was from this cloud, named for a Dutch astronomer, that Halley's was pulled by Jupiter's gravity.

Wherever it came from, wherever it is going, Halley's Comet will be seen this time by more people than ever before. It will be, as they say, the experience of a lifetime.

Even that isn't enough for some people. One farsighted manufacturer is turning out T-shirts that say: "I'll See It in the Year 2061 Too!'

Photo: ICE, a comet-spotting satellite built by the European Space Agency, will rendezvous with the comet Giacobini-Zinner in September, then swing around for a long-distance appraisal of Halley's next March.

Photo: Astronomers at Palomar Mountain Observatory welcomed Halley's Comet back into our sphere of view in October 1982. By December this year, it will be visible to the maked eye--at least to those with 20-20 vision.

Photo: Comets have the ancient Greeks to thank for their name: kometes aster, meaning "hairy star.' Not all have tails, but many such as Ikeya-Seki (left), Comet West (Center) and Halley's Comet (right) display striking profiles to astrophotographers.
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Copyright 1985 Gale, Cengage Learning. All rights reserved.

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Author:Kernan, Michael
Publication:Saturday Evening Post
Date:May 1, 1985
Words:1588
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