Comet is breaking up in race toward Jupiter

April 13, 1994|By Frank D. Roylance | Frank D. Roylance,Staff Writer

Fragments of the shattered comet Shoemaker-Levy are breaking up as they rush toward their predicted collision with Jupiter in July, but their discoverer still predicts "lots of fireworks" when they hit.

Dr. Eugene Shoemaker said yesterday that the latest photographs of the "string of pearls" comet, taken last month, show that one fragment "has actually winked out and another component has become double."

As sharper photos have come in, estimates of the sizes of the 10 largest fragments have been scaled down from a range of a maximum of 2.7 miles in diameter to as little as 0.6 of a mile.

"The 10 largest fragments might be as small as a kilometer [0.62 miles] across," said Dr. Shoemaker, scientist emeritus at the U.S. Geological Survey.

"But that's still plenty big enough to give us lots of fireworks."

He spoke before a conference on low-cost planetary missions at the Johns Hopkins University Applied Physics Laboratory in Laurel.

Shoemaker-Levy, once a 6-mile-wide ball of ice and dust, is believed to have been broken apart by gravitational forces during a July 1992 pass by Jupiter. The fragments -- at least 21 of them -- have been flying in formation since then, appearing like a string of pearls or headlights along a highway.

They reached their farthest point from Jupiter last July, and are now about halfway back, stretched across millions of miles of space, and accelerating.

Dr. Shoemaker, his wife, Carolyn, and astronomer David Levy discovered the comet in March 1993. By last summer, they realized that its orbit would send it crashing into the giant gaseous planet in a seven-day series of collisions beginning July 18.

The resulting flashes and fireballs are expected to release energy on Jupiter that would dwarf the largest nuclear war that humans could ever unleash on Earth.

Humans will feel no apparent effects from the impacts and will see nothing without a telescope. The blasts will be 480 million miles away, and just beyond Jupiter's horizon as seen from Earth.

But astronomers are preparing the Hubble Space Telescope and ground-based observatories to watch for light and heat from the blasts reflected by the planet's moons or the comet's own dusty halo. As Jupiter revolves, they'll watch clouds at the impact sites for ripples and hot spots that could reveal much about the planet and about comets.

Budget cuts have shut off a camera on the distant Voyager 2 spacecraft that would have had a direct view. But the Galileo, Ulysses and Clementine spacecraft now on interplanetary missions will be watching.

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