Findings in space occur at a blur

SUN JOURNAL

Astronomy: Computers and digitized optics have discoveries occurring faster than they can be agreed upon.

November 25, 2001|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

When most of us learned about the solar system back in grade school it was a simple place, as familiar and seemingly permanent as the block we grew up on.

There was the sun, and its family of nine planets - from broiling Mercury out to icy Pluto. Some of us could label the sprinkling of moons, paste a belt of asteroids between the orbits of Mars and Jupiter, or sketch in a handful of wandering comets, with tails blazing.

And we could be pretty sure the picture wouldn't change much before high school.

But those days are gone.

Thanks to the development of more-sensitive electronic cameras, and high-speed computers, the roster of the known solar system grows by the thousands every month.

"Business is certainly booming," said Brian Marsden. His business, as director of the International Astronomical Union's Minor Planet Center, in Cambridge, Mass., is to verify and catalog all the new discoveries as they pour in.

These new finds include thousands of comets and asteroids, a lengthening list of new moons, and icy new worlds orbiting in the dim, remote realm beyond Pluto.

Astronomers, in their efforts to impose order, have assigned their discoveries to a growing, and increasingly bewildering, list of at least 36 celestial tribes and sub-tribes.

Closest to Earth are the Atens, Apollos and Amors, classes of asteroids that cross or approach Earth's path. They are also frequently referred to as Near-Earth Asteroids or Potentially Hazardous Asteroids. (Since 1991, five have zipped past Earth at distances closer than the moon.)

Between Mars and Jupiter there are the Hungarias, Floras, Phocaeas and at least 17 other classes of asteroids.

Past Jupiter are the Trojans, Centaurs, Cubewanos, Plutinos and Scattered Disk Objects. Many cruise in the icy "Kuiper Belt," or "Trans-Neptunian Belt" beyond Neptune, where Pluto is king, and the distinctions between comets and asteroids blur.

Some categories are purely theoretical.

`Overdone it a little'

Vulcanoids, Apoheles and Arjunas, for example, are clans of asteroids that orbit close to the sun - some inside Mercury's path, none moving beyond Earth. Except that not a single representative has ever been confirmed.

"I think we've overdone it a little," Marsden said. There have been calls for a convention to clean up the much-debated mess, he said, but "it never seems to get done. I don't know whether we'd even get agreement."

Who has time? The discoveries are relentless.

In the 2000 edition of Peterson's Stars and Planets field guide, Jupiter was listed as having 16 moons. In January, astronomers at the University of Hawaii reported finding 11 more. All appear to be captured asteroids, ranging in size up to about 5 miles in diameter.

Last year's Peterson's also counted 18 moons for Saturn, and 18 for Uranus. But astronomers have since discovered four more moons orbiting Saturn, and three more around Uranus - none bigger than 100 miles in diameter.

Comets?

"It used to be, a few decades ago, we'd expect to find a half-dozen a year," Marsden said. "Now we're finding maybe a half-dozen a month."

Professional astronomers and amateurs alike are finding them regularly in the dark night sky. And since the mid-1990s, NASA's Solar and Heliospheric Observatory - a satellite that stares unblinkingly toward the sun - has serendipitously spotted more than 300 new "sungrazing" comets in the daytime sky, 70 of them this year alone.

Two years ago the total number of officially cataloged comets was 1,036. Today the number is approaching 1,400, Marsden says.

But it is the asteroid hunters who have truly struck it rich.

The first asteroid, Ceres, was discovered on the night of Jan. 1, 1801. By 1938, the count had reached about 1,500.

"There was a resolution to the IAU 40 years ago asking, `Why don't we stop cataloguing when we get to 3,000?'" Marsden said.

Instead, the search accelerated, driven by growing interest in what the movement and makeup of asteroids might tell science about the birth of the solar system, and by worry about a potential civilization-ending collision with Earth.

By the start of 1999, the count of asteroids that have been given official numbers had reached 10,000. It reached 20,000 by the start of this year. This month, it topped 30,700.

Data on new observations pour into Marsden's office at a rate of 16,000 a month.

Most turn out to be new sightings of old objects. But about 1,000 a month seem novel enough to get an official number. If the orbits hold up in subsequent observations, they'll eventually get names.

More than three-quarters of the discoveries have been made by the Lincoln Near Earth Asteroid Research project. But amateurs contribute, too.

And still that's not all.

In 1977, Charles Kowal, an astronomer at Mount Palomar in California, spotted a peculiar new object. It looked like an asteroid, but it was crossing planetary orbits between Jupiter and Neptune like a comet. And in 1988, it developed a tail as ices began to warm and escape from its surface.

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