[This year already seems to have more than its share of asteroid and comet stories, both real and fanciful. Here's the latest on newly-discovered space objects approaching the earth, from a NASA press release dated February 1, 1997.]
Two newly detected members of the Solar System -- a rare asteroid orbiting close to Earth and a distant comet making its only appearance -- mark the first discoveries of the year for a team of astronomers at NASA's Jet Propulsion Laboratory (JPL), Pasadena, CA.
The discoveries, reported Jan. 10 by JPL planetary scientists Eleanor Helin, Steve Pravdo, David Rabinowitz and Ken Lawrence, were made with the Near-Earth Asteroid Tracking (NEAT) system at Mt. Haleakala, Maui, HI. Since their initial sightings, both objects have become the focus of worldwide observations by astronomers in Japan, China, Australia, Canada, Italy and the Czech Republic.
"This asteroid is a member of a rare class of asteroids, called Atens, which stay within Earth's orbit most of their lifetimes," said Helin, principal investigator of the NEAT project. "The object has a high inclination to the plane of Earth's orbit -- 31 degrees -- the second highest inclination of all the Atens we've discovered."
Dubbed 1997 AC11, the asteroid probably measures about 600 feet in diameter. It is only the 24th Aten to be discovered in 21 years, since Helin found and named the first Aten in January 1976.
With orbits that are smaller than Earth's, and short periods, Atens are in the vicinity of Earth frequently. This closeness to Earth makes them more likely to impact the planet than other types of asteroids.
"Atens never wander far from the orbit of Earth and can cross Earth's orbit as many as four times a year," Helin said. "1997 AC11, for instance, has a period of 8/10ths of a year, or roughly 9.5 months. As we continue to observe it in coming months, we will be able to characterize its orbital path with more precision. With more precise data, we will be able to examine its potential for collision with Earth at some time in the future."
Along with the newest Aten, astronomers also discovered a new comet moving toward the Earth and Sun. Designated Comet 1997 A1, the celestial snowball is expected to make its closest approach to Earth on Feb. 6, passing at a distance of about 230 million miles, but remaining visible in the night sky for several months thereafter. During its closest approach, the newly discovered comet will be visible in the constellation of Cancer and brighten to a magnitude of about 18. Moderate-sized telescopes with CCD chips will be able to observe the comet, Helin said.
"This comet has traveled a long distance, originating in the Oort Cloud, a region far beyond Pluto's orbit which is believed to house trillions of incipient comets," Helin said. "It has a parabolic orbit, which means it will travel through our Solar System once and probably never be seen again. Parabolic comets do not present their calling cards before arriving in the inner Solar System. They appear without warning."
Low-resolution black-and-white images of both objects are posted on the Internet at the following URL:
Discoveries of very faint or distant objects are increasing due to the introduction of technologically advanced, fully autonomous CCD telescopes. The NEAT camera, for example, employs a very large, very sensitive 4,096-by-4,096-pixel CCD. The camera is installed on a 39-inch telescope operated at the summit of Mt. Haleakala by the U.S. Air Force. Total detections since NEAT began operations in late 1995 have climbed to more than 9,000 objects, of which more than 50 percent are new objects.
Original file name: CNI - Asteroid discov.final
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