University of Arizona
10 May 2000
TUCSON -- University of Arizona Spacewatch astronomers at Kitt Peak, Ariz., have rediscovered the last "lost" numbered minor planet, the Minor Planet Center located at the Smithsonian Astrophysical Observatory in Cambridge, Mass., demonstrated yesterday (May 9).
Until this month, asteroid 719 Albert has long eluded astronomers. It was last seen by direct observation in 1911, the year it was discovered by astronomer Johann Palisa (1848-1925) at the Imperial Observatory in Vienna, a world-class observatory of the pre-World War I Austro-Hungarian empire.
Palisa was using the observatory's prize 68-cm (27-inch) telescope when he discovered the new minor planet on Oct. 3, 1911. He observed it again on Oct. 4, as did an astronomer at Copenhagen Observatory, which had been notified of Palisa's find.
That was the last direct observation anyone had of 719 Albert, named for a baron who had donated generously to the Vienna Observatory. Until last week.
Jeff A. Larsen first detected asteroid 2000 JW8 -- now known to be 719 Albert -- with the .9-meter (36-inch) Spacewatch telescope early in his May 1 observing run. Larsen, a principal research specialist who joined Spacewatch three years ago, has dedicated most of his time to writing computer software for the telescope.
"This object was very faint, almost at the limits of what Spacewatch can do, and it wasn't moving all that fast," Larsen said. "But it caught my eye because it was moving differently from its neighbors. It moved like a near-Earth object."
Spacewatch director Robert S. McMillan and Spacewatch astronomer James V. Scotti observed the asteroid again on May 3 and May 6. They confirmed that the asteroid, officially named 2000 JW8, was an Earth-approacher. Yesterday, May 9, Michael Hicks and Ron Fevig of the UA Lunar and Planetary Lab observed the asteroid once more, this time using the 2.1-meter (84-inch) Kitt Peak reflector.
Gareth V. Williams, associate director of the Minor Planet Center (MPC), did the orbital calculations that showed 2000 JW8 is long-lost 719 Albert. MPC Director Brian Marsden reviewed the calculations and quickly concurred that, after 89 years, asteroid Albert had been rediscovered.
Astronomers now know the asteroid's orbit precisely. They know that most of the time, asteroid 719 Albert is 300 million miles or more from the sun, and that it makes a complete orbit around the sun every 4.28 years. It makes its closest swings by Earth every 30 years -- in 1911, 1941, 1971 and 2001.
"It's never going to hit Earth," McMillan said. The close approaches are between about 19 million miles and 29 million miles from Earth, or never closer than roughly a fifth the distance from the Earth to the sun.
Astronomers plan to learn more about the asteroid when it comes within 27 million miles of Earth on Sept. 5, 2001.
Scientists don't know for sure how large the asteroid is because they don't know how much light is reflected by the asteroid's surface material, McMillan added. Given its absolute magnitude, or absolute brightness, astronomers estimate that the asteroid is between 2 kilometers (1.24 miles) and 4 kilometers (2.5 miles) in diameter.
Astronomers have remained intrigued by the asteroid "partly because of the intellectual challenge of finding an object that has been lost for so long and comes close to Earth only once every 30 years," McMillan said.
The recovery has been "satisfying for Spacewatch, too, because we found the object when it was quite faint, more than a year before its closest approach to Earth," McMillan said. Spacewatch covers a relatively small area of sky, but it sees very faint objects farther out into the solar system than do other such surveys.
"Other asteroid surveys would have found this eventually, but finding it now gives astronomers time to apply for telescope time on larger telescopes for detailed observations of the asteroid," McMillan said.
"This has been exciting to me, because I've always been interested in classics in astronomy," Larsen said. "I have nothing but the greatest respect for those earlier astronomers. They actually had to look through the telescope lens to find their objects. They didn't have computers or CCDs.
"For me, when I first saw it, this was another unusual asteroid," he said. "It was Gareth Williams of the Minor Planet Center who made the identification. I owe him several beers."
UA Professor Tom Gehrels and McMillan founded the Spacewatch Project in 1980. It is a survey of the whole solar system, from the vicinity of Earth's orbit all the way out to beyond Neptune's orbit. The primary goal is to explore the various populations of small objects in the solar system and to study the statistics of asteroids and comets to better understand the dynamical evolution of the solar system. Spacewatch also finds potential targets for space missions, provides astrometric support for spacecraft mission planning, and finds objects that might present a hazard to the Earth. More information about Spacewatch can be found on the Spacewatch web site.
Back to ASTRONET's home page
Terug naar ASTRONET's home page