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SKY & TELESCOPE'S NEWS BULLETIN
APRIL 2, 1999

THE MEASURE OF EROS

Had things gone according to plan, NASA's Near Earth Asteroid Rendezvous spacecraft would now be snugly in orbit around minor planet 433 Eros. But last December 20th a botched rocket firing caused the spacecraft to sail past its target. The unintended flyby wasn't devoid of scientific results, however. According to investigator Joseph Veverka, NEAR acquired images of Eros good enough to resolve features roughly 400 meters across. Overall, the asteroid measures a very elongated 33 by 13 by 13 kilometers. Veverka adds that the flyby was close enough (3,827 km) and slow enough (965 meters per second) to alter NEAR's trajectory very slightly. These deviations were barely measurable by tracking stations, but they allowed orbital specialist Donald Yeomans to determine that Eros has a mass of about 7 trillion tons and a bulk density near 2.5 grams per cubic centimeter. This density is similar to that of asteroid 243 Ida and much higher than that of 253 Mathilde, whose interior is apparently very porous. A careful search by NEAR turned up no satellites circling Eros any larger than 50 meters across. NEAR will close in for another attempt to orbit Eros on February 14, 2000.


Copyright 1999 Sky Publishing Corporation. S&T's Weekly News Bulletin and Sky at a Glance stargazing calendar are provided as a service to the astronomical community by the editors of SKY & TELESCOPE magazine. Widespread electronic distribution is encouraged as long as these paragraphs are included. But the text of the bulletin and calendar may not be published in any other form without permission from Sky Publishing (contact permissions@skypub.com or phone 617-864-7360). Updates of astronomical news, including active links to related Internet resources, are available via SKY & TELESCOPE's site on the World Wide Web at http://www.skypub.com/.

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