|
|
This page contains recent press releases concerning discoveries and information about minor planets (asteroids) and related issues. The page will be updated as and when time permits.
Previous Articles - 2000
[January]
[February]
[March]
[April]
[May]
[June]
[July]
[August]
[September]
[October]
[November]
[December]
Previous Articles - 1999
[January]
[February]
[March]
[April]
[May]
[June]
[Return to Home Page]
A Binary Asteroid, Close to Home
A small asteroid now passing near Earth has revealed one of its secrets: it's actually two asteroids. A team of six radar astronomers led by Lance A. M. Benner and Steven J. Ostro (JPL) has found that 1999 KW4 is a double body whose components are separated by at least 2 km. Based on their observations from May 21-23, announced yesterday on IAU Circular 7632, one half is at least three times the size of the other. But neither piece is thought to be more than 2 or 3 km across.
Observers have suspected that 1999 KW4 might be double since last June. That's when Petr Pravec and Lenka Sarounova (Ondrejov Observatory, Czech Republic) recorded a very peculiar light curve with brightness fluctuations of 0.1 to 0.2 magnitude, suggesting that the little asteroid rotates in about three hours. But, as detailed in the June 2001 issue of Sky & Telescope, Pravec couldn't get the data from individual nights to fit together in a simple way. Further high-quality photometry by Italian amateur Vittorio Goretti did not solve the mystery either. The radar team plans to continue its probing of the interloper through May 29th using the Deep Space Network's 70-meter tracking antenna at Goldstone, California. Benner adds that for the run's last four days they will attempt a series of interferometric observations, using the 305-meter Arecibo radio antenna in Puerto Rico to transmit pulses of radio energy and both dishes to receive the asteroid's reflected echoes. These studies should yield some clue as to the makeup of this object, which comes within 30 million kilometers (0.2 astronomical unit) of the Sun at perihelion. Backyard observers have a chance to spot 1999 KW4 this weekend, as it will come as close as 4.8 million kilometers to Earth (and it won't be in our vicinity again for another 18 years). At its brightest the asteroid will be near 11th magnitude, putting it within the grasp of 4-inch or larger telescopes. For details on where and when to see it, go to http://www.skypub.com/sights/skyevents/0105skyevents.shtml. [Return to Index][Top of Page][Return to Home Page]