[meteorite-list] Sky & Telescope News Bulletin - May 25, 2001
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:46:25 2004
SKY & TELESCOPE'S NEWS BULLETIN - MAY 25, 2001
For images and Web links for these items, visit http://www.skypub.com
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
SAHARAN SANDS YIELD MORE EXOTIC METEORITES
The desolate sands of the western Sahara have yielded yet another bumper
crop of unusual meteorites. As detailed in July's Meteoritical Bulletin and
announced on May 23rd, within the last few months six new samples from the
Moon and Mars have come into the possession of African meteorite hunters.
The half-dozen finds range in size from 104 to 633 grams. According to Ron
Baalke, a veteran collector, the Martian meteorite Northwest Africa 817 is
significant because it is the fourth example of a nakhlite (a basaltic
subtype) ever found -- and the first since 1958.
In recent years the Sahara has proven a fertile hunting ground for
meteorites of all types, raising the number of recognized lunar finds to 23
and Martians to 18. Many of these are "paired" multiples, a situation where
fragments of a single fall are found close together (but not necessarily at
the same time). Even though teams of meteorite-hunting scientists from the
U.S. and Japan still trek to Antarctica every year, the plains of western
Africa seem to be yielding more than their share of exotic finds. Part of
the reason, says Jeffrey N. Grossman, who edits the Meteoritical Bulletin,
may be that the Antarctic teams bring back every meteorite they spot,
whereas private dealers can be more selective when they want to have their
Saharan stones analyzed and certified. "Nobody will classify hundreds of
boring ordinary chondrites," Grossman notes, "so the dealers pick out the
ones that can make them money and get scientists to look just at those."
COMET LINEAR (C/2001 A2)
Despite having broken into two, then three pieces, Comet LINEAR remains
brighter than 6th magnitude -- though only visible from Southern Hemisphere
skies. It's about 20 deg. above the west-southwest horizon after evening
twilight, and observers report that it has a striking tail at least 3
degrees long. Unfortunately, this comet will not be visible from the
Northern Hemisphere until late June. It reached its closest point to the
Sun, at a distance of 117,000,000 kiloemters, on May 24th. Here are
coordinates for Comet LINEAR (C/2001 A2) at 0 hours Universal Time for the
May 25 5h 21m -25.5 deg.
May 27 5 15 -26.0
May 29 5 8 -26.5
May 31 5 1 -27.0
Copyright 2001 Sky Publishing Corporation. S&T's Weekly News Bulletin
and Sky at a Glance stargazing calendar are provided as a service to
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Received on Fri 25 May 2001 04:49:39 PM PDT