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(meteorobs) Excerpt from "CCNet, 94/2000 - 25 September 2000"
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From: Benny J Peiser <b.j.peiser@livjm.acdot uk>
To: cambridge-conference@livjm.acdot uk
Subject: CCNet, 25 September 2000
Date: Mon, 25 Sep 2000 12:11:37 -0400 (EDT)
CCNet, 94/2000 - 25 September 2000
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(1) DOUBLE TROUBLE: TWO NEW BINARY ASTEROIDS
Ron Baalke <baalke@zagami.jpl.nasadot gov>=20
[...]
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(1) DOUBLE TROUBLE: TWO NEW BINARY ASTEROIDS
>From Ron Baalke <baalke@zagami.jpl.nasadot gov>=20
http://www.skypub.com/news/news.shtml=20
Double Trouble: Two New Binary Asteroids=20
Sky & Telescope
September 23, 2000
It's been seven years since the Galileo spacecraft spotted=20
little Dactyl in orbit around minor planet 243 Ida, marking=20
the first iron-clad discovery of a binary asteroid. But=20
since then other such doubles have been identified, and the=20
list has just gotten two new entries: 762 Pulcova and 90=20
Antiope. William J. Merline (Southwest Research Institute)=20
and six colleagues captured Pulcova's pairing on February=20
22nd using the 3.6-meter Canada-France-Hawaii Telescope and=20
Antiope's on August 10th using the 9.8-meter Keck II=20
telescope. Both instruments were equipped with an=20
adaptive-optics system that minimized the effects of=20
atmospheric turbulence. (Merline also headed the team that=20
discovered a moonlet around 45 Eugenia in 1998.)=20
In an online abstract of a presentation to be made at a=20
planetary-science meeting next month, the team notes that=20
Pulcova's companion is about 4 magnitudes dimmer than its=20
140-km-wide parent, suggesting that it is perhaps 20 km=20
across. The moonlet circles Pulcova every 4.0 days at a=20
mean distance of about 800 km.=20
The situation with Antiope is more unusual because the two=20
components have nearly the same brightness, thus making=20
each roughly 85 km across. They are separated by just 170=20
km and complete one joint spin every 16.5 hours. Until now=20
dynamicists had assumed that asteroidal satellites were=20
most likely captured impact debris, but Antiope's=20
near-twins can't be explained so easily. Merline and his=20
team can't rule out a very thin bridge of material=20
connecting Antiope's twosome, but they think it unlikely.
Previous computer simulations by William Bottke (also at=20
Southwest Research Institute) hint that if an object is a=20
rubble pile it can be cleaved into halves by an impact or a=20
close encounter with a massive object.=20
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