Word: moonlet
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Dates: during 1990-1999
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...repeat itself. Stars orbit the pivot point at the center of galaxies, planets in turn orbit stars, and moons in turn orbit planets. Last week astronomers writing in the journal Nature announced that this cosmic reductionism goes even further. For the first time, ground-based telescopes spotted a tiny moonlet orbiting a mere asteroid in Earth's own solar system...
...Hawaii discovery did not mark the first time a moonlet had been found around an asteroid. In 1993 the Galileo spacecraft sped past the 20-mile-wide asteroid Ida and spotted a scrap of moon just under a mile wide circling it. But the only way Galileo could detect the tiny target was to fly there across many millions of miles of space and do its exploring up close. Now, thanks to new optics in the CFHT, it's possible to search for moonlets from the comfortable perch of a faraway Earth...
Already the discovery of the moonlet is paying scientific dividends. By analyzing the orbit of the satellite, astronomers are drawing surprising inferences about the composition of Eugenia itself. Most asteroids are thought to be about three times as dense as water, but Eugenia is barely 20% denser, suggesting it either is made of loosely packed rubble or is rich in ordinary ice. Further analysis could help settle the question, and more discoveries of more moonlets could shed similar light on Eugenia's asteroid-belt sisters...