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Moon, Jupiter, and Aldebaran

February 18, 2013

Jupiter is accompanied by an amazing collection of moons. They include a world covered by giant volcanoes, and another with an ocean of liquid water below its thin, icy crust.

But most of the giant planet’s 60-plus known moons are chunks of rock that are no more than a mile or two in diameter. Many of them have similar orbits and composition, suggesting that they’re bits of a few large bodies that were fractured by collisions with other rocky objects. One group has 16 known members, while another has 15.

These moons all follow odd orbits. And many of them orbit in the opposite direction from Jupiter’s rotation. That means they probably began as asteroids that orbited the Sun on their own, but were captured by Jupiter’s gravity.

The capture process isn’t easy — it requires something besides just Jupiter and the asteroid. For example, a thick cloud of gas and dust around the young Jupiter could have acted as a brake, helping to slow the asteroids into orbit. Or they could have been nudged into orbit by interactions with other asteroids. Regardless of the mechanism, these asteroids helped Jupiter gather the largest family of known moons in the solar system.

Look for brilliant Jupiter close to the right of our own Moon at nightfall. The star Aldebaran, the eye of Taurus, the bull, is a little closer to the lower right of the Moon. All three of them drop down the western sky later on, and set in the wee hours of the morning.


Script by Damond Benningfield, Copyright 2012

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