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Moon and Jupiter

December 3, 2015

A solar system-in-miniature keeps company with the crescent Moon early tomorrow — a system anchored by Jupiter. The planet looks like a brilliant star. It rises just above the Moon in the wee hours of the morning, and they remain close together at dawn.

After the Sun, Jupiter is the largest object in the solar system — about a tenth of the diameter of the Sun. And it’s encircled by more than 60 known moons. The largest of them is bigger than the planet Mercury, and several of them are interesting worlds in their own right. One is covered by volcanoes, for example, while another has an ocean of liquid water not far below its icy crust.

Jupiter dominates this collection of worlds in the same way the Sun dominates Jupiter and the other planets — through its gravitational pull. It holds its entourage of moons in orbit like a miniature solar system.

Jupiter’s gravity is so strong, in fact, that it heats the planet’s interior to thousands of degrees. That heat migrates to the surface, so Jupiter bathes its moons with infrared energy. But its gravity isn’t strong enough to trigger nuclear fusion — the process that powers the stars. That’s because, despite its great heft, Jupiter isn’t massive enough to become a star. It would have to be about 80 times heavier to ignite the fires of nuclear fusion — giving the solar system the glow of a second star.

We’ll talk about the Moon and another planetary companion tomorrow.

Script by Damond Benningfield, Copyright 2011, 2015

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