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Moon and Jupiter

February 23, 2016

The Moon has a brilliant companion tonight. It looks like a big, fat star close to the upper left of the Moon as they climb into good view a couple of hours after sunset.

Despite that “stellar” appearance, though, Jupiter is really a planet — the biggest in the solar system. It’s about 11 times wider than Earth, and more massive than all the other planets combined.

Jupiter takes advantage of that great heft. The young solar system contained trillions of small comets and asteroids. But Jupiter’s powerful gravity hurled many of them out of the Sun’s domain. Some may have been captured by other stars, but most probably are wandering through the galaxy alone.

Jupiter continues that influence today. It alters the orbits of any comets or asteroids that pass anywhere near it. It flings many of them away from the inner solar system, to regions where they’re no threat to Earth. But it flings others toward the Sun and Earth, increasing the likelihood of a collision. So the planet can be both a protector and a nemesis to our own.

Jupiter’s gravity even has an effect on the solar system’s other planets, including Earth. Although Jupiter’s gravitational pull is tiny compared to that of the Sun, over time, its influence adds up. And when you combine that with the influences of the other planets, it means that astronomers can precisely project Earth’s orbit only a few tens of millions of years into the future — the blink of a cosmic eye.


Script by Damond Benningfield

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