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Moon and Saturn

June 1, 2015

You’d think that after centuries of plotting the motions of the planets, astronomers would know the position of each world in our solar system down to the last millimeter. But that’s not quite the case — especially for the worlds of the outer solar system. The positions of those planets can be off by miles.

But thanks to a sort of interplanetary GPS, they’ve narrowed down the position of Saturn to a single mile.

Saturn is the second-largest planet in the solar system — almost 10 times wider than Earth. But, on average, it’s almost 900 million miles away. At that range, it’s difficult to pinpoint the planet’s position to less than a few miles.

Scientists have managed to do just that by monitoring radio signals from the Cassini spacecraft, which has been orbiting Saturn for a decade. Precise tracking as Cassini looped around Saturn and its moons helped pinpoint the center of the planet. It also provided a more accurate measurement of Saturn’s mass, and pinpointed the center of gravity of the system of Saturn and its moons.

The other planets react to Saturn’s gravitational pull, so the new measurements of Saturn’s mass and position will help provide better measurements of their mass and position as well — yielding a better understanding of the entire solar system.

And you can easily pinpoint Saturn tonight. It looks like a bright golden star close to the upper right of the Moon at nightfall, and stays near the Moon all night.


Script by Damond Benningfield, Copyright 2015

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