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Saturn at Opposition

May 18, 2015

The second-largest planet in the solar system is putting in a first-rate performance right now. Saturn will be at opposition on Friday, lining up opposite the Sun in our sky, which is the best time for watching the planet all year. It’s in view as night falls, remains in the sky all night, and shines brightest for the year, outshining all but a handful of planets and stars.

Saturn is second only to Jupiter in size and mass. It’s almost 10 times the diameter of Earth. It probably has a dense core of rock and metal, but most of its great bulk is made of hydrogen and helium, the two lightest chemical elements.

That indicates that Saturn and Earth were born in different regions of the solar system. Earth was born close to the Sun. The Sun’s heat vaporized ice and other materials with a low boiling point. The solar wind then blew away those materials, along with the leftover hydrogen and helium gas. So all that remained were chunks of rock and metal, many of which merged to form Earth and the other inner planets.

Saturn formed much farther from the Sun, where conditions were colder and calmer. The cores of Saturn and the other giant planets were built not only of rock and metal, but also of ices. As the cores grew, their gravity swept up vast amounts of gas, forming truly giant worlds.

And giant Saturn is low in the southeast as night falls, near the head of Scorpius, the scorpion. It looks like a bright golden star. More about Saturn tomorrow.


Script by Damond Benningfield, Copyright 2015

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