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Uranus at Opposition
The young solar system was crowded, busy, and sometimes violent. It contained not only today’s planets, but many other planet-sized bodies. Some were thrown clear of the solar system by the gravity of Jupiter and the other giant planets, while others were hurled into the Sun.
But a few rammed into today’s planets, with impressive results. A collision between Earth and another body may have given birth to the Moon. Another collision may have caused Venus to spin backwards. And yet another may have pushed the giant planet Uranus over on its side.
Uranus is the third-largest planet in the solar system — four times the diameter of Earth. So it would have taken quite a wallop to push it over — or perhaps two wallops. Research published a few years ago suggested that the planet got hit not once, but twice. The second impact was needed to help produce the orbits of Uranus’s moons.
But a couple of years earlier, another group of researchers said you wouldn’t need a collision at all. Instead, interactions between Uranus and a giant moon could have tilted the planet over. The gravity of another planet could then have yanked the big moon away, leaving Uranus as we see it today.
And in fact, right now is a good time to see this giant planet. It lines up opposite the Sun, so it rises at sunset and is in view all night, in the constellation Pisces. It’s so dim, though, that you’ll need binoculars to pick out.
More about Uranus tomorrow.