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StarDate 5/12/2014: Saturn At Opposition

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FROM THE UNIVERSITY OF TEXAS McDONALD OBSERVATORY, AS HEARD ON KCBS RADIO WEEKDAYS @ 9:52 A.M., 7:35 P.M. & 2:52 A.M.

STARDATE 5/12/2014: The second-largest planet in the solar system is putting in a first-rate performance this month. Saturn, which is second only to Jupiter, lines up opposite the Sun in our sky. It rises around sunset, scoots low across the south during the night, and sets around sunrise. The planet is well to the lower left of the Moon this evening, and looks like a brilliant golden star.

Saturn shines so brightly in part because it’s closest to Earth right now, at about 825 million miles. But Saturn’s brightness also depends on the angle at which we see its broad, beautiful rings.

The rings are made of small bits of rock and ice, along with sheets of dust. If you put all that debris together, you’d have enough to make a small moon, which wouldn’t be an impressive sight. Instead, though, it’s spread out over billions of square miles, so it reflects a lot of sunlight.

How much sunlight depends on the viewing angle. Like Earth, Saturn is tilted on its axis. As it orbits the Sun, it appears to “nod” up and down. So at times, we see the rings edge on, so they’re barely visible at all. At other times, though, they’re tilted up or down a good bit, so we see much more of them, which makes Saturn look much brighter to the eye alone.

Right now they’re tilted at a pretty good angle. That angle will get even better over the next few years, so Saturn will shine even brighter in the years ahead.

We’ll have more about Saturn tomorrow.

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