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Brilliant Jupiter

October 27, 2011

The planet Jupiter is putting in its best appearance of the year. It’s at a point in its orbit known as opposition, which means it’s opposite the Sun in our sky. It rises around sunset and is in the sky all night. It’s brightest for the year, too — it far outshines all the true stars in the night sky. Look for it low in the east as night falls, and arcing high across the south later on.

Jupiter is the largest planet in the solar system. It’s also one of the brightest — not just because it’s big, but because it’s highly reflective. The clouds at the top of its atmosphere reflect a little more than half of the sunlight that strikes them. Only Venus is more reflective.

A planet-hunting satellite recently found that a giant world in another star system is just the opposite — it’s the darkest world yet discovered.

It’s known as TrES-2b. It orbits a Sun-like star that’s about 750 light-years away. The planet is a giant, like Jupiter. It’s only a few million miles out from the star, though, so its surface is heated to close to 2,000 degrees Fahrenheit.

Yet the planet reflects only about one percent of the starlight that strikes it. That makes it blacker than any planet or moon in our own solar system — blacker than coal.

The reason is a puzzler. The planet’s probably a ball of gas, like Jupiter is, so it should be pretty reflective. Some odd chemical compound must be absorbing the starlight — making the planet a dark giant.


Script by Damond Benningfield, Copyright 2011


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