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Bright Contrasts

May 27, 2013

The planets Venus and Jupiter have a few things in common. They’re both members of our solar system, for example, and both are quite bright as seen from Earth — brighter than anything else in the night sky except the Moon. And you can see just how bright they are this evening, as they pose side by side quite low in the western sky shortly after sunset. Venus is the brighter of the two, with Jupiter just to the left.

For the most part, though, Venus and Jupiter are about as different as two worlds can be.

Venus is small and rocky, like Earth. It’s blanketed by a dense atmosphere of carbon dioxide that makes Venus the hottest world in the solar system — temperatures average about 860 degrees Fahrenheit. An unbroken layer of clouds made of sulfuric acid tops the atmosphere. These clouds reflect most of the sunlight that strikes them, which is one reason Venus looks so bright.

Jupiter, on the other hand, is a giant — the largest planet in the solar system. It’s about 12 times Venus’s diameter. It has a dense, rocky core, but most of the planet is made of hydrogen and helium, the two lightest chemical elements.

Like Venus, Jupiter is also blanketed by clouds — in Jupiter’s case, a mixture of water vapor, ammonia, and other compounds. They also reflect a lot of sunlight, helping the giant planet shine brightly.

A third planet stands above these two bright lights: Mercury, the smallest planet in the solar system. We’ll talk about it tomorrow.


Script by Damond Benningfield, Copyright 2013

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