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Moon and Jupiter
In the field of astronomy, time changes everything.
Consider Jupiter, the largest planet in the solar system. It's to the lower left of the Moon at first light tomorrow, and shines like a brilliant star.
In ancient times, many thought of Jupiter as a heavenly manifestation of a god. Jupiter, in fact, was the king of the gods of Rome. But four centuries ago, Galileo looked at Jupiter with his first crude telescope and saw a tiny disk with smaller lights circling around it. He realized that it was a world like our own, orbited by small moons.
As telescopes improved, astronomers could see bands of clouds encircling the planet. The clouds prevented them from seeing anything below, however. In the early 1900s, some thought there could be a solid surface thousands of miles beneath the cloudtops, perhaps surrounded by oceans of liquid ammonia.
Today, the consensus is that Jupiter has a small, rocky core surrounded by layers of metallic hydrogen, topped by a layer of hydrogen and helium gas that's thousands of miles thick.
Yet even that picture is incomplete. The exact size and mass of the core are uncertain, for example. But once again, new technology is on the way. A new spacecraft will provide the best maps yet of Jupiter's magnetic and gravitational fields, revealing more details about its internal structure -- perhaps once again transforming our concepts of the giant planet.
More about Jupiter and the Moon tomorrow.
Script by Damond Benningfield, Copyright 2011