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One of the goals of modern astronomy is to see as far back in time as possible -- to see the universe as it existed shortly after the Big Bang, more than 13 billion years ago.
Yet you don't have to look across great distances to see remnants of that ancient era. In fact, you can see two of them tonight in the constellation Hercules. They're not billions of light-years away, but thousands -- on the fringes of our own galaxy.
These remnants are known as globular clusters. They're families of hundreds of thousands of stars packed into a ball that's only a few dozen light-years across.
The stars in these clusters are among the oldest in the universe.
Astronomers know the ages of these stars in part because of their composition. The stars contain very few "heavy" elements, which are manufactured in the hearts of stars. When stars die, they spew these elements into space, where they can be incorporated into new stars. Each generation of stars has more of these heavier elements, so stars with almost none of them must be very old.
Most models of this process say the stars in globular clusters are around 13 billion years old, which means they formed less than a billion years after the Big Bang.
Hercules is in the eastern sky by mid-evening, marked by a faint pattern of four stars called the Keystone. One of the globulars is near the top left corner of the Keystone, while the other is to the left of this pattern.
More about these clusters tomorrow.
Script by Damond Benningfield, Copyright 2010