M5

StarDate: May 12, 2009

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Many of the stars in our region of the galaxy are fairly young -- from a few million to a few billion years old. Most of the really old stars congregate in what might be called stellar retirement centers. Their stars are as old as the galaxy itself -- up to 13 billion years.

One of these retirement centers is in the east on May evenings. Through binoculars, it looks like a fuzzy round blob of light, with a bright star-like core. But it's really a family of several hundred thousand stars -- a globular cluster known as M5.

The stars of M5 all formed from the same dense cloud of gas and dust when both the galaxy and the universe were quite young -- less than a billion years after the Big Bang. As the cluster aged, its heavier stars used up their nuclear fuel. The heaviest ones exploded, while lighter ones lost their outer layers, leaving behind only their small, faint cores. But stars that were no more massive than the Sun continued to shine on.

Today, several hundred thousand of these stars are packed into a ball that's only about 150 light-years across. That means the stars are far closer together than they are in our own galactic neighborhood. So the night sky from a planet in M5 would be filled with stars -- the last members of a stellar retirement center.

M5 is in the constellation Serpens Kaput -- the tail of the serpent. It's well up in the east a couple of hours after nightfall. You need binoculars and a starchart to find it.

Script by Damond Benningfield, Copyright 2009

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