M17
A giant stellar nursery arcs across the south on summer nights. It's part of a system that's given birth to thousands of stars in the last few million years, and is giving birth to many more even now.
The nursery is known as M17. It's a large cloud of gas that's lit up by several hot, massive stars.
M17 is a "blister" on the edge of an even bigger cloud -- a large, dark bubble of gas and dust that's expanding rapidly. As the bubble rams into the gas around it, it triggers the birth of new stars.
In fact, a team of astronomers recently found about 400 objects that are just beginning to shine as stars. And there could be several hundred more awaiting discovery.
The astronomers have come up with a possible timeline for M17.
It begins a few million years ago, when a dense clump of gas inside the giant cloud collapses and gives birth to several thousand stars. Radiation and "winds" from the hottest, brightest stars begin to carve a bubble in the surrounding cloud.
A couple of million years ago, the bubble hits another dense clump of gas, squeezing it together to form several hundred more stars. And in the last few hundred thousand years, the bubble hits yet another clump of gas, setting off the most recent wave of starbirth.
M17 is above the lid of the "teapot" formed by the brightest stars of Sagittarius, which is low in the south at nightfall. You need binoculars to spot M17 -- a faint smudge of light that's really a busy stellar nursery.
Script by Damond Benningfield, Copyright 2008
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