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Polaris Flare

August 20, 2015

Stars are born in vast clouds of gas and dust. Astronomers can study the very first stage of starbirth by observing clouds that haven’t yet given birth to any stars. One such cloud is in the far northern sky, near the North Star, Polaris. It’s called the Polaris Flare.

Its exact size and distance aren’t known, although it’s probably about 400 to 800 light-years from Earth, and probably spans about a hundred light-years. It consists mostly of molecular gas — the cold, dense type of gas that’s most likely to create new stars.

So far, though, the Polaris Flare has yet to spawn a single star. With no stars inside to warm it up, the cloud is frigid — around 430 degrees below zero.

Still, it contains hundreds of dense clumps of gas. Many of these clumps may disperse, with their gas simply filtering away into space. But some of them may be the kernels of future stars.

These dense knots of material may collapse under their own weight. As that happens, the gravitational energy of the collapse is converted into heat, so the object begins to glow — and a new star is born.

In any event, the Polaris Flare gives us the chance to observe an interstellar cloud before its star-making career begins.

Although the gas cloud is invisible to the eye, Polaris is not. To find it, line up the two stars at the outer edge of the Big Dipper’s bowl. Extend that line above the bowl until you come to the first moderately bright star: Polaris.


Script by Ken Croswell, Copyright 2015

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