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SYFY WIRE Bad Astronomy

Ceiling Nebula Is Watching You Trick-or-Treat

By Phil Plait

My friend and astronomer Amy Mainzer sent me a funny picture the other day. Amy is the top banana for NASA's NEOWISE mission, which scans the sky, looking for near-Earth asteroids in the far-infrared part of the spectrum.

The Spitzer Space Telescope was a similar observatory, taking more detailed pointed observations of various targets. One such object was NGC 6888, the expanding cloud of gas and dust blown out by the star WR 136:

Amy claims it looks like a jack-o‘-lantern. I can agree, kinda. But if pressed, I’d say it looks a lot more like ceiling cat.

I guess it’s scary either way.

In real life it’s even scarier. The central star, WR 136, is a massive and feisty beast. It was born with at least 30 times the mass of the Sun but shed a lot of that material in an epic solar wind when it turned into a red supergiant star (like Betelgeuse) a quarter of a million years ago.

It then turned into what’s called a Wolf-Rayet star, an incredibly luminous blue supergiant. Its wind switched from slow to fast, plowing into the previously ejected material, slamming into it and sweeping it up. The star emits a lot of ultraviolet light, which causes the shell to glow.

The rippling you see in it is due to the lower density stuff slamming into the thicker stuff. This creates fingers or ripples of matter called Rayleigh-Taylor instabilities, which are common in such objects.

By the way, did I mention that the entire nebula is about 250 trillion kilometers across? 

WR 136 is still a beefy star, and doesn’t have much longer to live. Eventually, it’ll explode, a ginormously powerful supernova blast that will scream outward, catch up with the material in NGC 6888, and scatter it into the galaxy. Happily, the star is 5,000 light-years away, so we’re in no danger from it. But what a show that’ll be.

Because an octillion tons of superheated plasma barreling into space at thousands of kilometers per second disintegrating everything in its path is about the best Halloween treat I can give you.


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