Friday, February 8, 2013

Betelgeuse, Stellar Wind, and Exploding Eggs

"Supergiant Star Betelgeuse to Crash Into Cosmic 'Wall' "
Miriam Kramer, Space.com (January 25, 2013)


(From ESA / Herschel / PACS / L. Decin et al, via space.com, used w/o permission.)
"In about 5,000 years, Betelgeuse is going to run straight into a line of dust (left)...."

"The red supergiant star Betelgeuse in the famed constellation Orion is on a collision course with a strange wall of interstellar dust, with the clock ticking down to a cataclysmic cosmic smashup in 5,000 years, scientists say.

"A new image of Betelgeuse by the European Space Agency's infrared Herschel space observatory, shows that the star will crash headlong into a trail of space dust while speeding through its part of the cosmos at a blistering 18.6 miles (30 kilometers) per second. That's about 66,960 mph (107,761 kph).

"Betelgeuse is a giant star that makes up the left shoulder of the Orion constellation and can easily be seen from Earth with the unaided eye by observers in the Northern Hemisphere. The star appears as a reddish-orange light above and to the left of Orion's belt...."

Betelgeuse is roughly 640 light years away: fairly close on a cosmic scale, but sufficiently distant from Earth to make the coming collision a matter for curiosity, not concern.

Astronomers have been learning quite a bit about the universe, particularly in the last century or so. That's bothered some rather tightly-wound folks, but the Lemming doesn't mind knowing that there's a whole lot of time and space. And that's another topic.

What's That?

"... The new Herschel observatory image shows Betelgeuse as a bright disk surrounded by a shield-like arc of gas as it approaches an odd bar-like wall of dust.

"The curved 'shield' formations to the left of the star are actually structures shaped by Betelgeuse's solar wind - the charged particles each star emits and blows out into the galaxy, ESA officials said. But the wall of dust the star will crash into may be anything, from a filament linked to the galaxy's magnetic field to a stellar cloud. Scientists do not think the dust wall is part of the Betelgeuse star structure.

"After the first bow of solar wind hits the line of dust in 5,000 years, Betelgeuse itself should run into the bar 12,500 years after that...."

Scientists have quite a bit of time to study that whatever-it-is before the solar (stellar?) wind from Betelgeuse starts stirring it up. Based on previous experience, the Lemming suspects that folks will be surprised by what happens. Which is just as well, since if we knew everything humanity wouldn't have much use for curiosity. More topics.

Back to Betelgeuse: the star is really big, and has been running through its hydrogen at a phenomenal rate. Soon, it'll run out. Without hydrogen to keep its fusion 'fire' going, the core of Betelgeuse will start cooling down: and, more to the point, stop providing the pressure that keeps Betelgeuse from collapsing.

That's when things get interesting. As all that tonnage of star-stuff falls inward, the star's core heats up: a lot. The physics is a trifle complicated, but basically the collapsing star works like a whacking great diesel engine: fusing lighter elements into heavier elements and releasing a phenomenal amount of energy in the process. Not that diesel engines fuse nuclei together, the reactions in that case are chemical. And that's, you guessed it, another topic.

The Lemming was making a point. What was it? Diesel engines. Stellar physics. Energy. Right.

All that energy released by fusing elements together heats up the collapsing star's core. The effect is sort of like what happens when you microwave an egg: which the Lemming does not recommend. Except that instead of spattering hot egg, most of the star gets spattered into space. It's a spectacle best viewed from a safe distance: a couple dozen light years should be enough.

Unless scientists are wrong about most of stellar physics, which doesn't seem likely, Betelgeuse will explode 'soon.' That Space.com article says in about 1,000,000 years: which is 'soon,' compared to how long this universe has been around. On the other hand, Betelgeuse was shrinking faster than expected a few years ago. (June 10, 2009) Folks on Earth could be have a grandstand seat for the show 'sooner.' Again, by cosmic standards.

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2 comments:

Brigid said...

Hasn't a lot of this stuff already happened because of how long it takes light to get from there to here?

Brian Gill said...

Brigid,

Good point. Light that left Betelgeuse roughly 640 years ago is arriving now: so the collisions mentioned in that article should start in about 5,000 - 640 = 4,360 years. Roughly.

Then we'll be observing the wave fronts when they reach Earth.

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