Betelgeuse Star undergoing rapid shrinking

[dragon]

Haven't seen this posted yet. Kind of cool might get a nova someday soon, in the cosmic sense.

One of the largest known stars in the universe is shrinking rapidly, and astronomers don't know why.

Betelgeuse (pronounced almost like "beetle juice") is a red supergiant star 600 light-years away in the constellation Orion. From Earth the star is clearly visible with the naked eye as the reddish dot that marks Orion's left shoulder.

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Researchers at the University of California, Berkeley, first measured the star in 1993 with an infrared instrument on top of Southern California's Mount Wilson. They estimated the star to be as big around as Jupiter's orbit around the sun.

But measurements made since then using the same instrument show that Betelgeuse has withered by 15 percent—a reduction in size roughly equal to the orbit of Venus—over the past 15 years.

The cause of the star's rapid contraction is a mystery. But the team noted that they had observed an unusual big red spot on the star three years ago.

"Maybe there's some kind of instability going on there," said study team member Charles Townes, a Nobel Prize-winning astronomer at the University of California, Berkeley.

"This red spot may be connected with the fact that [Betelgeuse is] gradually shrinking in size."

Collapse or Bounce Back?

A class of stars known as Mira variables are known to swell and contract by as much as 25 percent every two years—at their lowest points Mira stars can completely disappear from view.

Astronomers know how and why Mira stars pulsate, and they know that the pulses are linked to changes in the stars' brightness.

Betelgeuse is a type of variable star, with slight dips in its brightness every few years. (Find out why Betelgeuse is also called the Valentine's Day star.)

But its pulses are nowhere near as dramatic as those of Mira stars, the UC Berkeley researchers say. And on average the star is no fainter now than it was 15 years ago.

"Something unusual is happening with this star. The question is, What's going to happen next?" Townes said.

Betelgeuse is about 8.5 million years old, and astronomers predict it could explode as a supernova at any time. When it detonates, the blast should be clearly visible from Earth.

link

[Lord Relvenous]

Pretty much every time I go outside, I locate Betelgeuse, just in case it explodes while I'm looking at it. Cool article. I really hope it goes supernova in our lifetime. (Very unlikely, I know)

[Darkdrium]

600 lightyears huh? So technically, it could have already gone nova right?

What's the danger zone of a supernova for a star that size again ?

[Lord Relvenous]

We're fine. Despite what Star Trek says, a supernova cannot threaten the entire galaxy. All we'd get would be a pretty weeks long firework show.

[Guardsman Bass]

It would be quite a sight in the sky, if previous records of supernova witness have been accurate.

[Lord Relvenous]

Yeah, astronomers theorize that supernovae in the past has outshone the Moon, and that you'd be able to read a newspaper at midnight in it's light. That sounds awesome to me.

The "Star Crust Is Ten Billion Times Stronger Than Steel" story is pretty cool. It's about neutron stars, just a short blurb and somewhat obvious, but cool nonetheless.

[Ariphaos]

600 lightyears huh? So technically, it could have already gone nova right?

What's the danger zone of a supernova for a star that size again ?

Something like eight light years. There isn't a star close enough to be a serious threat, really.

[starslayer]

Um, no, the danger zone is more like 50 ly. In any case, a Betelgeuse* supernova would be brighter than the Full Moon, easily visible during the daytime, and could possibly cast shadows during the day too (that last bit I'm not at all sure about, though). However, since it would be a single point, unlike the Moon, it would probably make your eyes water looking at it; and you probably would be able to read a newspaper with its light**. Amateur astronomers like me would marvel at it for a few weeks, watching it reach maximum brightness and taking lots of pictures, and then curse it as we can't observe anything else for the next year.

*It's pronounced "bettle-jews," not "Beetlejuice." It's probably a corruption of the Arabic for "armpit of the mighty one."

**I say newspaper and not book because a book's print would likely be too small. Try reading one during a full Moon and see.

[Lord of the Abyss]

*It's pronounced "bettle-jews," not "Beetlejuice." It's probably a corruption of the Arabic for "armpit of the mighty one."

As I understand it, almost everyone including astronomers pronounces it "beetlejuice" regardless of the technically correct pronunciation. I recall an article by Isaac Asimov on just that subject in fact.

[Surlethe]

Split spam posts.

[starslayer]

As I understand it, almost everyone including astronomers pronounce it "beetlejuice" regardless of the technically correct pronunciation.

I hear both a lot, in both the amateur and professional communities (though, I admit, I've never had many occasions to hear a professional astronomer disucss the star). Yeah, it seems most do pronounce it like the name of Keaton's ghost, but I try to gently correct them where possible. I don't touch stuff like Virgo, though (technically, it's pronounced "weer-go," but I don't care).

[Broomstick]

This may be a dumb question but hey, I'm not an astrophysicist. Could this contraction be a preliminary to a nova event?

[RedImperator]

This may be a dumb question but hey, I'm not an astrophysicist. Could this contraction be a preliminary to a nova event?

It could indeed. If this is the final gravitational collapse underway, then very shortly Betelgeuse will blow itself apart. On the other hand, we know so little about very old red giants that this could just be something that red supergiants do periodically.

[starslayer]

If the final collapse were underway, it'd have blown up by now. For a star like Betelgeuse, these are the various burning timescales:

-H -> He: ~1E8 yr
-He -> C, O: ~1E7 yr
-C, O -> Ne, Mg, etc.: ~300 yr
-assorted products -> Si, et al.: ~6 months (IIRC)
-Si, et al -> Fe via nuclear statistical equilibrium (NSE)*: ~2 days
-Fe -> n: ~1 second
BANG!

*The Coulomb barrier for silicon fusion is so high that the nuclei would photodisintegrate before the temperature was high enough to overcome it; thus, the silicon nuclei simply grab extra alpha particles and neutrons and grow until they become iron nuclei. This process is called nuclear statistical equilibrium, or NSE. Once the core is mostly iron, the temperature is so high that the background blackbody photons start blowing apart iron nuclei into 13 alpha particles and a couple extra neutrons. This is an unstable endothermic process, leading to a loss of energy in the core and a collapse into a neutron star. As indicated above, this final step takes place in about one second.

[The Duchess of Zeon]

If the final collapse were underway, it'd have blown up by now. For a star like Betelgeuse, these are the various burning timescales:

-H -> He: ~1E8 yr
-He -> C, O: ~1E7 yr
-C, O -> Ne, Mg, etc.: ~300 yr
-assorted products -> Si, et al.: ~6 months (IIRC)
-Si, et al -> Fe via nuclear statistical equilibrium (NSE)*: ~2 days
-Fe -> n: ~1 second
BANG!

*The Coulomb barrier for silicon fusion is so high that the nuclei would photodisintegrate before the temperature was high enough to overcome it; thus, the silicon nuclei simply grab extra alpha particles and neutrons and grow until they become iron nuclei. This process is called nuclear statistical equilibrium, or NSE. Once the core is mostly iron, the temperature is so high that the background blackbody photons start blowing apart iron nuclei into 13 alpha particles and a couple extra neutrons. This is an unstable endothermic process, leading to a loss of energy in the core and a collapse into a neutron star. As indicated above, this final step takes place in about one second.

Would contraction be indicative of the beginning of any of the prior stages?

[Patrick Degan]

If the final collapse were underway, it'd have blown up by now. For a star like Betelgeuse, these are the various burning timescales:

-H -> He: ~1E8 yr
-He -> C, O: ~1E7 yr
-C, O -> Ne, Mg, etc.: ~300 yr
-assorted products -> Si, et al.: ~6 months (IIRC)
-Si, et al -> Fe via nuclear statistical equilibrium (NSE)*: ~2 days
-Fe -> n: ~1 second
BANG!

*The Coulomb barrier for silicon fusion is so high that the nuclei would photodisintegrate before the temperature was high enough to overcome it; thus, the silicon nuclei simply grab extra alpha particles and neutrons and grow until they become iron nuclei. This process is called nuclear statistical equilibrium, or NSE. Once the core is mostly iron, the temperature is so high that the background blackbody photons start blowing apart iron nuclei into 13 alpha particles and a couple extra neutrons. This is an unstable endothermic process, leading to a loss of energy in the core and a collapse into a neutron star. As indicated above, this final step takes place in about one second.

Would contraction be indicative of the beginning of any of the prior stages?

This seems more characteristic of the death-throes of a star of our type: departure from the main sequence, expansion to red giant stage, a period of contraction and a secondary expansion, then pulsations as the star begins sloughing off its outer layers as the fusion processes are exhausted. Perhaps we are seeing the first such contraction in this process. Though this shouldn't be happening with a star of 15+ solar masses.

Betelgeuse may end up redefining several established parametres of stellar lifecycles, unless we've guessed wrong about the nature of the star we've been observing since the Arabs first named it.

[starslayer]

Goddamn it, drop an OOM from the first two burning stages. No, Betelgeuse will not live over 100 million years! It's in relatively old age right now.

Would contraction be indicative of the beginning of any of the prior stages?

No. While the core contracts slowly during each burning phase, and much more rapidly during the transitions, it heats up in doing so (all that GPE has to go somewhere, after all). This causes the outer layers to puff up. Betelgeuse started out as a blue star, but on its way to core helium burning, it puffed up as the core contracted. It did so again when it started core carbon burning. After that, the burning timescales are so short that the radiation simply doesn't have time to push the envelope out, and we see nothing. However, after the initial hydrogen burning stage, fusion doesn't just happen in the core. There are shells around the core that continue to have the right conditions for various burning processes. Interactions between them are what cause the pulsations we see. Something else altogether weird and unknown is causing the current shrinking of Betelgeuse, likely connected with the large "spot" seen on its surface, as noted by the astronomer quoted in the article.

This seems more characteristic of the death-throes of a star of our type: departure from the main sequence, expansion to red giant stage, a period of contraction and a secondary expansion, then pulsations as the star begins sloughing off its outer layers as the fusion processes are exhausted. Perhaps we are seeing the first such contraction in this process. Though this shouldn't be happening with a star of 15+ solar masses.

Betelgeuse may end up redefining several established parametres of stellar lifecycles, unless we've guessed wrong about the nature of the star we've been observing since the Arabs first named it.

But you would observe a much stronger solar wind if that were the case. Betelgeuse does have a strong stellar wind (as all AGB stars do), but it has not actually lost any more mass than normal, from what I gather; rather, the envelope is physically shrinking quite rapidly for some reason. Usually, this would indicate a large loss of core luminosity, but the star has not dimmed noticeably beyond its normal variation. Something very odd is going on here.

[Fingolfin_Noldor]

I have never heard of the expansion and contractions during the helium phase to be so distinct that you could see a sizable contraction this far away and this slow. This is also a point in the star's life where things get really bright as it burns most of its usable fuel at a drastic rate just to stay in gravitational/photon pressure equilibrium.

Moreover, if the external layers actually get expelled, we should actually see a halo around it, but we aren't.

Now I will not put it past the idea that our existing models need some tweaking of the parameters, and I will be actually glad to see some actual raw data of a near by supernova going off. Not since the one that created the Crab nebula have we actually gotten any raw data.

[starslayer]

I have never heard of the expansion and contractions during the helium phase to be so distinct that you could see a sizable contraction this far away and this slow. This is also a point in the star's life where things get really bright as it burns most of its usable fuel at a drastic rate just to stay in gravitational/photon pressure equilibrium.

I know. This most certainly is not the aftermath of a shell flash event.

Now I will not put it past the idea that our existing models need some tweaking of the parameters, and I will be actually glad to see some actual raw data of a near by supernova going off. Not since the one that created the Crab nebula have we actually gotten any raw data.

We find supernovae, and get raw data from them, almost every day in surveys. What we have little data on is the progenitor stars. That is where Betelgeuse will be most helpful.

[Fingolfin_Noldor]

We find supernovae, and get raw data from them, almost every day in surveys. What we have little data on is the progenitor stars. That is where Betelgeuse will be most helpful.

We probably do, but nothing this close. I don't think Betelgeuse constitutes as a progenitor star though. Though what is the current definition for them? Are they the "first stars" that lead on to super massive singularities or the "first stars" in the galaxy?

[Razaekel]

If the current collapse of Betelgeuse doesn't fit standard models of astrophysics, then from what I see, there's two possibilities: either the standard models need revision, or there are external factors at work here. Occam's razor says we should accept the simplest possible explanation for this behavior, which is that there is something unaccounted for in the standard models. But for a bit of a hypothetical exercise, what external factors could cause this sort of rapid collapse, if any?

[Fingolfin_Noldor]

If the current collapse of Betelgeuse doesn't fit standard models of astrophysics, then from what I see, there's two possibilities: either the standard models need revision, or there are external factors at work here. Occam's razor says we should accept the simplest possible explanation for this behavior, which is that there is something unaccounted for in the standard models. But for a bit of a hypothetical exercise, what external factors could cause this sort of rapid collapse, if any?

This issue here is not that it is a rapid collapse, but rather it is this slow. Everyone expected that the final collapse would be rather fast and furious, with material falling back towards the iron core and get expelled out. And this process actually generates a huge bulk of the heavy elements which otherwise normal fusion in the star would never produce (because the huge amount of energy and compaction that occurs in the rebound).

This rather slow contraction contradicts generally accepted models. I am not too familiar with the data from known supernovae and whether they have shown this slow contraction or not, but most of what I have read seems to imply that nothing has contradicted the existing model too much beyond tweaking the parameters. Of course, having a supernova blow up this close will probably generate more data than the average supernova just by the sheer quantity of light that will arrive here.

[Executor32]

I think by progenitor stars, starslayer was referring to the stars that preceded the supernovae we have data on, as we don't tend to notice them until after they've gone supernova and become just a tad easier to see.

[Hawkwings]

Well, considering how absolutely HUGE Betelgeuse is, this "slow collapse" may have some other factors involved that are slowing it down.

Size comparison:
http://video.google.com/videoplay?docid ... 1713172831

[dragon]

Well, considering how absolutely HUGE Betelgeuse is, this "slow collapse" may have some other factors involved that are slowing it down.

Size comparison:
http://video.google.com/videoplay?docid ... 1713172831

Jeesh those stars at the end are huge.