Betelgeuse is one strange place

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pmn1

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Betelgeuse shrinking??

http://blogs.discovery.com/space_disco/ ... thing.html

June 10th 2009

If there's one thing I've realized when writing articles about space, is that it is very easy to link a mysterious astronomical phenomena with doom. If not doom for Earth, certainly doom resulting in a huge explosion of some kind, destroying something, somewhere...

Mystery = Doom

Let's look at a very simple example: In 1983, NASA's Infrared Astronomical Satellite (IRAS) carried out the first ever space-based survey of the entire sky at infrared wavelengths.

IRAS spotted some mystery infrared objects (make a note of the word "mystery"). This would be expected, I suppose, as this was the first survey of its kind.

The Washington Post picked up on NASA's initial findings and published an article entitled "Mystery Heavenly Body Discovered," in which the author lays out some possibilities for these infrared objects. Initial reports postulated that one of these objects could be a long-period comet, or a planet, or a far-off young galaxy or a protostar.

Innocent enough, you may think. However, this one news article planted the seed of an entire Planet X doomsday scenario that has given root to countless YouTube videos, doomsday books and now, a Sony Pictures movie, to be released in November.

It's of little concern to doomsday "believers" that these mystery infrared objects were identified as ultra-luminous young galaxies far, far away, and not a nearby Earth-killing "Planet X". Doomsday theories stick, no matter how much evidence there is to the contrary.

Shrinking Stars and Supernovae

So, today I read about the incredible observation by astronomers that the famous red supergiant star Betelgeuse is shrinking. According to University of California, Berkeley astrophysicists, over the last 15 years, Betelgeuse has shriveled by 15% in diameter.

This is a startling observation in my opinion. Although the star has undergone no variation in luminosity, to be able to distinguish a 15% reduction in size of a star some 600 light years away is astonishing. The supergiant isn't even an "easy" star to observe; as it's so old, it's undergoing some violent changes, blasting hot gas into space, shrouding its surface from view. Only by using the extremely sensitive Infrared Spatial Interferometer (ISI) on the top of Mt. Wilson in Southern California, researchers were able to see through the haze and measure the star diameter with such precision.

On reading through the Berkeley press release, there is no mention that this shrinkage could indicate Betelgeuse is about to explode. Granted, the 15 year shrinkage is a "mystery" (there's that word again), but the star has been known to vary in size in the past. In fact, it is known to pulsate in size with periods of one and six years. Also, the rotational period of Betelgeuse is once every 18 years; simulations suggest the star is not spherical, so the shrinkage could be an illusion, we are seeing a potato-shaped disk on its thinnest edge.

Despite all these factors, Fox News runs with the title "Nearby Star May Be Getting Ready to Explode." Using the Berkeley press release as a source, and quoting all the facts mentioned above, they've put two and two together, made five and declared stellar Armageddon.

Oh dear.

They've also made their own prediction right at the end:

It's possible we're observing the beginning of Betelgeuse's final collapse now.

If so, the star, which is 600 light-years away, will already have exploded — and we'll soon be in for a spectacular, and perfectly safe, interstellar fireworks show.

Yes, it's totally possible Betelgeuse could explode, but the chances of this happening in this 600 year window is highly unlikely, regardless how fast it seems to be shrinking.

Needless to say, the Fox article has done the best on the social bookmarking sites, hitting the front page of Digg. Everyone loves a supernova. As for the "shrinking star" reports, not so much.

This may not have the makings of the next, great doomsday movie plot, but it is an example how definite conclusions (i.e. a supernova) can be made from a fairly benign, yet interesting astronomical "mystery".

Sources: AFP, FOX, UCB, Universe Today
 
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michaelmozina

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Re: Betelgeuse shrinking??

From the original article:

Despite Betelgeuse's diminished size, Wishnow pointed out that its visible brightness, or magnitude, which is monitored regularly by members of the American Association of Variable Star Observers, has shown no significant dimming over the past 15 years.

It is perplexing enough that it has changed size so dramically, but the fact it shows no significant dimming over that same time frame is more than a little weird. I haven't a clue how it could loose 15% of it's size and not show a significant change in brightness over that same timeline.
 
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michaelmozina

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Re: Betelgeuse shrinking??

I guess my first question is how exactly are they measuring the diameter of the object. The specific wavelength seems to make a big difference here as it relates to the physical size of the star.
 
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harrycostas

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Re: Betelgeuse shrinking??

G'day from the land of ozzzzzz

This also could be a cyclic event.
 
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michaelmozina

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Re: Betelgeuse shrinking??

harrycostas":1vei99wi said:
G'day from the land of ozzzzzz

This also could be a cyclic event.

Hey Harry, great to see you here. I think you'll enjoy this neck of the woods.

I guess the mystery is how it shrinks and/or grows and yet we do not observe a drastic change in total energy output.
 
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yevaud

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Re: Betelgeuse shrinking??

pmn1":1qsuzg7v said:
It's possible we're observing the beginning of Betelgeuse's final collapse now.

Indeed it looks as if it may be. While everyone is hedging their bets a bit - not coming right out and definitively saying it's an imminent Supernova - it is the number one possibility.

As everyone knows, a star is basically a balancing act between gravity pulling inwards, and fusion pressures pushing outwards. A constant luminosity yet a 15% decrease in size (and the rate of shrinking is increasing, btw) in that time frame means the fusion core of Betelgeuse is losing the battle with gravity. It's probably exhausted Hydrogen, and is working it's way onwards from there.

The constant luminosity is odd, but the shrinking is incontrovertible. Btw, Harry, stars of this type are not known to have cyclical shrinkings/expansions. Changing luminosity, yes.

Timeframe: any time within the next 1,000 years, and we may see the closest Supernova ever witnessed.
 
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nimbus

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Re: Betelgeuse shrinking??

So the irregular sphericity was ruled out?
 
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MeteorWayne

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Re: Betelgeuse shrinking??

Not sure what you mean by irregular sphericity. I've never heard that term before. Can you explaain a bit?

Oh and BTW, nothing's been ruled out. This is the first time such observations of any star has been possible, so it's all unknowns right now. It's a matter of fitting the observations into existing theory, of finding out that some new idea is needed to explain what is being observed.

Cutting edge science!
 
K

kg

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Re: Betelgeuse shrinking??

nimbus":317yxxcl said:
So the irregular sphericity was ruled out?

This bit is from the article...

"Granted, the 15 year shrinkage is a "mystery" (there's that word again), but the star has been known to vary in size in the past. In fact, it is known to pulsate in size with periods of one and six years. Also, the rotational period of Betelgeuse is once every 18 years; simulations suggest the star is not spherical, so the shrinkage could be an illusion, we are seeing a potato-shaped disk on its thinnest edge."

I think this is what your asking about. Looks like it's not ruled out.
 
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yevaud

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Re: Betelgeuse shrinking??

That is truly unusual behavior for a Red Giant, as I understand it, not typical at all. One wonders if it might be yet another manifestation of approaching collapse and Supernova?
 
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nimbus

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Re: Betelgeuse shrinking??

MeteorWayne":34x7qo4t said:
Not sure what you mean by irregular sphericity. I've never heard that term before. Can you explaain a bit?
Layman lingo :p KG's quote is what I was referring to.
 
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xXTheOneRavenXx

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Re: Betelgeuse shrinking??

If Betelgeuse IS potato shaped, then is it the poles that are elongated or the equator? If it's the poles, then could this be caused by an increased magnetic field intensity that may be associated with it nearing the collapse phase? or another means of exhausting matter into space?
 
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michaelmozina

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Re: Betelgeuse shrinking??

yevaud":31scpbp3 said:
pmn1":31scpbp3 said:
It's possible we're observing the beginning of Betelgeuse's final collapse now.

Indeed it looks as if it may be. While everyone is hedging their bets a bit - not coming right out and definitively saying it's an imminent Supernova - it is the number one possibility.

As everyone knows, a star is basically a balancing act between gravity pulling inwards, and fusion pressures pushing outwards. A constant luminosity yet a 15% decrease in size (and the rate of shrinking is increasing, btw) in that time frame means the fusion core of Betelgeuse is losing the battle with gravity. It's probably exhausted Hydrogen, and is working it's way onwards from there.

The constant luminosity is odd, but the shrinking is incontrovertible. Btw, Harry, stars of this type are not known to have cyclical shrinkings/expansions. Changing luminosity, yes.

I guess the thing that doesn't add up for me about the idea of a supernova is the notion of a stable luminosity. I would expect that any drastic change in the core's stability would almost necessarily result in a change in energy output. The notion it's shrinking is related to a supernova events seems reasonable, but then I would expect to see a significant change in luminosity, if only due it's drastically reduced surface area.

Timeframe: any time within the next 1,000 years, and we may see the closest Supernova ever witnessed.

Well, lets hope it's sooner rather than later or we will all miss the party. :)
 
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yevaud

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Re: Betelgeuse shrinking??

michaelmozina":21rurfjz said:
I guess the thing that doesn't add up for me about the idea of a supernova is the notion of a stable luminosity. I would expect that any drastic change in the core's stability would almost necessarily result in a change in energy output. The notion it's shrinking is related to a supernova events seems reasonable, but then I would expect to see a significant change in luminosity, if only due it's drastically reduced surface area.

I'd wager the reason is, the fusion effects may take what, a thousand years, to migrate outwards such that we see an increase in luminosity. On the other hand, alterations in magnetic field and physical dimensions might take place at a much faster rate. And a few other random thoughts about possibilities that I'll spare everyone.

michaelmozina":21rurfjz said:
Well, lets hope it's sooner rather than later or we will all miss the party. :)

Count me in!
 
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FreeThinkingAnarchist

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Re: Betelgeuse shrinking??

FOX New's viewers are mostly too old and uninformed. They can say anything they want and don't need to consider facts.
 
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MeteorWayne

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Re: Betelgeuse shrinking??

What does that have to do with the conversation?

If you'll note I posted a link to the original report a post or so later.
 
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trumptor

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Re: Betelgeuse shrinking??

It's interesting to think, I recently spent an evening showing my son where the constellation Orion is, and where Betelgeuse is within the constellation. We can look at it and talk about it, but in reality it may have already gone supernova a hundred years ago and we have absolutely no idea. In the night sky its still twinkling and looks as intact as ever.
 
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michaelmozina

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Re: Betelgeuse shrinking??

It is interesting when you think about it that way.
 
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xXTheOneRavenXx

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Re: Betelgeuse shrinking??

That would almost definately explain why we don't see a change in the energy output... yet. To us this could be just the first stages the star is going through before it's output is affected during it's transition.
 
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michaelmozina

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Re: Betelgeuse shrinking??

xXTheOneRavenXx":2itkb2xf said:
That would almost definately explain why we don't see a change in the energy output... yet. To us this could be just the first stages the star is going through before it's output is affected during it's transition.

Well, I agree, it's probably the most likely reason it's shrinking, but even then the fact that the overall output hasn't changed much even with a 15 percent change size and significant change in surface volume does seem perplexing even in that scenario. I guess I'd expect to see some sort of change in the total output during the shrinking process.
 
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xXTheOneRavenXx

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Re: Betelgeuse shrinking??

It's just an idea, but what if the energy output IS changing? I mean this in sense that as the star decreases in size, the energy output increases by the equivelant to keep it's energy output equalized during this phase. This would be best explained as the star trying to maintain a balance to prevent collapse, and the balancing energy output is a bi-product of this action. Yet another means of exhausting it's energy. I am not an expert on stars by any means. Just when I read everything that's been happening with Beatleguese, it just sounds to me like this may be the "best-fit" explaination.
 
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CalliArcale

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It's probably not that strange as red supergiants go, but it sure looks weird from the perspective of someone used to our quiet little Sun. ;-) Astronomers have made the best direct image yet of Betelgeuse and spied a phenomenally huge plume of material coming off of it.

Unveiling the true face of Betelgeuse
 
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MeteorWayne

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Have to look at the article in detail later, Calli, but this might best be merged into the recent Betelguese thread.

Betelgeuse, Betelgeuse, Betelgeuse... :)
 
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