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Shibby

Betelgeuse Imaged

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I think this image was actually produced back in November, so sorry if it's already been posted here somewhere, but it's NASA's APOD today:

APOD: 2010 January 6 - The Spotty Surface of Betelgeuse

The actual disc & surface of the star resolved using interferometry. Nice.

Keck (which didn't produce this image) can also be used as a massive interferometer, I'm trying to find some of Keck's results, will post them here when I do...

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Fascinating. I do wonder if a typical star has surface features

ROUGHLY like our Sun - Scaled up or down... or not. :)

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I can't wait for it to happen.

Every time I look at Betelgeuse I think "do it now please". On the other hand, if it happened now, it would still take over 400 years for us to see it.

So in reality I'm hoping that it happened long enough ago so that we will be able to see it any time soon. What a wonderful sight that will be.

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I would expect the shape of Betelgeuse to be quite irregular - prior to going bang - although a face on image it does suggest that this is the case.

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It's a fascinating subject, aperture synthesis - a method commonly used by radio telescopes to produce images, but also used by optical interferometers. Here's some more interesting images and results for you to chew on...

Capella resolved by COAST, the Cambridge Optical Aperture Synthesis Telescope:

COAST: Downloadable files

COAST Imaging of Betelgeuse and Alpha Herculis:

COAST: Astronomical results

IOTA (Infrared Optical Telescope Array) images of Betelgeuse before it closed:

CfA Press Room

NPOI (Navy Prototype Optical Interferometer) including movie of binary star Mizar:

Science

VLTI (Very Large Telescope Interferometer)

ESO - Paranal Telescopes Overview - VLTI

Edited by Shibby

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Am i right in saying Betelguese is a variable star?. I never knew this before. I know that it is approx 400 times larger then our Sun. I mean when observing variable stars how the hell can you guys tell the difference in magnitude?.

OK sure i have seen Betelguese on different nights and it looks brighter on one night then others. I just put down to seeing conditions etc.

Edited by LukeSkywatcher

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Am i right in saying Betelguese is a variable star?

Indeed, a "semi-regular variable" star. Here's a chart on wikipedia of its brightness over the period Dec. 1988 - Aug. 2002: File:Light curve of Betelgeuse.png - Wikipedia, the free encyclopedia

Apparently, it's also shrunk in diameter by 15% in the last 16 years and some believe this is the start of its gravitational collapse.

Edited by Shibby

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When it goes Foom!, how fast do these things blow? I mean, would we just notice it was a bit brighter for a few hundred years as it gradually expands?

Or would we be looking at Orion one day and wonder where the new neb had come from?

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Thanks Shibby. Yeah i have heard that it has shrunk quite a bit in the last few years. I wonder if we will see it go bye bye in our lifetime.

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When it goes Foom!, how fast do these things blow? I mean, would we just notice it was a bit brighter for a few hundred years as it gradually expands?

Or would we be looking at Orion one day and wonder where the new neb had come from?

Hmm...

A quick google tells me that the supernova ejecta could travel up to 30,000km/s, but it's 2x closer to us than M42, so it would expand to the approximate angular size of the orion nebula (which 12 lightyears across) in about 60 years after exploding, by my calculations.

M42: 1344 ly away, 12 ly across

Betelgeuse: 640 ly away, could expand at up to 1 ly every 10 years.

12 * (640/1344) * 10 = 57 years

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Thanks Shibby, nicely explained. I guess it's going to be a slow-goer then, but noticeable relatively quickly; even if it 'did the big firework' today (or rather 640 years ago), we'd still be in for a wait to see something like M42.

Cheers :)

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Thanks Shibby, nicely explained. I guess it's going to be a slow-goer then, but noticeable relatively quickly; even if it 'did the big firework' today (or rather 640 years ago), we'd still be in for a wait to see something like M42.

There would be a burst of neutrinos, which we'd probably detect on Earth and would be the first sign. A few days later, the star would brighten very rapidly (few hours) as the shockwave burst through the surface of the star. Then it would brighten more over the next few weeks as the explosion expands (resolvable with interferometers/8-meter AO, but not small telescopes). After a couple of weeks, the gas would start to cool, and the supernova would begin to fade. It would take several years to get back down to the current brightness of Betelgeuse. By then, you may just be able to start seeing the expanding nebula in good seeing...

The nebula would be more like M1 (A supernova that went off in 1054) rather than M42 (a star forming region).

Would certainly jump right to the top of "what should I look at" lists :)

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Enjoyed reading this post as I love the though of all this..

Would I be right in saying the the star could already gone nova in the last 640 years but we are yet to see it as it takes time for the light etc to get to us...

Just quite new to this and want to conf my understanding...

Cheers

Teddy

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Yep - if it is 640 Light years away it will take 640 years for the light to get to us, so what we see now are the photons exiting back then.

Chris

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Thanks Chris

Without hijacking the thread

..... How does the solar eclipse work then

If the light takes 8min or so to reach us from the sun and we all stand and watch the moon cover the sun up. am I right in saying that what we are watching is not now it's 8min or so in the past. So the sun and the moon are not where they are when the eclipse is full etc.

I hope u understand what I mean.

So everything we look at that in space is the past.....

Aarrrggghhh it's crazy ... Help lol

Teddy

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not really...

The sun light you see is indeed about 8 minutes "old".

But during an eclipse it's the Moon that makes it happen. So you only need to take into account the time it takes light to travel from the Moon to Earth, which is just over 1 second if I remember correctly. So you see the shadow with about 1 sec delay.

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arrgghhh

I should not have missed that..

Thanks , every little step forward in knowledge helps

Teddy

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