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Dimming of Betelgeuse animation


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I took a photo of Betelgeuse in February 2019 just because it's a pretty star - Thought I'd take another to see if it really has dimmed as much as everyone says and the difference is very noticeable -

Crab nebula expansion has been captured:  

Yes, I think it's a difference in sky brightness between the two nights perhaps - I didn't want to "massage" the images too much though for fear of changing the intensity of betelgeuse artificially  

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52 minutes ago, markse68 said:

The background of the current image is a bit lighter than the older image so it’s even dimmer?

Yes, I think it's a difference in sky brightness between the two nights perhaps - I didn't want to "massage" the images too much though for fear of changing the intensity of betelgeuse artificially  :)

Edited by timwetherell
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It may still be a bit presumptuous to expect the big fellow to go bang in the near future.
He could well hang about for a few hundred, if not thousands of years yet.
I'm not sure I want to see  Orion's right shoulder turn into a moon like object shining in our night,
or daylight sky. It would be a sight to behold for sure, but I'm not that eager for it happen :sad:.
Ron.

 

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Apology to Tim for missing my appreciation for his comparison image showing
the brightness  variation of the big red one. The blinking really does bring the  remarkable dimming 
of the star.  Sorry buddy.
Ron.

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13 hours ago, barkis said:

It may still be a bit presumptuous to expect the big fellow to go bang in the near future.
He could well hang about for a few hundred, if not thousands of years yet.
I'm not sure I want to see  Orion's right shoulder turn into a moon like object shining in our night,
or daylight sky. It would be a sight to behold for sure, but I'm not that eager for it happen :sad:.
Ron.

 

I know what you mean Ron, It would be interesting to see but orion is such an iconic constellation it would be sad to see it without Betelgeuse!

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9 hours ago, timwetherell said:

I know what you mean Ron, It would be interesting to see but orion is such an iconic constellation it would be sad to see it without Betelgeuse!

Once Betelgeuse does go, it will be that bright I don’t think we’ll be seeing Orion at  all for a while but to see the result will more than make up for it 

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2 hours ago, Jiggy 67 said:

Once Betelgeuse does go, it will be that bright I don’t think we’ll be seeing Orion at  all for a while but to see the result will more than make up for it 

It would certainly be the brightest planetary nebula in the sky. I'm not sure how long it would be before it's angular diameter was resolvable in amateur telescopes though?

 

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1 hour ago, timwetherell said:

It would certainly be the brightest planetary nebula in the sky. I'm not sure how long it would be before it's angular diameter was resolvable in amateur telescopes though?

Well, picking a number at random let's say it needs to have an angular diameter of five arcseconds, or about 0.08 radians.  At 700 ly distant, that would be about 56 ly wide.  So I'm thinking it won't happen in most of our lifetimes :)

The relationship is linear, so if you think you only need it to be an arcsecond in diameter, that's a little over 11 ly.  Still pushing it a bit assuming that the molecules forming the PN probably aren't going to be reaching very large fractions of the speed of light.

All assuming I've done my maths correctly, of course :D

James

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Hmmm.  Not sure my maths can be correct.  Apparently M1 is 5.5 ly across and has an angular diameter of about 6 arc minutes on the longer axis, but it is much more distant than Betelgeuse (about ten times as far?).  I shall ponder on this to see if I can work out where I have gone wrong.  Possibly in the conversion of arcseconds to radians.

James

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Well, this computery thing on my desk tells me that I'm a numpty and five arcseconds is about 0.000025 radians.  That would give an actual diameter of 0.0175 ly.  Assuming a similar rate of expansion to M1, that would be much quicker.  Just over three years?

Or if you want it to be, say as big as Jupiter at opposition (about 50 arcseconds?), it would take around thirty years.

Someone else best check my maths again just to make sure I've got it right this time :)

Would the initial phase of expansion be much quicker though?  I don't know.  That could make a big difference.

James

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11 hours ago, JamesF said:

Or if you want it to be, say as big as Jupiter at opposition (about 50 arcseconds?), it would take around thirty years.

 

Yes, good idea to compare with the crab! I'd be thinking crab nebula 1000 years ago now 300 arcseconds across 0.3" per year. Ten times further away but because all the angles are small one can probably just use small angle approximation and say 3" a year (never did have a very comfortable relationship with radians! :D ) so maybe jupiter size in decade/s? I imagine it would be very bright though?

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