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Old 12-27-2019, 03:35 PM
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Is Orion going to have a bum shoulder?


Betelgeuse, normally one of the brightest stars in the sky, has been steadily dimming over the past two months, to the point itís no longer in the top ten for magnitude.

Betelgeuse is a red super-giant, and thereís speculation that the sudden dimming could be a sign ITíS GONNA BLOW! If it does, it would be the first supernova in our galaxy since Keplerís time, early in the 17th century.

Likely could be visible by daylight, or as bright as the moon at night.

Or it could all just be a hiccup and nothing will happen for 800,000 years.

Will be fascinating if we do get to see it.

Couple of news articles:

https://www.cbc.ca/news/technology/b...ming-1.5407038

https://www.forbes.com/sites/startsw.../#45680d1d47bf
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Old 12-27-2019, 03:40 PM
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Serious question: how we know it hasn't already? Or don't we?
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Old 12-27-2019, 03:46 PM
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Say it three times fast. Would be quite a show.
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Old 12-27-2019, 03:59 PM
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Serious question: how we know it hasn't already? Or don't we?
Since information can only travel at the speed of light and Betelgeuse is believed to be 640 light years away whatever we're seeing now happened 640 years ago.

So it if pops off in reality that happened 640 years ago and we're just seeing it now.
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Old 12-27-2019, 03:59 PM
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It could have happened, but would be undetectable until the light and neutrinos arrive.

When we look at stars, we are always looking into the past, but from our frame of reference, it’s the present.
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Old 12-27-2019, 04:18 PM
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If we were in the way of the beam-type explosion ó which we're not ó or if Betelgeuse was a lot closer, we'd be in trouble.
How the hell do they know for sure we're not "in the way of the beam-type explosion"???

Damn, I'm going to have seconds on pie tonight.
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Old 12-27-2019, 04:28 PM
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This article has a nice illustration of BJ's size compared to our solar system.
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Old 12-27-2019, 04:36 PM
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How the hell do they know for sure we're not "in the way of the beam-type explosion"???

Damn, I'm going to have seconds on pie tonight.
Seconds on pie is always a good idea, regardless the state of the universe.
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Old 12-27-2019, 04:39 PM
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Oh great. That thing had BETTER blow up, and soon! If it doesn't, Mr VOW will make my life a pure Hell for the next 10,000 years!


~VOW
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Old 12-27-2019, 04:53 PM
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To see it would be fantastic. I mean, it's going to happen -- may as well happen while I get the chance to see it!

I wonder how long will the brightness will remain for us to observe?
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Old 12-27-2019, 04:54 PM
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If there's a beam, it'll be along the axis of rotation. We know we're not along Betelgeuse's axis of rotation, because it gets starspots (similar to sunspots), which cause small but detectable changes in brightness as they rotate on and off the portion of the surface that face us. We wouldn't see that if the axis is pointed towards us, because if it did, we'd always see the same hemisphere.

And yes, there's a good chance that even if we don't see it blow imminently, we might see it blow sometime in the next 640 years. Which in turn means that there's a good chance that it has in fact already blown. It's one of the very few, possibly the only, naked-eye star for which that's true.
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Old 12-27-2019, 04:55 PM
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I wonder how long will the brightness will remain for us to observe?
The timescale on which supernovas fade is on the order of months.
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Old 12-27-2019, 04:59 PM
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The timescale on which supernovas fade is on the order of months.
Thank you.
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Old 12-27-2019, 05:34 PM
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Here's a better view of the relative sizes of some stars including the Armpit of the Central One (or whatever translation of Betelgeuse you like).

https://en.wikipedia.org/wiki/File:Star-sizes.jpg

As the images make clear, you should gather up some pie and a lawn chair and a sleeping bag, and settle in for quite a show.

My money says a few hundred years worth of pie is about right for a first estimate.
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Old 12-27-2019, 07:18 PM
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After the particle storm sweeps away 90% of Terrestrial life, any surviving human culture will worship The Burning God whose laser projector cools at His shoulder. Believers will offer themselves for ritual immolation. Water will be damned. The Burning God wants us hot! Burn, baby, burn!
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Old 12-27-2019, 08:34 PM
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To see it would be fantastic. I mean, it's going to happen -- may as well happen while I get the chance to see it!
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The timescale on which supernovas fade is on the order of months.
Would it be better to see it right away, though? Will there be a sudden burst at the beginning, or gradually getting brighter and then gradually dimming?
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Old 12-27-2019, 08:39 PM
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A sudden burst, I think? But Chronos is the expert so will wait for his comment.
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Old 12-27-2019, 09:52 PM
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When astronomers say a Supernova is ‘imminent’’ they are talking about timescales measured in thousands to hundreds of thousands of years. It could go off today, or 10,000 years from now.
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Old 12-27-2019, 10:17 PM
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I wonder how long will the brightness will remain for us to observe?
Or how long we will remain to observe the brightness.
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Old 12-27-2019, 10:24 PM
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Or 1,000,000. Most of what we know about Betelgeuse is approximate. It could be 640 light years away, but that's plus or minus a few hundred light years. We do not know its size for sure - it is certainly a red giant and will go supernova some day, but the time frame for that is dependent upon its size, and our guesses on that have a pretty wide margin of error, too. Its size determines its lifespan, and if you don't really know the former you don't know the latter. It could have already gone poof and we'll see it by Easter, or it might not go poof for a length of time beyond human imagination.

Of course, I sure hope it goes now, because it would be a sight unlike anything else - brighter than the Moon, visible during the day, something unlike any celestial object most humans have, or will ever get, to see.
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Old 12-27-2019, 11:04 PM
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Agreed. It really would be something to see. Odds are probably against us, though. {{sigh}}
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Old 12-27-2019, 11:05 PM
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We only see Orion in the winter. If it happens in the summer time, would we see it at all?
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Old 12-28-2019, 12:32 AM
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And now i’ve got Bruce Cockburn’s “When the Sun Goes Nova” running through my head.

https://m.youtube.com/watch?v=NClz-kqL82A
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Old 12-28-2019, 04:33 AM
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We only see Orion in the winter. If it happens in the summer time, would we see it at all?
If the supernova is bright enough to be seen in the daytime yes, we would see it in summer. It's still there, we just can't see it for the same reason we can't see other stars in the daytime.
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Old 12-28-2019, 05:12 AM
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I hope it already happened, close to 640 years ago. I've got places to go, and a finite amount of pie.
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Old 12-28-2019, 01:07 PM
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How suddenly does such an event happen? Does a star just abruptly go kablooie over a span on, say, one hour? Or one week? Or one year? Or one hundred years?
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Old 12-28-2019, 01:53 PM
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We only see Orion in the winter. If it happens in the summer time, would we see it at all?
Orion is a 'winter' constellation in that it only rises at night in winter in the northern hemisphere. During winter Orion is on the same side of the sun as we are, so at night when we are facing away from the sun it appears in the night sky. In summer Orion on the other side of the Sun, so the only time it is in our field of view is during the daytime.

A Betelgeuse supernova would be bright enough to see during the daytime, just as the moon is. But it would be really spectacular at night.
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Old 12-28-2019, 02:17 PM
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Betelgeuse has always been kind of explody, but you know it is a variable star, right?

How long it takes... do you mean the actual core collapse? Milliseconds? You don't want to be around, let's say.
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Old 12-28-2019, 02:41 PM
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Not quite milliseconds: the outer part of the core collapses at up to 70000 km/s. But then it blows....

Last edited by DPRK; 12-28-2019 at 02:44 PM.
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Old 12-28-2019, 05:31 PM
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There are a variety of types of supernovas*. Details vary. But within a few seconds a huge percentage of remaining fussionable material does just that. Due to intense radiation and heat a lot of stuff keeps doing it's glow thing for a while, but the big excitement is over.

* Sorry, but I was born slightly after the Roman Empire collapsed.
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Old 12-28-2019, 05:33 PM
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Orion is visible at some time during the night through most of the year. We only consider it a "winter" constellation because in the northern hemisphere, winter coincides when Orion happens to be up through most of the night. Most other times of the year except for around June-July you can catch Orion while it's dark out but it might be some inconvenient time in the morning before it rises.
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Old 12-30-2019, 04:59 PM
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It seems to me that there is a general misunderstanding about what now means in relativistic terms among the participants: the 640 (light-)years are irrelevant. Now is when we see it, there is no absolute time in the Universe out there. We don't know and can't know anything before we can measure it, and we can't measure it before the signal arrives. But when the signal arrives, I want to look up. I hope it will be amazing. And fast in its development. I think it will be a joy to watch.
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Old 12-30-2019, 10:35 PM
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There are a variety of types of supernovas.*

* Sorry, but I was born slightly after the Roman Empire collapsed.
Right. As if the mere fall of a continent-spanning empire is a valid reason to give up on the rules of grammar. {{pffft}}
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Old 12-30-2019, 11:04 PM
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The timescale on which supernovas fade is on the order of months.
Which really puzzles me about an alleged supernova sighted in 1006, which was visible for about two weeks.
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Old 12-31-2019, 05:30 PM
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Which really puzzles me about an alleged supernova sighted in 1006, which was visible for about two weeks.
The months long thing is for an observer in the ~immediate vicinity. An observer quite far off will only see the very peak brightness which might last a few days. (But said observer with a good telescope will see it for longer.)

The inverse-square law applies to supernovas.
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Old 12-31-2019, 05:55 PM
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But aren’t all Earth-bound observers the same distance from a supernova?
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Old 12-31-2019, 08:08 PM
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But arenít all Earth-bound observers the same distance from a supernova?
I believe that ftg was talking about hypothetical observers around stars closer to the supernova than Sol.
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Old 01-01-2020, 08:45 AM
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But arenít all Earth-bound observers the same distance from a supernova?
Not all supernovas are the same distance from Earth-bound observers.
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Old 01-01-2020, 02:36 PM
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According to the Wiki article, the Big B is a variable star and normally varies from about 0.00 to +1.3 (faintest). Each order of stellar magnitude, by definition, is 2.5 so at the bottom of its normal variation it's already more than twice as faint as when it's at its brightest.

So what I'd l like to know now is just how faint Betelgeuse is at the moment. What is the current magnitude?

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Old 01-01-2020, 03:12 PM
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Each order of stellar magnitude, by definition, is 2.5 ...
Good point, but a minor nitpick: The logarithmic magnitude scale is based not on 2.5, but on 2.5118... (the fifth root of 100), so magnitude 5 is 100x dimmer than magnitude 0. The reason for this odd choice is historical. The magnitude scale is more than 2000 years old and originally had no precise mathematical definition. In the 19th century the modern definition was introduced to approximately match the historical magnitudes.
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Old 01-01-2020, 04:31 PM
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Good point, but a minor nitpick: The logarithmic magnitude scale is based not on 2.5, but on 2.5118... (the fifth root of 100), so magnitude 5 is 100x dimmer than magnitude 0. The reason for this odd choice is historical. The magnitude scale is more than 2000 years old and originally had no precise mathematical definition. In the 19th century the modern definition was introduced to approximately match the historical magnitudes.
Thanks for clearing that up. I knew I was overlooking some minor detail but I couldn't put my finger on it.

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Old 01-01-2020, 06:50 PM
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According to the Wiki article, the Big B is a variable star and normally varies from about 0.00 to +1.3 (faintest). Each order of stellar magnitude, by definition, is 2.5 so at the bottom of its normal variation it's already more than twice as faint as when it's at its brightest.

So what I'd l like to know now is just how faint Betelgeuse is at the moment. What is the current magnitude?

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It's apparently at the bottom of the historic range, with a +1.294 reading on the 20th. Meanwhile Sky and Telescope's Bob King writes that to him it seemed it may be approaching +1.5 at the end of December, down from 0.5 as late as October.

Last edited by JRDelirious; 01-01-2020 at 06:51 PM.
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Old 01-01-2020, 07:36 PM
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Which really puzzles me about an alleged supernova sighted in 1006, which was visible for about two weeks.
It would have been visible for 2 weeks by people without telescopes or binoculars, but it continued fading after it disappeared from our view.

Last edited by nearwildheaven; 01-01-2020 at 07:37 PM.
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Old 01-01-2020, 09:47 PM
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It's apparently at the bottom of the historic range, with a +1.294 reading on the 20th. Meanwhile Sky and Telescope's Bob King writes that to him it seemed it may be approaching +1.5 at the end of December, down from 0.5 as late as October.
I should go out tonight and have a look...no, not this time of year around these parts.

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Old 01-03-2020, 07:01 PM
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Maybe this is a sign of the Great Collapsing Hrung Disaster of Gal./Sid./Year 03758?
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Old 01-03-2020, 08:32 PM
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Maybe this is a sign of the Great Collapsing Hrung Disaster of Gal./Sid./Year 03758?
Interestingly, my father/uncle was the only man on the entire planet to survive the Great Collapsing Hrung disaster, by an extraordinary coincidence that he was never able satisfactorily to explain.
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Old Yesterday, 12:59 PM
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In case anyone wants to see a before-and-after comparison, here are two photos, one from last night and the other from just over a year ago.

The image sets were taken under different conditions and with different lenses, so disregard the differences in overall brightness and focus on the comparative brightness of stars within each photo. The December 2018 image was made edit a faster lens.

December 2018

January 2020



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Old Yesterday, 08:23 PM
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Thanks. I can't even find it in the second picture.
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Old Yesterday, 10:03 PM
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Thanks. I can't even find it in the second picture.
In the second shot the entire field is tilted about a quarter turn counterclockwise in comparison to the first photo. Rigel, the one particularly bright star, is near the right margin towards the bottom.

Betelgeuse is near the left margin towards the top. The red color is prominent as ever, but the star appears in this image only about bright as the three belt stars.

To get a better image. I should go out again tonight and use my 50mm lens as I did for the 2018 shot, but--Oregon. I was lucky to have one clear night yesterday.

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Old Yesterday, 10:56 PM
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Now I want to watch the last two minutes of "Forbidden Planet" again... just to watch the Krell planet explode...
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