I have to ask – how can we tell which way the star’s poles are oriented?
Reading through the Wiki article I found this:
No one asked, but I’d like to point out thatr Betelgeuse is an irregular variable star, as was first officially discovered by astronomer John Herschel – twice. (He noticed this while in South Africa mapping the Southern Hemisphere of the sky. When he got back to England he went over his notes and noticed that Betelgeuse was varying in intensity – he forgot that he had discovered this earlier) Nevertheless, the Encyclopedia Britannica has been reporting for years that it isn’t. This would come as some surprise to the folks at the American Asociation of Variable Stars, who have a century-long database on the star’s intensity.
About a dozen years agho someone took that data and submitted it to Fourier analysis, and found that Betegeuse doesn’t have a single period of variability – it has six well-defined sharp peaks in its Fourier spectrum. As far as I know, no one has ever come up with a theoretical explanation for this, but it explains why the variability of Betegeuse has been undiscovered for so long, and doubted when it was suggested – there isn’t a single, well-defined period as there is for most other variable stars.
Is Betelgeuse’s variability thought to be due to its burning helium or higher Z- materials, or is it thought to be due to it just being so bloomin’ big? (We can rule out the presence of an orbiting companion black/brown dwarf star or stellar remnant, can’t we?) Do other uber-giant stars like VV Cephei A, VY Canis Majoris also show large variability?
I thought this older discussion of supernova radiation flux and its potential dangers to Earth, might be of interest. I couldn’t tell from the discussion whether a Type II supernova explosion ~200 (+/- 45) pc away, would still have enough X-ray or gamma ray flux to harm LEO astronauts or not. I’m guessing no. Then there are the charged particles from the explosion, which my link barely touches upon.
Really stupid physics question that I’m embarrassed not to know off the top of my head: does Earth’s magnetosphere significantly deflect either X or gamma rays, or is the lion’s share of shielding done by the atmosphere?
Betelgeuse is so variable that it is called Alpha Orionis (“brightest star in Orion”) even though Rigel (“Beta Orionis”) is brighter. Perhaps Betelgeuse was brighter four centuries ago when the alpha/beta labeling was applied.
One reason there has been recent talk of Betelgeuse going supernova is that its diameter apparently shrunk by 15% over just the past 15 years, a whopping 37% reduction in volume. Is that just part of an oscillation that will go on for many thousands of further cycles, or is the core beginning its final collapse? Astronomers are unsure … but we all might find out soon! 
Is Canopus (a yellow supergiant?) indeed likely to go supernova soon? Perhaps the life cycles of stars are not well enough understood to say. (I was surprised to read at Wikipedia that, due to the speed of stars’ relative travel, Canopus had an apparent magnitude greater than Sirius a mere 90,000 years ago.)
Only charged particles are deflected by the magnetosphere. X and Gamma rays are changeless.
Betegeuse has been significantly brighter than Rigel at times during the past 200 years – you don’t have to go back a long time. It only had to be brighter at the moment Bayer was compiling his lists for it to show up this way.
And chargeless, even more to the point. 
I concur with those who think that a Betelgeuse supernova would be really cool but also a pity, what with liking [symbol]a[/symbol] Orionis the way it is. On the gripping hand, another “Crab Nebula” object on Orion’s shoulder would be cool in its way too. 
Hmm…don’t supernovae tend to produce nebulae? So, maybe Orion just got cold and put a cloak over that shoulder.
Yuh know… there’s an opportunity knocking here.
If Betelguese nova’s in the near future, and it becomes as visible as the moon in daytime, owning stock in sun screen might be a good retirement strategy! And those UV blocking sunglasses!
You can also determine the inclination of a star’s rotation by measuring the Doppler broadening of its spectral lines. If a star has its pole pointed right at us, then no portion of the star’s surface is approaching or receding, so you’ll get no Doppler broadening. Any other angle, and you will.
There have also been changes in Betelgeuse’s brightness that are attributable to starspots rotating across its surface, which you also wouldn’t see if its pole were pointing towards us. The period of rotation might be one of the variability periods CalMeacham referred to, and its dynamo period (analogous to the Sun’s 11-year cycle) might be another (I don’t know what the actual periods are, so this is just brainstorming).
I understand it will go supernova when the moon is in the seventh house, and Jupiter aligns with Mars; then peace will guide the planets and love will steer the stars.
So should I go out and buy some aquariums?
Has there been any time in recorded history when a star that had previously been a visible component of a constellation went supernova? I assume not, since the writeup that pravnik linked to in post#10 above doesn’t at any point refer to the star “RecognizableStarName” or the star “Gamma ConstellationName” etc going supernova. Just a new star when none had been seen before.
Nard to tell. The Carb Nebula is the result of an observed supernova from 1054 AD. Perhaps the stsar had previously been seen, but I’m not familiar with anyone who’s tried tyo identify the star. There were many recorded stars prior to this – look at Ptolemy’s catalog, for instance – but not all visible stars were recorded in them.
Similarly, some people have claimed that one of the Pleiades “disappeared” between the earliest times and later classical times, but I don’t know of an associated supernova, and the case is pretty iffy.
People seem to be saying that Beetlegeuse might go supernova in the future. Isn’t it mote correct to say that it might have already gone supernova?
Just don’t say the name 3 times in a row. 
If that explosion is undetectable via any means until some point in the future, it may as well have not exploded yet.
A good question that I’d also like to see answered.
Also, if it has actually supernovad (yeah, I make up my own verbs), the Hubble space telescope would be the first to see it, right? So what would be the “lag time” before it was visible to naked eyes on earth? Split-seconds, seconds, minutes…?
I’m WAGing less than a second, but what do I know?
*Way *less than a second - Hubble’s only 350 miles up and that’s about 0.002 light-seconds.
That’s not so bad, but you shouldn’t say “Candlejack” even onc