quote:Well, you see, Betelgeuse has been shrinking continuously since 1993, at an increasing rate. By June 2009, it had shrunk 15% from its size as measured in 1993.
But wait! There's more. It is rumored, though I have been unable to find any reliable confirmation of the source (which is claimed to be first-hand) that the latest observations from Mauna Kea show that Betelgeuse is now shrinking so fast it is no longer round. (Due to conservation of angular momentum, when a massive star collapses gravitationally, it collapses faster at the poles, becoming increasingly oblate — flattened — as its final collapse accelerates.)
What does this mean?
Well, briefly, what it means — if true — is that Betelgeuse could be within as little as weeks of a Type II (core collapse) supernova. (Astronomers have considered for some time that Betelgeuse has the potential to go supernova any time in the next thousand years or so. "Any time" may just turn out to be rather sooner than expected.)
Sure it's a slim chance, but if it does happen, it would be awesome. Just wanted to give you all heads up of awesome of this potential magnitude. Posts: 1711 | Registered: Jun 2004
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Man, if Betelgeuse blows up in my lifetime, wouldn't it create 24 hour light brighter than the moon?
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I'm not sure of the mechanics of it, but I think the chances are it has *already* gone supernova, since it's 640 light years away.
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Out of interest, just how bright would a supernova 640 light-years away be? Supernovae outshine entire galaxies; move a galaxy that close and you might find yourself a bit uncomfortable.
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KoM: I'm fairly certain that only supernovae within our galaxy or nearby galaxies outshine other, more distant galaxies. That is, at the same distance, supernovae are much less bright than galaxies.
640 light years is within the range that might have a noticeable impact on earth, I believe.
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What do you want to bet that if Betelgeuse does go supernova, there will be more than a few tragic incidents involving fringe born agains who think the rapture is upon them?
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I guess I should clarify, by "tragic incidents", I mean a few wackos who do things like jump from 10th story balconies believing they will be sucked up into heaven.
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Btw, it doesn't sound like there's any real scientific basis behind the idea that this will happen sooner rather than later. Someone even got a story onto Slashdot about how this wasn't a real bit of news.
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They might not have insurance to cover their medical care if they survive the fall, or to cover burial expenses if they don't. Then you get to pick up the tab.
Believers in imminent Apocalypse have a habit of taking their families with them, without regard toward the individual family members' feelings on the matter.
Or you might be walking under one of those balconies.
And somebody's gotta clean the splatter up, it ain't gonna be the jumper. And somebody has to investigate and confirm the cause of death. Guess who's gonna pay the tab?
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"Hi, my name is Bob, and it's my job to clean up the suicide victims after, like, the movementarians or anarcho-capitalists all drink the kool aid. Did I mention how much I loathe humanity?"
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quote:Originally posted by fugu13: KoM: I'm fairly certain that only supernovae within our galaxy or nearby galaxies outshine other, more distant galaxies. That is, at the same distance, supernovae are much less bright than galaxies.
I am quite certain that this is not true, for the following reason: Today I attended a seminar where the subject was recent observations of supernovae in a particular patch of sky. The speaker showed pictures where, and I quote, "The bright central patch is the supernova and the weak fuzzy blob is the host galaxy." In other words, the supernovae were outshining the galaxy they were found in, which by construction is at the same distance.
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Actually there is, fugu13. The diameter of Betelgeuse has decreased by ~15% while the light output and the spectrum has remained essentially the same.
That means the new surface which has only ~72% of the old surface area is putting out as much energy, while the energy levels of photons making up the spectrum are failing to make the corresponding increase in frequency. ie Some truly weird physics is going on.
The new volume which is only ~61% of the old volume is undergoing severe compression and experiencing severe pressure increases. So the bounce is gonna be equally severe. If the bounce is severe enough, supernova. If it's not, the light output should increase greatly as the bounce expands outward.
Once bouncing begins, the time between bounces decreases. Ever less energy is available in the elements used in the consecutive fusion reactions, so there's ever less fuel to prop up the star's volume.
So irrespective of whether Betelgeuse goes supernova on this particular bounce, it probably is far closer to going supernova.
About the only saving grace lies in the probably. We really don't have sufficient experience in observing supernovae to be sure that Betelgeuse is the right kind of star to undergo the process. It's bounces could blow off enough mass each consecutive time that eventually Betelgeuse won't have enough mass to undergo the type of collapse that produces a supernova. Theoretically, we think that there will not be enough mass blown off. But observing reality has shown the contemporary most-favored-theory to be wrong before. Reality always trumps theory.
One thing we shouldn't have to worry about is radiation from a Betelgeuse supernova causing great harm to Earth. Yes it would outshine the galaxy. But most of our galaxy is far away. Try reading a paperback by starlight on a moonless night -- you'd be making the attempt by the light of our MilkyWayGalaxy and the rest of the Universe combined (excluding our Sun) -- and compare that to reading during the day. And even without the Sun or the Moon in the sky, the zodiacal light from sunlight being reflected off of planets and debris in the Solar orbital plane comprises a significant portion of that "starlight on a moonless night".
A nightlight is tiny compared to the carbon-arc spotlights used at a Hollywood premiere. Yet you are far more likely to be able to read by a nightlight nearby than by a spotlight as far away as Hollywood.
And particle radiation shouldn't be a great hazard either: both because of the inverse-square rule that limits the amount of light from distant suns that reaches us, and because Betelgeuse is not oriented in a manner that would aim the polar jets toward us.
quote:The post also talks about Betelgeuse shrinking. That claim is from observations made over the course of many years. Those data indicate the star is shrinking, but it’s unclear what they mean. While it may mean the star is in fact shrinking, starspots (sunspots on another star) may be fooling us, for example. Also, red supergiants aren’t like marbles, with a clean, sharp surface. They are balls of gas, extended and bloated, so there is no real surface. It’s therefore entirely possible the astronomers aren’t even really measuring the surface of the star at all, and it’s just the highly extended atmosphere that’s changing.
I personally would really like it if Betelgeuse DID go supernova, just 'cause it would be cool. But there's an awful lot we don't know.
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quote:Yes it would outshine the galaxy. But most of our galaxy is far away. Try reading a paperback by starlight on a moonless night -- you'd be making the attempt by the light of our MilkyWayGalaxy and the rest of the Universe combined (excluding our Sun) -- and compare that to reading during the day. And even without the Sun or the Moon in the sky, the zodiacal light from sunlight being reflected off of planets and debris in the Solar orbital plane comprises a significant portion of that "starlight on a moonless night".
This is true but not relevant. As noted above, the point is not that a supernova would be brighter in our sky than the Milky Way, this is not a very impressive trick, but that it would actually have a greater total luminosity. That is, it would shine as brightly as all those 100 billion stars. Try putting 100 billion stars 640 light-years away and you'll see something. Specifically, taking the Sun as typical and at an average distance of 8 light-minutes, you would see a star having about 5e-5 of the Sun's apparent luminosity. This would give it an apparent magnitude of -16 or so, much brighter than the full Moon and easily visible by day.
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An interesting twist of an End of the World prophecy could be that on such-and-such day, there's a catastrophic occurrence (like the supernova) but that it still takes several hundred years for the effect to ripple into Earth.
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And the Sun isn't like a "marble with a sharp surface". The photosphere -- as deep into the Sun as we can see visually -- is quite tenuous, with a density that is ~0.01% that of Earth's atmosphere at sea level.
Most of the mass is within the ~2.7% of the Sun's volume that contains the core and the nearby region which still supports some small amount of fusion. And most of the rest is contained within the remaining portion of the Radiative*Zone (surrounding the core) which (excluding the core) occupies ~33% of the Sun's volume.
The remaining outer 65+% of the Sun's volume contains the ConvectiveZone which varies in density from 1/5th that of water at the base, to the barely there density of the photosphere atop its surface. So the Sun's ConvectiveZone could also be described as "extended and bloated", though admittedly not as much as Betelgeuse's.
* That also contains the somewhat fusion-supporting region outside of the core. The core itself occupies only ~1.4% of the Sun's volume. (Which is where the arithmetic went "more than 100%" off on ya if you were adding it up)
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I certainly agree, KoM, that a Betelgeuse supernova show would quite IMPRESSIVE. Just wanted to head off the "We're all gonna fry!!!" contingent before they join in on the rumor-mongering nonsense that'll cause the less stable amongst us to leap off of tall buildings in a single bound.
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I feel bad for the Betelgusians. Although, it might encourage them to visit, which would be cool. Hope they don't plan on staying, but I guess they could have Mars.
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quote:Also, it’s been known for a long time that Betelgeuse is a variable star; its light output changes. This shrinking may just be a part of that natural cycle, and again no indication of an explosion.
Having said all that, I’ll note that someday, Betelgeuse will explode. That’s for certain! But it’s also way too far away to hurt us. A supernova has to be no farther than about 25 light years away to be able to fry us with light or anything else, and Betelgeuse is 25 times that distance (which means its power to hurt us is weakened by over 600x). It’s the wrong kind of star to explode as a gamma-ray burst, so I’m not worried about that either.
At that distance, it’ll get bright, about as bright as the full Moon. That’s pretty bright! It’ll hurt your eyes to look at it, but that’s about it. The original post says it may get as bright as the Sun, but that’s totally wrong. It won’t even get 1/100,000th that bright. Still bright, but it’s not going to cook us. Even if it were going to explode soon. Which it almost certainly isn’t.
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The original post has been updated, with a reference to a post on Bad Astronomy blog. Unfortunately, it's a rumor. Would have been a cool light show.
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sorry, missed that. I thought I updated the page before posting, but apparently you posted while I was off reading the Bad Astronomy post.
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quote:Originally posted by Glenn Arnold: Betelgeuse rises in Trinidad and Tobago at 7:07 and sets at 19:23 Universal time.
Gosh, I would hate to be in Trinidad and Tobago when that happens. I mean, a star shooting out of the ground in the middle of town is bound to cause some damage and light some fires.
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quote:Originally posted by CaySedai: sorry, missed that. I thought I updated the page before posting, but apparently you posted while I was off reading the Bad Astronomy post.
Oh it's fine! That was a "Hurrah Bad Astronomy!" rather than a "How dare you steal my link!" I could see the timestamps were close .
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I do try to be conversant with the thread before posting, but sometimes I'm slightly off the mark.
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quote:Gosh, I would hate to be in Trinidad and Tobago when that happens. I mean, a star shooting out of the ground in the middle of town is bound to cause some damage and light some fires.
So if I'd said the sun will rise tomorrow in Trinidad at 6:00 AM you'd assume that the sun rises straight up through the Earth?
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quote:Originally posted by The Rabbit: That would be so cool.
I wonder if Betelgeuse is visible from Trinidad right now?
No. Try October (late at night) through March (evening).
The sun is currently setting at 18:24 in Trinidad and twilight doesn't really exist this close the the equator, so presuming Glenn's numbers are accurate, I should be able to see Betelgeuse from Trinidad in the early evening right now.
But then, I'm heading to northern Germany for most of the summer so that will be kind of irrelevant in the off chance that Betelgeuse does supernova in the next few weeks.
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I'm having a hard time deciding if it would be cooler to see the supernova being visible in broad daylight (just because you don't usually see anything but the moon and sun during daytime) or in its full glory at night.
'Course if it can wait until fall we could see it in both day and nighttime. Someone please make an appointment with Betelgeuse for a fall supernova.
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It will be of interest to astronomers for a long time, certainly; it's rare that they get to see one at close range. But naked-eye visibility by day will only last two or three weeks.
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You being being able to see it during the day would only last that long? What about at night?
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