Somebody said it three times, didn't they?
February 2, 2020 6:44 PM   Subscribe

Betelgeuse is also known as alpha Orionis because it is usually the brightest star in the constellation Orion. Right now, though, it is at its lowest recorded brightness, and getting dimmer. This is of particular interest since the difference is obvious to the naked eye, and observers familiar with the constellation of Orion will find that it looks odd indeed. Oh, and also because Betelgeuse is the closest star to Earth that might go supernova...

...though don't get excited, because, though we might see a supernova tomorrow, it might also take 100,000 years.

The variability of Betelgeuse was measured by Sir John Herschel (likely assisted by his sister Caroline Herschel) in 1836, but was known to Aboriginal Australians long before that. In a Kokatha oral tradition, once told to journalist Daisy Bates, a club-toting man named Nyeeruna (Orion) pursues the Yagarilya sisters (the Pleiades), and is taunted by Kambugudha (the Hyades), who lifts her left foot (Aldebaran) and kicks dust at Nyeeruna, dimming his fire magic. As Nyeeruna's magic recovers (Betelgeuse regains its brightness), Kambugudha and an array of creatures to fight him and the star dims again.

Betelguese is a red supergiant about 650 lightyears away. It is currently classified as a semi-regular variable (type SRc), with an apparent magnitude that varies between approximately 0.2 and 1.2 as the star's outer envelope heats and expands, then cools and shrinks, over the course of several years. Its current magnitude is dimmer than 1.5th magnitude. (Magnitudes are measured "backwards." A dimmer star has a higher magnitude.)

The current dimming is probably just due to a chance alignment of several cycles within the star, not an incipient supernova explosion, but nonetheless amateur and professional astronomers around the world, including the American Association of Variable Star Observers, are keeping a close eye on it. If Betelgeuse does go supernova, it will be the first supernova observed in our own Milky Way Galaxy since 1604.

Betelgeuse previously.
posted by BrashTech (40 comments total) 36 users marked this as a favorite
 
If you say Betelgeuse three times, Candyman will appear.
posted by dances_with_sneetches at 7:12 PM on February 2 [2 favorites]


Antares is a bit closer (550 ly), and is also deep into its late stages, and could also go supernova just about any time, astronomically speaking.
posted by tclark at 7:14 PM on February 2 [2 favorites]


Should we report this to Starfleet?
posted by RobotVoodooPower at 7:18 PM on February 2 [11 favorites]


I thought Betelgeuse was still hanging out in the waiting room with his shrunken head
posted by Ber at 7:20 PM on February 2 [3 favorites]


That's funny, I was just now outside looking at the stars with the kids, and I pointed out Betelgeuse to them and did the whole "back when I was young, that there star was the brightest in Orion".
posted by Maxwell's demon at 7:23 PM on February 2 [7 favorites]


What do you say three times to make Michael Keaton disappear?
posted by oneswellfoop at 7:39 PM on February 2


Should we report this to Starfleet?

Don't bother, they still won't save the Romulans.
posted by Halloween Jack at 7:40 PM on February 2 [12 favorites]


If Betelgeuse where to asplode tomorrow, then it will actually have asplodified sometime around the time of the Christopher Columbus disaster.
posted by drivingmenuts at 7:42 PM on February 2 [5 favorites]


From the recent entry, This Early Warning Signal Could Successfully Predict Betelgeuse's Supernova at the Starts with a Bang physics and astronomy blog:

When your supergiant star begins fusing carbon, that stage takes on the order of 100,000 years to burn to completion, the overwhelming majority of the time a star spends in the supergiant phase.

Neon burning takes only a few years at most; oxygen burning typically takes merely months; silicon burning endures for only a day or two at most. These last stages do not result in any significant temperature changes or photosphere changes that are observable in a meaningful way.

If we want to know what's going on in the core of a star — our only true indicator of when a supernova is coming — observing the electromagnetic properties of the star won't give it to us; there is no change in a star's temperature, brightness, or spectrum that occurs after the transition from carbon-burning to heavier elements.

But the neutrinos tell a vastly different story.
posted by jjj606 at 8:09 PM on February 2 [13 favorites]


Surely someone is looking at the star's spectrum to look at what it is burning? (or rather surely it spectrum changes as new elements show up)
posted by mbo at 8:42 PM on February 2 [1 favorite]


What it is burning in its core isn’t necessarily what it burns at all layers; so if the outer layer is still burning hydrogen, then many of the photons from the inner layers will not get out directly (they will hit stuff in the outer layer instead) meaning the spectrum visible from outside isn’t that much different. (I got this from reading the article jjj606 posted).

But neutrinos hit things less, so neutrinos from burning heavier elements do come out with higher energy, and that produces an effect we can see with modern neutrino detectors. Well, that we should be able to see anyhow.
posted by nat at 9:21 PM on February 2 [2 favorites]


I don't know what's going on with Betelgeuse, but I feel confident that the biggest celestial event of the year is not going to happen in 100K years.
posted by aubilenon at 9:48 PM on February 2 [3 favorites]


might go supernova...

Not another corona to worry about?!?
posted by fairmettle at 10:18 PM on February 2 [1 favorite]


The general consensus from astronomers I follow is that if Betelgeuse started to brighten again by the start of February it was probably just a conjunction of dimming cycles previously unknown to us (unusual but possible, since we only have data for the star for the last two centuries), or some other phenomena (probably a massive amount of dust). But if it continues, as it has, then something else is going on. Right now, Betelgeuse's luminosity is down by 60% from its usual brightness, and its radius has expanded by 9%. That's a lot of loss in a very short time for a very large star.

I generated a light curve for Betelgeuse (aka Alpha Orionis / Alf Ori, the Bayer classification for the star), and I'll be keeping an eye on it.

BrashTech, thanks for including a perspective on the star from native peoples: it's very much appreciated.
posted by Bora Horza Gobuchul at 11:24 PM on February 2 [17 favorites]


The Great Collapsing Hrung Disaster of Gal./Sid./Year 03758 which wiped out all the old Praxibetel communities on Betelgeuse VII is shrouded in deep mystery; in fact, no one ever knew what a Hrung was nor why it had chosen to collapse on Betelgeuse VII particularly.
posted by Just this guy, y'know at 2:09 AM on February 3 [15 favorites]


Something that doesn’t even surprise me anymore: someone answers a question on metafilter right before it is asked.
posted by sjswitzer at 2:37 AM on February 3 [1 favorite]


It’s all the hot tachyons flying about.
posted by curious nu at 5:14 AM on February 3


an effect we can see with modern neutrino detectors

What's the state of the art of neutrino astronomy today? A quick read on Wikipedia suggests we're still very excited to detect single neutrinos; the big IceCube project detected its first emission from a distant stellar object last year. Is there any realistic chance of us capturing a neutrino from Betelgeuse? 650 ly is so very close, but I can't puzzle out how much that helps. Surely stars are emitting neutrinos all the time; is there something special about a star at Betelgeuse's stage that means we may have an easier time detecting neutrinos from it? I guess at the moment of supernova it'll suddenly get very busy, but before then?

I don't mean to diminish the science.. I think it's amazing we can detect things like neutrinos at all, and love that humanity is willing to spend $$BB and the efforts of thousands of scientists to build a detector that may get 1, 5 signals a year. Just trying to understand what the limits of our observation capabilities are.
posted by Nelson at 6:31 AM on February 3


All your questions are discussed in detail in jjj606's link: This Early Warning Signal Could Successfully Predict Betelgeuse's Supernova.
posted by ryanrs at 6:53 AM on February 3 [2 favorites]


Should we report this to Starfleet?

Not really in their wheelhouse. You might have better luck over at Dark Star.
posted by flabdablet at 7:33 AM on February 3 [3 favorites]


Thanks ryanrs; I had quit reading before I got to the good part
a tank that contained 1,000 tons of water should see approximately 32 events per day from a late-stage silicon-burning star located at the distance of Betelgeuse
The key thing here is the silicon-burning stage happens just a few hours before the actual supernova collapse, and while it's nowhere as energetic as the supernova itself it should be detectable and give us a few hours' advance warning. Current neutrino detectors are bigger than that 1000 tons; the article says our current detectors should see a few thousand neutrino events just before the supernova. Plenty of time to get to the shelters!
posted by Nelson at 7:39 AM on February 3


Plenty of time to get to the shelters

"And then Betelgeuse went supernova and vapourized the planet" is such a lazy way for a writers' room to resolve all the conflicts they built into their Presidency.

might be something from the stars in two weeks, they're doing very well, we'll have to see what happens
posted by flabdablet at 7:44 AM on February 3 [6 favorites]


When Betelgeuse does go supernova, how large of an area will it affect? Obviously, now is not a good time to be orbiting the star, but is there a radius in, say, light years that will be within the immediate blast zone?

Also, what will we observe here, on a scale of “Blink and you’ll miss it” to “It looks like a second sun”?
posted by Big Al 8000 at 8:14 AM on February 3


[janet] Not an astronomer. [/janet]

But the stuff I've seen astronomers do points at 50 or so light years as being minimum safe distance to enjoy a supernova like Betelgeuse would generate.* At a few light years away, the radiation pulse from the supernova would be enough to directly kill lots of stuff and zap the ozone layer, indirectly killing lots more stuff.

When it goes, we're expected to have something visible in daylight and in the same ballpark of brightness as a full moon.

*There are other kinds of collapse events where the minimum safe distance is *much* farther. IIRC and I might not, a gamma-ray burster pointed at Earth pretty much anywhere in the galaxy would be a Bad Day.
posted by GCU Sweet and Full of Grace at 8:45 AM on February 3 [3 favorites]


> When Betelgeuse does go supernova, how large of an area will it affect? Obviously, now is not a good time to be orbiting the star, but is there a radius in, say, light years that will be within the immediate blast zone?

It depends on what you are - planets are pretty robust and even the ones in high enough orbit around Betelgeuse will likely be singed and ejected but still remain planets. I wouldn't want to be a living thing anywhere within the nearest handful of parsecs though.

> Also, what will we observe here, on a scale of “Blink and you’ll miss it” to “It looks like a second sun”?

A supernova at that distance will be extremely bright, possibly even brighter than the full moon and likely visible at some times during the day. Though it does not threaten life as we know it here.

And I seriously doubt it's going boom (and will be delighted to be proved wrong!) - though giant stars burn through their fuel quickly, that's in astronomical time. It's probably having a bad month.
posted by BigCalm at 8:53 AM on February 3


This Ask xkcd is about lethal neutrino fluxes:

If you observed a supernova from 1 AU away—and you somehow avoided being being incinerated, vaporized, and converted to some type of exotic plasma—even the flood of ghostly neutrinos would be dense enough to kill you.

No matter how bad you think a supernova is, it's actually worse.
posted by thatwhichfalls at 9:00 AM on February 3 [3 favorites]


When it does eventually go supernova, it's going to be right after some asshole looked up at the night sky and said "give me a sign!" And when that happens, that asshole is going to be insufferable.
posted by Weeping_angel at 9:04 AM on February 3 [8 favorites]


sjswitzer: Something that doesn’t even surprise me anymore: someone answers a question on metafilter right before it is asked.

What is a tachyon?
posted by fader at 9:51 AM on February 3 [7 favorites]


In 1987, there was a supernova (SN1987a), and even with significantly smaller/less sophisticated neutrino detectors, humans were still able to detect an excess of neutrinos from it (something like 30 neutrinos). And that one was 168000 light years away. I'm not an astronomer, just a physicist, but the name 1987a is still spoken about frequently enough that I have it memorized.

So yes, Betelguese going would be An Event in the neutrino world.
posted by nat at 9:52 AM on February 3 [3 favorites]


In 1987, there was a supernova (SN1987a)

An age ago I read a book about this and the author calculated that, given the total volume of human vitreous humor on the Earth at the time, a single neutrino collision should have happened in a human eye. Since retinal cells are responsive to even single photons, that means that, statistically, someone saw a flash of light when the supernova wave front hit the Earth. Assuming they weren't asleep.
posted by thatwhichfalls at 10:01 AM on February 3 [6 favorites]


The Betelgeuse supernova will be close enough that you definitely won't miss the show, but not so close that you'll get the day off work.
posted by ryanrs at 10:17 AM on February 3 [3 favorites]


> I'm not an astronomer, just a physicist, but the name 1987a is still spoken about frequently enough that I have it memorized.

Yes, it was quite an event. Apocryphal story, but the first 7 neutrinos from SN1987A led to 7 theses written up...

Since Galileo's invention of the telescope, astronomers haven't had a supernova in our Milky Way to stare at. The closest we've had in SN1987A in the Large Magellanic Cloud, which is a satellite galaxy separate from the Milky Way. It's frustrating.
posted by RedOrGreen at 11:23 AM on February 3 [1 favorite]


But if you asked me to place a bet, I'd bet on Eta Carina before Betelgeuse.
posted by RedOrGreen at 11:25 AM on February 3


and love that humanity is willing to spend $$BB and the efforts of thousands of scientists to build a detector that may get 1, 5 signals a year.

They also have the really clever side effect of being able to detect every nuclear powered item on earth (reactors, centrifuges, weapons tests, etc) in real time, all the time, through the earth itself like it were invisible.. So that might be a clue as to where some of the funding is coming from.

What it is burning in its core isn’t necessarily what it burns at all layers; so if the outer layer is still burning hydrogen, then many of the photons from the inner layers will not get out directly (they will hit stuff in the outer layer instead) meaning the spectrum visible from outside isn’t that much different.

The only place a star 'burns" (engages in fusion of lighter elements into heavier ones) is in the inner core. (IIRC, It is believed to be kept separate by the intense magnetic dynamo that drives the magnetic field of the sun) So, even if a star runs out of fuel in the core, the outer layers are all still 75% hydrogen 24% helium (and ~1% everything else) like it started out with in the beginning. There will be some changes to the chemical composition over time (usu increases in C,N,O, and metallic elements) and while these are easyish to detect and vital to our understanding and classification of stars, it really amounts to only a tiny % of a stars makeup...like a change of at most a few% of mass during the lifetime of the star.
posted by sexyrobot at 12:22 PM on February 3 [1 favorite]


And speaking of the Antarctic neutrino observatory, and probably unrelated, a new kind of neutrino has been detected.
posted by blue shadows at 12:50 PM on February 3


Wait, how would a neutrino detector detect a centrifuge?
posted by ryanrs at 3:52 PM on February 3


The only place a star 'burns"

His name is Alex!
posted by MrBadExample at 5:59 PM on February 3 [5 favorites]


They also have the really clever side effect of being able to detect every nuclear powered item on earth (reactors, centrifuges, weapons tests, etc) in real time, all the time, through the earth itself like it were invisible.. So that might be a clue as to where some of the funding is coming from.

None of the funding for fundamental-physics-grade neutrino detectors is coming from the sources you have in mind. Unfortunately.

However, smaller neutrino detectors that you can put right outside a nuclear reactor building and measure the neutrino spectrum to find out what the history and composition of the current fuel is (and hence suss out whether certain substances have been extracted for potentially-nefarious purposes) have been proposed and I believe initial testing of the idea has already begun.

1/r^2 is a harsh mistress.
posted by heatherlogan at 6:26 PM on February 3 [1 favorite]


Does anyone know of any bookmakers who take bets on this kind of stuff, or even just calculate odds? I'd love to see the odds for a Betelgeuse supernova in 2020, and similar. The "weirdest" odds i can find are for TV shows though
posted by Chaffinch at 2:51 AM on February 4


Also, what will we observe here, on a scale of “Blink and you’ll miss it” to “It looks like a second sun”?

This article (in Forbes of all places) was referenced in some of the astronomy groups I follow and seems to have a lot of good info. Tldr: the estimated visible effect would be significant brightening over 10 days or so, followed by a plateau lasting a few months, then a gradual dimming over the course of a year or two. So there'd be plenty of time to see it. Max brightness wouldn't be a second sun, think more like Venus but way brighter - likely bright enough to see during the day. I think the odds are low any of us will live to see it, but man I'd love to be proved wrong.

Note - I'm not a professional, I just like to stargaze and read way too much about it.
posted by photo guy at 5:04 PM on February 4 [1 favorite]


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