Why is Betelgeuse glowing so brightly and behaving so strangely? | Hacker News Reader

Why is Betelgeuse glowing so brightly and behaving so strangely?

theguardian.com

78 pointsbelter75 comments

When it explodes, Betelgeuse is expected to be brighter than the full moon. Gamma ray bursts appear to follow the axis of rotation of the star, and since that axis does not point directly at Earth (it is off by about 20 degrees), that's not a threat. So it will be exciting, scary and safe - like a rollercoaster that everyone on Earth gets to ride at the same time.

If it does I hope people will look to the stars more and reflect on their beautiful place in the universe. I can hardly envision a more navel gazing species than humans, and we need more people with telescopes and wide views.

Do any other species even have navels?

A few, yes: https://en.wikipedia.org/wiki/Placentalia

https://en.m.wikipedia.org/wiki/Orange_(fruit)#Navel

Chickens have belly buttons. I think anything that comes from an egg potentially has one.

Not all humans have belly buttons:

> If you ever find yourself in die company of a fundamentalist, much pleasant argumentation can result if you ask him or her a simple question: Did Adam and Eve have bellybuttons?

> For those who believe the Bible to be historically accurate, this is not a trivial question. If Adam and Eve did not have navels, then they were not perfect human beings. On die other hand, if they had navels, then the navels would imply a birth they never experienced.

https://cdn.centerforinquiry.org/wp-content/uploads/sites/29...

> But our first parents, Adam and Eve, didn't develop that way. I believe that God would not have planted on them a false indication that they had developed in a mother's womb.

https://AnswersInGenesis.org/adam-and-eve/did-adam-have-a-be...

Ah. About that "gamma bursts appear to follow the spin axis" rule - do Earth's astronomers have good data, with a comfortable n, to justify confidence that their little planet can't possibly get toasted by this rather large and unstable stellar neighbor?

Asking for a friend.

Turns out they are wrong, what are you gonna do about it? "Betelgeuse... no... stop..."

Prosecute the astronomers for inaccuracy in their warnings.

"Italian scientists convicted for not warning about deadly 2009 quake"

https://www.cbsnews.com/news/italian-scientists-convicted-fo...

How did that turn out? Were they acquitted? I've noticed in other cases that Italian prosecutors seem have an unusual amount of latitude, or is that normal?

Depends who you know in some places.

Yes, acquitted: https://www.science.org/content/article/why-italian-earthqua...

>> "Betelgeuse... no... stop..."

I have a new saying!

Asking for 6 billion friends.

How would this affect satellites?

If they are in orbit around a body orbiting Betelgeuse, I'm guessing they won't fair too well at all

I'd really love to see major space event like Beetlegeuse blowing up during my insignificant life-span

Do we have models that say what it would look like before an imminent explosion?

As in "just before it pops, the undulations are {such-and-such} for 1 month"

We will certainly have it after proper observation of at least one supernova event of each possible supernova type.

Just take a vacation to Mexico City right now.

Be careful about prioritizing yourself over the locals... [1]

[1] https://sites.uni.edu/morgans/astro/course/TheStar.pdf

> Betelgeuse is expected to explode some time in the next 10,000 to 100,000 years.

I'll settle for staying alive for 10000 years. Bring on the blood-boys!

I don't think any natural law would be broken if it goes off 10-100,000 years before "schedule". It's 10M years old after all, nobody would mind if it happens sooner :)

Have you tried saying its name three times?

It's name, it's name, it's name

Were you around in 1994? I was amazed that Shoemaker-Levy 9 happened in my lifetime.

https://en.wikipedia.org/wiki/Comet_Shoemaker%E2%80%93Levy_9

This one and Hale-Bopp really skewed my expectations of astronomy to think that these kinds of events were regular.

I was little kid back then but clearly remember when it struck Jupiter. Incredible thing

>There are records from ancient Egypt of what appears to be a star exploding as a supernova. The Egyptians described the appearance of a “second sun” in the sky, says Webb.

That statement interests me, I did a search and the closest thing I found was SN 1006:

https://en.wikipedia.org/wiki/SN_1006

But that did not come close to the brightness of the Sun and it happened a bit over 1000 years ago. To me, ancient Egypt refers to well over 2000 years ago.

So wondering if that statement is really true.

Maybe a comet?

Are you looking back far enough? Ancient Egypt really fucking ancient. Like it was about as ancient to classical antiquity as classical antiquity is to us now.

This is always a startling fact about timelines.

My favorite fact about timescales is that Cleopatra lived closer to the moon landings than to the building of pyramids.

What!?

The pyramids at Giza are really, really old.

Cleopatra was part of the Macedonian/Greek dynasty in Egypt, which comes basically at the tail end of what one might consider "ancient Egypt". The time span we lump together as "ancient Egypt" (specifically, dynastic ancient Egypt—"pre-dynastic" stretches back many centuries before that) is so long that stuff from the first third or so of it is farther, time-wise, from Cleopatra than the moon landings were.

Wikipedia:

> All [the three big pyramids at Giza] were built during the Fourth Dynasty of the Old Kingdom of ancient Egypt, between 2600 and 2500 BC.

Cleopatra is tied up with Julius Caesar and Antony (as in Shakespeare's Antony and Cleopatra) and all that happens just before the BC/AD transition, and these numbers are large and fuzzy enough we can just call her time 0. ~2500 years after the pyramids, ~1970 before the moon landings. Plus or minus a few years, but it doesn't make much difference.

I remember visiting Lincoln Cathedral and realising that when it was built in 1311 it was the first new tallest building for 3900 years... (160m as opposed to the 147m of the great pyramid) though the spire collapsed 238 years later.

The one that always gets me is that there were still living mammoths (on Wrangel Island in the Arctic) when the Great Pyramid was built. [1]

1.https://en.wikipedia.org/wiki/Wrangel_Island#First_human_set...

Here's another good one: the tyrannosaurus rex lived closer in time to you than it did to the stegosaurus.

I wondered too what Webb was referring to, and didn't find a hint of it either.

"The known history of supernova observation goes back to 1006 CE. All earlier proposals for supernova observations are speculations with many alternatives. " -- https://en.wikipedia.org/wiki/History_of_supernova_observati...

There's a rock drawing in Kashmir, India of what might be a supernova (HB9) dating to -4600BCE ...

https://www.theguardian.com/world/2018/jan/10/two-suns-no-it...

"The Great Dimming of Betelgeuse: a Surface Mass Ejection (SME) and its Consequences" (2022) - https://arxiv.org/abs/2208.01676

From this paper : "Spectroscopic evidence for a large spot on the dimming Betelgeuse" - https://arxiv.org/pdf/2108.03472.pdf

"Evidence for a large cool spot: What could lead to a temperature drop by 170 K? It should be noted that the lowest temperature obtained on 31-01-2020, Teff = 3476 K, would be one of the coolest effective temperatures measured for a Galactic RSG... According to the stellar evolution theory, the Hayashi limit (the lower limit of Teff for stars in hydrostatic equilibrium) for a star like Betelgeuse is ∼3500 K (see, e.g., Figure 6.5 in 16). Nevertheless, the significance of the Hayashi limit for RSGs is still open to debate. It has been suggested that the stars moved to the forbidden region of the Hertzsprung-Russell (H-R) diagram are not able to maintain their hydrostatic equilibrium and this may actually drive episodes of enhanced mass loss."

It seems could have broken the Hayashi limit that describes a star's lowest possible surface temperature at a given mass or radius for Red Super Giants.

In those cases it seems either:

- Would go Supernova

- Would have mass loss that would cause the star to shrink back within the Hayashi limit. So no Supernova for you...

But do we know if the amount of temperature drop is reasonable enough for a mass loss, or it's too great and automatically implies supernova?

I don't think anybody knows, but I am sure there is a Nobel prize at the end of that answer. In the meanwhile...

See "25.1 Main characteristics of massive star evolution" on this one: "Understanding Stellar Evolution" - https://www.hennylamers.nl/wp/wp-content/uploads/2014/10/Lam...

"Hayashi limit" - https://en.wikipedia.org/wiki/Hayashi_limit

tl;dr

Betelgeuse, the closest red giant star to Earth, is exhibiting unusual behavior. Normally, the star cycles between bright and dim states every 400 days. However, between late 2019 and early 2020, it went through a "great dimming" due to a dust cloud that obscured our view of the star. Currently, Betelgeuse is glowing at 150% of its normal brightness and is cycling between bright and dim states every 200 days, which is twice as fast as usual, making it the seventh brightest star in the night sky.

The great dimming was caused by a surface mass ejection of gas and dust, a phenomenon resulting from an anomalously hot convective plume. This ejection, which was several times the mass of Earth's moon, has caused changes in the star's forces and stability.

“If we were to throw one of our arms away from us, it changes the way our forces move in our body. And a similar thing happened with poor Betelguese,” says Webb.

Betelgeuse is anticipated to explode as a supernova in the next 10,000 to 100,000 years.

"Is Earth in danger if Betelgeuse goes supernova?" - https://www.skyatnightmagazine.com/space-science/earth-dange...

I hate articles filled with meandering fluff. The answer is buried 3/4 of the way down the page, and it's "No, it's too far away".

When headlines end with a '?' the answer is: No

> Betelgeuse is anticipated to explode as a supernova in the next 10,000 to 100,000 years.

I would like Theguardian to expose a standard deviation for this kind of data (because I have read from other sources that nobody has the data, it easily may be tomorrow).

The article states that we don't know, a scientist is quoted saying that it could have already happened for all we know.

642.5 light years is a pretty sizable lag time, in human terms.

> it easily may be tomorrow

Tomorrow is in the next 10,000 to 100,000 years.

> Betelgeuse is anticipated to explode as a supernova in the next 10,000 to 100,000 years.

Too long. Speed it up.

Let's put all this cancer research on hold and figure out a way to accelerate heavy metal burning in stellar cores!

No different than spending money on the military to accelerate heavy arms ordinance manufacturing instead of hospitals and schools.

All current human activity combined will have less impact on when the star explodes than a single snarky comment has on heavy ordinance manufacturing.

Space is big.

http://www.wolframalpha.com/input/?i=size%20Betelgeuse%2Fsiz...

The idea that stars change in state on single-causes from features on their completely chaotic magnetosphere is quite frightening.

> which was several times the mass of Earth's moon

It strains intuition that this would even be observable, it's such a tiny fraction of the total mass of the star.

Just to get things back into proportion, Betelgeuse is one of several hundred pulsating red supergiants visible with the unaided eye, binoculars or a small telescope (here are some around the Double Cluster in Perseus: https://www.dritter.net/astronomy/clusters/ngc869-884_03.asp...). Many of these are significantly more luminous than Betelgeuse, and it is far more probable (just from the numbers) that one or more of these will turn supernova before Betelgeuse does. The recent fade and subsequent brightening of Betelgeuse are fairly typical behaviour for pulsating red supergiants, and are probably not relevant to whether it is about to turn supernova or not.

Probably it's got something to do with the Great Collapsing Hrung Disaster

But what's a Hrung and why would it choose to collapse on Betelgeuse?

Wait a minute. If you emit material wouldn't you spin slower. Take the arm waving example from the article.

Stand in the middle of the room and spin with you arms at your side. Now suddenly spread you arms. You will notice a marked reduction in rotation speed, not an increase.

Who can explain this for me?

Imagine instead that you’re sitting on a swivel chair and you fire a gun with your right hand. This is more akin to how ejection of materials work. When you put your hands out on the swivel chair, the hands are still attached and are forced into orbit around your torso, when you eject material this isn’t the case, and it leaves the system.

In that example, your arms are still rotating about an axis. The moment of inertia of the rotating body increases, so the angular velocity decreases. Imagine instead that the ejected material is no longer rotating about an axis (say, you detached your arms and flung them away in a straight line); the moment of inertia of the remaining rotating body _decreases_, so the angular velocity increases.

This doesn't (necessarily) have anything to do with rotation speed, and the article doesn't say it does. The fact that Betelgeuse is pulsating more quickly does not imply that it is rotating more quickly.

Making an entire star suddenly spin twice as fast on its axis would require a staggeringly, absurdly huge transfer of energy and angular momentum. The mass ejected from Betelgeuse was much, much smaller than the star's total mass, and would not have been capable of causing such an effect.

Your arms are still attached, unlike ejected mass.

Imagine a figure skating spinning fast. Then holds out her arms and slows down. Then someone chops her arms off.

Sort of like that.

I don't think the pulsations are due to rotation. It grows and shrinks periodically, causing changes in absolute magnitude; and there seems to be more than one period. The various periods seem to be related harmonically.

Betelgeuse could have exploded while Copernicus was looking at it and we still wouldn't know it already exploded.

We will know if anything happens about 642 years later.

It’s a shame we’re not taking better care of our galaxy. So many science deniers.

Title needs [1380].

Someone said its name three times?

Sorry all, that was me. It was 1989, I was in kindergarten, I didn't really know what I was doing. My bad.

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