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Why is Betelgeuse glowing so brightly and behaving so strangely?

theguardian.com

11–20 of 81 posts

Re: Why is Betelgeuse glowing so brightly and behaving so strangely?

#11
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?

Re: Why is Betelgeuse glowing so brightly and behaving so strangely?

#12

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.

Re: Why is Betelgeuse glowing so brightly and behaving so strangely?

#13

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?

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.

Re: Why is Betelgeuse glowing so brightly and behaving so strangely?

#14

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?

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.

Re: Why is Betelgeuse glowing so brightly and behaving so strangely?

#16

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?

Your arms are still attached, unlike ejected mass.

Re: Why is Betelgeuse glowing so brightly and behaving so strangely?

#18
post #7

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.

Re: Why is Betelgeuse glowing so brightly and behaving so strangely?

#19
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...

Re: Why is Betelgeuse glowing so brightly and behaving so strangely?

#20

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, w…

> 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).

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