What is the drama going on with Betelgeuse

[spacewithnavu]

Lets know what is happening in Betelgeuse, Is the END COMING SOON? Lets see

View: https://www.youtube.com/watch?v=Tj5QAZYUUmI&t=521s

 

[Michael Varn]

My theory, among others, about Betelgeuse is that it has already gone supernova.

This might account for why it appears to be doing unusual things.

Based on what I remember about this star there is not a consensus among astronomers in terms of how far away it is compared to most other stars.

I have heard of estimates as close as 500 light years, but as far as 800 light years.

This to might be due to distortion from the shock wave. Of course we can"t see it yet.

The shockwave could arrive at anytime without warning, but the good news is it's just going to be a really neat light show.

All astronomers are sure about this. It will not effect us in anyway because it is to far away.

When this supernova reaches us, it may be hard to see in the daytime, but at night it will appear about as large and as bright as a full moon for about six months.

I sure hope it happens in our lifetime, because I would love to see it.

 

[Eva Braun]

In its normal state, Betelgeuse is about 100 thousand times brighter than the Sun, but it burns up all its hydrogen reserves, so its life is very short - only up to 10 million years. Given that the state of the red supergiant is the last stage of Betelgeuse's life, I'd take the unusual changes in the star's brightness as the first sign of its imminent death and transformation into a supernova.

 

[SpaceRaider468]

I think that's a logical explanation and I've heard that it will explode in the next couple millions years or in even 100,000 years. What we are observing could possibly be part of the stages of a star's final time. It would take the light from Betelgeuse about 642 years to get to us, and I agree with Michael Varn that I would love to see it.

 

[Helio]

Speaking of brightness, I'm curious how Betelgeuse is the "alpha" star when Rigel is about 1.5 magnitudes brighter?

 

[Catastrophe]

This is from "The Sky at Night" October 2020 page 11:

QUOTE
A stellar "sneeze" was responsible for Betelgeuse's unprecedented period of dimming at the beginning of the year . . . . . . . . . Its brightness is known to vary slightly, but in October 2019 it dimmed dramatically and by mid February it was around three times fainter than normal. The star then recovered, and by April was as bright as ever . . . . . . . . . Fortunately . . . the star had been monitored for months . . . by the Hubble Space Telescope ... examining it in the ultraviolet wavelengths needed to see the hottest materials surrounding the star. 'With Hubble we had previously observed hot convection cells on the surface of Betelgeuse and in the (autumn) of 2019 we discovered a large amount of dense hot gas moving outwards through Betelgeuse's extended atmosphere' (says . . . Harvard Smithsonian Center for Astrophysics. 'We think this gas cooled down millions of miles outside the star to form the dust that blocked the southern part of the star which was imaged in January and February.' "
There are images with the caption: " 'Stellar sneeze' : a huge outburst of gaseous material from Betelgeuse is believed to be responsible for blocking out its light."
Four images show dust cloud moving from "SW" towards "NE" until its leading edge reaches the star's centre.
QUOTE

Cat

P.S. Just seen two page coverage of similar content in "Astronomy Now" October 2020.
This concludes:
"With additional Hubble observations having taken place at the end of August, there may be further twists and turns to come before the debate s settled".

 

[Catastrophe]

Speaking of brightness, I'm curious how Betelgeuse is the "alpha" star when Rigel is about 1.5 magnitudes brighter?

Hi Helio, both stars are quoted as being variable. Wiki (apart from current episode) quotes Betelgeuse as apparent magnitude 0.00 to +1.6 and Rigel 0.05 to 0.18 so I guess they took the brightest each star reached and designated alpha and beta accordingly, even if the beta is brighter than the alpha for most of the time.

Cat

 

[Helio]

Hi Helio, both stars are quoted as being variable. Wiki (apart from current episode) quotes Betelgeuse as apparent magnitude 0.00 to +1.6 and Rigel 0.05 to 0.18 so I guess they took the brightest each star reached and designated alpha and beta accordingly, even if the beta is brighter than the alpha for most of the time.

Cat

Oops, I see what I did. I was enjoying APOD's "Orion in Depth" view and confused Bellatrix with Betelgeuse to get that large mag. difference.

The magnitude range you accurately state I think argues that Betelgeuse would far more often than not be dimmer than Rigel as Rigel stays close to 0 mag. but Betelgeuse swings from 0 to 1.6 mag., as you note. So I'm still a bit puzzled.

My wild guess is that our atmosphere favors reddish stars over bluish stars in light scattering. Betelgeuse may appear brighter except at higher altitudes, since red light has less atm. scattering. Is this a possible scenario? Included in this guess is the idea that traditional naked-eye views of long ago may be respected rather than trying to change things now. [Like the yellow Sun story. ]

 

[Catastrophe]

Oops, I see what I did. I was enjoying APOD's "Orion in Depth" view and confused Bellatrix with Betelgeuse to get that large mag. difference.

The magnitude range you accurately state I think argues that Betelgeuse would far more often than not be dimmer than Rigel as Rigel stays close to 0 mag. but Betelgeuse swings from 0 to 1.6 mag., as you note. So I'm still a bit puzzled.

My wild guess is that our atmosphere favors reddish stars over bluish stars in light scattering. Betelgeuse may appear brighter except at higher altitudes, since red light has less atm. scattering. Is this a possible scenario? Included in this guess is the idea that traditional naked-eye views of long ago may be respected rather than trying to change things now. [Like the yellow Sun story. ]

Once again, it all comes down to semantics! If you define the brightest star one which is brightest for only one nanosecond, then that is technically correct. If you accept the next one which is brightest for 9.9999+% of the time - that is just what you call what you call what id est semantics.

Cat

 

[Helio]

Once again, it all comes down to semantics! If you define the brightest star one which is brightest for only one nanosecond, then that is technically correct. If you accept the next one which is brightest for 9.9999+% of the time - that is just what you call what you call what id est semantics.

I'll consider this another one of your bright observations.

 

[Catastrophe]

Well, thank you, kind Sir!

Coming back on topic, what do you think of the latest magazine quotes? They seem to me to be a more than adequate explanation to B's variation in magnitude.

Cat

 

[Helio]

Well, thank you, kind Sir!

Coming back on topic, what do you think of the latest magazine quotes? They seem to me to be a more than adequate explanation to B's variation in magnitude.

Cat

The latest article I think I've seen, perhaps on this board, supports the expulsion of gas/dust that cooled and blocked some of the star's emissions. The original one from the scientists that I saw a few months back stated it as, "the fainting spell is due to expelled gas". I know I should be more mature, but it has helped me pay more attention to it, perhaps. [I will try an quit quoting that one for all our sake.]

 

[Catastrophe]

My apologies for being a bit brief with the "Astronomy Now" [October 2020] article. It is a double page spread dealing with both the ideas of gas coming from the star and cooling, but also with the idea that it may 'just' be a cool spot.
It concludes:
"One possibility to explain all the data we have right now is that there was indeed an ejection of dense gas from the hot part of a convective cell, which has left behind only the cool part, creating a cool spot on the surface, which led to the dimming."
Either way, I find the explanation very satisfactory. It is, after all, very similar to the idea of sunspots, with which we are familiar.

I must have missed it earlier, but I was pleasantly surprised to learn that the
very few stars as large as Betelgeuse can now be resolved as discs by powerful telescopes on Earth, such as the VLT. Images taken by the SPHERE instrument on the VLT show considerable darkening on the "SE" quadrant between January and December 2019. This looks more to me like a large cloud than a sunspot.

So, for me, "the clouds have it".

[For non-UK readers, this alludes to the announcement by the Speaker in the Houses of Parliament. "The Speaker ‘puts the question’ at the end of a debate. MPs shout “Aye” or “No” and the Speaker says “I think the Ayes (or Noes) have it”. If this judgement is challenged by further shouts of “No” (or “Aye”), the Speaker calls a division, saying “Clear the lobby”. "]

Cat

 

[Helio]

There is an interesting article in the latest S&T mag. They took the Kepler data of 150k stars and found about 500 that showed periodic results that revealed their rotation rates. They found a correlation between star rotation and age for stars as massive as the Sun or larger, and those were the easier ones to detect.

Betelgeuse would be one of easiest of all stars to see a periodic result due to rotation of a cool spot, so perhaps this was mentioned in the article, but if not, it should have been. This would also favor the cloud hypothesis.

 

[Catastrophe]

Helio, I cannot find a reference to rotation speed of the cold spot in either of the October 2020 articles I referred to (although I did of course mention the cold spot (vide "sunspot" analogy), but it is well known that it is estimated as 30 years.

"The Betelgeuse star has a rotation period of about 30 years. With this discovery, published in Astronomy & Astrophysics on January 9, 2018, a scientific team under the direction of Pierre Kervella, astronomer at the Paris Observatory, opens new avenues to understand the mechanisms of loss of mass of this type of supergiant star." Wiki.

A very useful article is:

https://www.observatoiredeparis.psl.eu/the-slow-rotation-of-the-red.html?lang=en#:~:text=The Betelgeuse star has a rotation period of,of mass of this type of supergiant star.

At first this (30 years) struck me as very high, but if you think of the much quoted ice skater model - and give her 5 mile long arms to extend - that solved the problem for me!

Cat

 

[Helio]

At first this (30 years) struck me as very high, but if you think of the much quoted ice skater model - and give her 5 mile long arms to extend - that solved the problem for me!
Cat

Yes, I obviously failed to consider how slow it could be rotating after all that expansion. If ice skaters could extend their arms that much it's a safe bet that none would be standing for long, if on tip-toes.

I found a paper showing it has a rotational vel. of ~ 15kps, which would put its fastest rotating region with a period of about 8 years.

The S&T article correlates slowing rotation with age due to magnetic drag as gases are expelled over eons. Since this was a study for main sequence stars, the expansion factor wasn't very important.

 

[Catastrophe]

Helio

"slowing rotation with age "

Is this not a function of entropy?

Cat

 

[Helio]

Helio

"slowing rotation with age "

Is this not a function of entropy?

Cat

Well, it is for you and me. But not for stars because it's reversible, at least the part due to expansion (ice skaters), but the magnetic drag portion as this would likely not be reversible.