White Dwarfs and Degenerate Gases

[@ComradeArthur]

43:06 "I can't do the animation ..." That's what grad students are for!

[@jefflyon2020]

I have learned so much watching these videos and taking ALOT of notes, love your clarity and pace you set with lectures.

[@probablyjustme77]

Criminally undersubscribed.

[@maxfmfdm]

this channel is an instant sub for me

[@mysticcity312]

😅

[@leezebede4469]

Lol. You said this 4 yrs ago. It's 2023 and it's still under subscribed. Shame this channel is one of the best

[@anautisticman7908]

For real!

[@tshinangakeith5819]

You are the best Prof. On a Sirius note, I can feel your astronomical passion in your videos.

[@jblangcua2726]

“sirius note” lol

[@marcuspradas1037]

Thank you for this lecture! For some reason I’m a fan of white dwarves. I find them fascinating. And I must be grateful to them, since while searching for videos about these "stars" I bumped across your Channel. This was my first video and now I’m seeing all of them and growing surprised seeing that the views doesn’t track with the extraordinary quality of these lectures. Yet there’s one question that I haven’t been able to answer yet. Many videos and podcasts say that when a white dwarf surpasses the Chandrasekhar limit, collapses and that ignites the C/O fusion in a Type I supernova. But to my understanding, if this limit is surpassed, then the atoms disappear, they become a neutron star. There’s no C or O to burn. I’d be very grateful if somebody here can explain me this.

[@JasonKendallAstronomer]

Glad you like the videos! The atoms don't "disappear", but rather, the entire star undergoes one big nuclear fusion event all at once. This is due to the electron degeneracy that's "holding up" the star to fail all at once. What this failure really means is that matter (stripped electrons) being added to the degenerate matter must be moving around with respect to all the other electrons at the speed of light. This doesn't work, so the degeneracy pressure fails. This ignites a runaway explosion that is extremely difficult to model with computer simulations, as it happens on such a large scale and so quickly. In sum, the atoms don't disappear; that's more in the realm of black holes.

[@innertubez]

Searched “white dwarf” videos >20 min should have know a Jason Kendall video would pop up. Thank you!!

[@JasonKendallAstronomer]

Ha!

[@rhoddryice5412]

Another cute cat clip. The thumbnail do resemble a cat. 🐱 Oh and I really enjoy your lectures. Hard to find enough time though.

[@jamesgornall5731]

Love your lectures Jason, you deserve to have more views, mate

[@Dragrath1]

Note there is also white dwarf crystallization where the star undergoes a phase transformation this was predicated many years ago but was recently confirmed by Gaia's observations as an over density of White dwarfs on the HR diagram where the phase transformation occurs (about 4 months after this video was uploaded) sci.esa.int/web/gaia/-/61046-white-dwarf-cooling-sequence-and-crystallisation

[@JasonKendallAstronomer]

I should do an addendum video.

[@cikgunirmell6958]

Such an amazing lecture and content, Thank you so much

[@LuciFeric137]

Thank you Professor.

[@rogerphillips4211]

I thought this was about Peter Dinklage eating a nacho plate with extra hot sauce🌮🌯

[@markphc99]

Thankyou for this channel

[@pipertripp]

This was a really nice intro to degenerate gases, something that's really hard to find out there so thank you for that! I noticed that you didn't bring up the maxwell-boltzmann distribution in "normal" gases and the comparison to a degenerate gas. Any specific reason for that or just trying to keep the discussion under 1.5 hours? :)

[@JasonKendallAstronomer]

Yeah, that's pretty much it. It's long enough as it was. Strictly speaking, I should have done so, and it's a major oversight. However, I also know that there are excellent texts and resources already out there for that. Here is my list of texts that are good for reading up on it... "Thermodynamics" by Fermi "Understanding Thermodynamics" by Van Ness "Introductory Statistical Mechanics" by Bowley and Sanchez "An Introduction to Thermal Physics" by Schroeder

[@no_more_free_nicks]

That was absolutely brilliant explanation of the fact that white dwarfs expand in momentum space instead of the normal space when mass is added to them. I never understood what it meant, until now, and it seems so simple now!

[@JasonKendallAstronomer]

Thanks! I've always liked the packed-subway analogy. It's fun.

[@zachreyhelmberger894]

Thank you for the great video! But I'm confused. At 17:30, you said a teaspoon of WD material would weigh five tons, but at 21:50 you say that it is 3,000 tons per sugar cube. Did I misunderstand something?

[@JasonKendallAstronomer]

No. I just misspoke. The density shows that it’s about five tons per teaspoon.

[@zachreyhelmberger894]

@@JasonKendallAstronomer It happens top all of us! Thanks again for your teaching on such a mind blowing topic! I have a bachelors of physics and was always fascinated by all these weird and incomprehensible things.

[@christopherreed2694]

So if we remember everything your saying dose that mean we are astronomers?

[@dirkbastardrelief]

Now I know how Tyrion Lannister came to be

[@drinkxyz]

You're saying the degenerate gas /electrons in a white dwarf can't cool down due to the nature of quantum mechanics and gravity. Heat however can radiate from the nucleic matter. In trillions of years it would become a black dwarf, but the electrons would still be "hot"?

[@JasonKendallAstronomer]

Strictly speaking electrons in the electron degenerate gas can be thought of as being at absolute zero. It takes energy energy to lift them out of the degenerate state.

[@drinkxyz]

Very interesting stuff. Hypothetically, if the gravitational pressure were somehow significantly reduced to say 1% of the previous level, what would happen? Would that be enough to switch it back to a normal gas? These higher energy electrons would probably be expanding, settling into lower energy levels, and radiating massive energy, bouncing into each other, and thus becoming at least temporarily, actually hot, even in a black dwarf? Maybe even an explosive expansion? Really weird stuff.

[@knuckles1006]

Can someone explain how an 8 solar mass star ends up being only a 1.2 or 1.3 solar mass white dwarf star?

[@JasonKendallAstronomer]

There is significant mass loss during a massive star's late life with a stellar wind, and pulsational instability. The star basically puffs itself apart, like a car sputtering on fumes as it runs out of gas. That rattles the car hard, and can cause damage to your car. Same with a star, but the damage is a wee bit more.

[@knuckles1006]

@@JasonKendallAstronomer Thankyou

[@borttorbbq2556]

Hmm if I remember one of the stars is feeding on the other as they pass close and its predicted to cause a type 1a super nova if I recall (no clue yet if you mentioned it or not but I think its kinda cool) I think its the dim star is feading on its larger brother but no clue

[@JasonKendallAstronomer]

Yes. That’s the idea. A close binary that can transfer mass due to proximity and changing physical diameter of the aging star.

[@manw3bttcks]

@wolfie Butler Do you mean Sirius A and B in particular? Not in their case, the orbit is too big for significant mass transfer to occur with Sirius A and B.

[@megfoster9577]

Chandrasekhar was only 19 years old by the way!

[@JasonKendallAstronomer]

Yeah, that does make it just beyond. It's true that often we cannot understand the gulf between ourselves and someone of great ability. To them, it's nothing, to us, an unbreachable gulf.

[@daveanderson718]

GOOD STUFF

[@vernonvouga5869]

Okay so if they centered on Sirius A, which direction is the farthest point of Sirius B facing? Just wondering, honestly I want to see how far Sagittarius A star has influence... are we literally an accretion disk?

[@vernonvouga5869]

Honestly I think our best bet is studying the Galaxy that we're living in first, and then expanding out for the rest of the universe, we have plenty of time before the Andromeda Milky Way Collision.

[@Kombrig_2]

I really enjoy your lectures, Mr. Kendall! However, I've noticed a couple of major mistakes. #1 Speaking of the binary system Sirius, how could you say that it's located in 7 l.y.? Sirius is 8.6 l.y away, Jason! #2 I was glad to know that a progenitor star for Sir B was 5 sol mass. But... this is just F4 type, Mr. Kendall. Class B stars 9-0 are 16-22 sol masses. So, Sir A star is just F8 type (2 sol m, 3 times diam, life span 1-2 bn yrs). Sirius A is gonna last maximum 0.5-1 bn and then goes to a red giant phase. The matter is going to slam to Sir B and in a couple of 1000-s of yrs we're got 1a SN just around the corner! Think about that, Dr. Kendall...

[@JasonKendallAstronomer]

Thanks for the correction. Can you give the timestamp for it so that others can be wary? I do try my best to do these in one sitting and one take for a reason. As for the other, I’ll take a closer look. Do you have an Arxiv article or AAVSO or PASP article to reference? Just curious.

[@Kombrig_2]

@@JasonKendallAstronomer Thanks for the answer, Jason! I'm gladly give you 2 links: kzbin.info/www/bejne/pWeopamJq7ajatU kzbin.info/www/bejne/jXete6aoaN6sl6c Learn a different types of a stellar classifications (3 of 'em) ...and you realize that only A & B classes can produce type II SN. F class stars are 1.5 -- 8 sol m. So, they end up as a WD. I really appreciate your info about Sir B (5 sol m progenitor) -- this has solved my problem: why a WD exist near by a Sirius A?

[@ioanbota9397]

Realy I like this video

[@LostPlanet2024]

I am often described as a white dwarf with degenerate gases.

[@achintgupta7256]

Is fermi gas opaque or transparent

[@JasonKendallAstronomer]

Not sure. Likely it would be opaque. Remember that transparency men’s that the wavelengths of light transmitted through a material have to either much longer or shorter than the inter-electron spacing. That makes it hard to answer

[@hornetobiker]

teeter totter? do you mean seesaw? merkins!

[@johnathanhenley2251]

you guys, shut up. this is Sirius.

[@JasonKendallAstronomer]

The is Sparta.

[@richardgraham1167]

​@@JasonKendallAstronomer yep, it's a tough crowd

[@mysticcity312]

😅

[@DrDeuteron]

No, this B Sirius