The G-Dwarf Problem - Sixty Symbols

Professor Mike Merrifield from the University of Nottingham discusses some new research into star formation.
More links and info below ↓ ↓ ↓
More videos with Mike Merrfield: bit.ly/Merrifield_Playlist
Mike on Objectivity: • Map of the Galaxy - Ob...
Mike on Twitter: / astromikemerri
The "G-dwarf problem" revisited - paper: arxiv.org/abs/2101.11022
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[@AgentWaltonSimons]

"Astronomers like to annoy chemists by referring to everything heavier than helium as a metal" - I already knew this, but it still made me laugh out loud for him to actually outright say that.

[@garethdean6382]

Chemists started it. 'There's organic chemistry, and then there's all the elements that AREN'T carbon.'

[@steppenhenge]

So kinda like the people who think anything with a distorted guitar is metal

[@Taeban42]

@@garethdean6382 Hey, don't lump us who like transition metal chem in with those buggers.

[@mikekeenan8450]

Try asking them about the allotropic form of hydrogen believed to exist at the centre of Jupiter and watch their heads explode. Presumably metallic hydrogen is not a metal, as surely as argon *is* a metal.

[@johnjones5220]

Came here to post this. I work as an organic chemist, think I might try out this definition of 'metal' today at work.

[@cluerip]

Brady always asks excellent questions. He understands enough (or appears to) to ask the best questions for us viewers. I especially liked him asking about what the professor sees in his head when he lies in bed.

[@Olhado256]

Brady's question-asking ability is definitely his superpower.

[@deprivedoftrance]

The right questions are at least as important as the right answers, maybe more

[@nickvanamstel]

Professor Merrifield you are a true treasure of the internets.

[@chakotex]

Hear, hear!

[@noel.gonsalves]

Is anyone else as blown away as I was by Brady's cake analogy? It's the kind you'd expect from a researcher on the team and yet he came up with it after just a few minutes of explanation by a leading scientist in the field and I really feel like acknowledging it.

[@snbeast9545]

I think Brady's ability to make analogies like that is enhanced by him having held these interviews for so long a time.

[@noel.gonsalves]

@@snbeast9545 definitely.

[@xevira]

@@snbeast9545 That and he has a level of understanding that can bridge between the experts and the layman, since he'd have to to be able to make such an analogy.

[@T3sl4]

It's a strong scientific tradition, e.g. the "plum pudding model". Though I don't know if that's why it came to his mind, or this was filmed just before tea time :)

[@mrdr9534]

@@snbeast9545 I agree that Brady's, by now, vast experience of making interviews has enhanced his ability to use this kind of "reasoning" and "explanatory analogies".. But I would go even further and claim that it is his ability and proclivity to use this kind of "visual/tactile/concrete-thinking" in combination with his ability to express and present them them as clear relatable explanations that has made him into the very successful "interviewer", "film maker" and "science communicator" that he is today... And this "quality" was something that I found in his work from very early on, and it is what has made me "keep coming back for more" and constantly look forward tohis next "creation" regardless of which subject matter it might "address". Best regards.

[@floydmaseda]

"That adds to the beauty of it, not detracts from it" Nice Feynman shoutout there!

[@condor6222]

Can you please explain it for those who don't know e.g. me :)

[@danielkerr4100]

@@condor6222 google is your friend

[@condor6222]

@@danielkerr4100 it's blocked in my country

[@RogerFingas]

On point: I’d never considered this issue, it’s fascinating. Off point: I’m worried Mike is going to hit his head on the wall next to him.

[@peterzinn]

Not off point at all. That will lead to more star formation.

[@donandremikhaelibarra6421]

our sun is a problem it’s a G2 star.

[@loyalsausages]

I know, I was thinking the same thing about that angled beem!

[@IanGrams]

I certainly agree that it's amazing we who exist for at most 100 years can begin to grasp processes that take many orders of magnitude longer to play out. Thank you Brady and Professor Merrifield for sharing that wonder with us :]

[@michaelcollins966]

i'm a simple man. I see a Mike Merrifield video, I click on it.

[@max_kl]

@MichaelKingsfordGray there was absolutely zero need for you to bring politics into astronomy and yet you did

[@Hyppotalamus]

I agree with the Professor here, the time scale of it all just makes it even more interresting. Like physics and chemistry happening on a completely different level we can barely observe.

[@Feetkiller97]

I love how proud I always get watching these videos like wow I understood something. You're all so amazing at explaining!

[@mattrace2]

I'm so glad to hear you say that. The communication of science to the public in a way that is understandable is one of the biggest problems I see in the world today. This is especially the case in US culture where the dissemination of science is very difficult due to the oversaturation of misinformation and disinformation that can be spread by anyone through Facebook message boards and random KZbin creators. Don't get me wrong, this channel is a perfect example of KZbin being used correctly, but a professional scientist from the University of Nottingham should be much more trustworthy than Joe blow making flat earth science videos. This channel is amazing, keep the videos coming!

[@bozo5632]

@@mattrace2 Either you like free speech or you don't. Also, I don't agree that it's harder to teach science to the public because of the internet. I would say it has only become possible recently because of the internet. Before that you only got it in physical classrooms, really for just a couple of years, and then, for 95% of people, you were done learning about science forever.

[@marklong8156]

⁷uïúú

[@placeswebreathe5814]

that animation at 4:05 casually blew my mind. i find it so easy to forget that there are more stars in every galaxy than i could ever comprehend

[@vtron9832]

Videos from this channel are a relief every time.

[@AlteredBuzzard]

Does Mike Merrifield have any Public Lectures on astronomy outside of Brady's channels? I could listen to him for hours about stellar stuff.

[@jadewhite766]

Prior to the current.. everything, it was fairly common for universities to hold lectures open to the public every so often. If you don't live close to Nottingham, you should try looking into your nearest university to see if they have any public events coming up (post-pandemic). There's many very passionate researchers out there who give excellent talks, beyond just those featured here.

[@Vmota123]

Can't wait for it to be adapted into an AnIME

[@malemusa7900]

What would be the genre?

[@mgancarzjr]

Netflix adaptation to come.

[@Vmota123]

@@malemusa7900 sci-fi/isekai.... "I can't believe I Got Reincarnated as a G-Dwarf"

[@legitbeans9078]

Full metalicity alchemist

[@askemervigbahnson333]

I would have appreciated if you had spent 30 seconds more on explaining what those graphs ment. What did the axis even mean, and why were there different units on the top and bottom of the x-axis?

[@mussalo]

Lower x axis: mass fraction of "metals" in a star (or the amount of elements other than H and He or just H). Y axis: ratio of stars with metallicity number lower than Z (x axis) compared to all stars (or how many stars have heavy elements less than the fraction Z). Upper x axis again shows the metallicity of a star but with different approach: it compares the metal/hydrogen ratio of a star to that of the Sun logarithmically. Negative and positive values corresponds to whether a certain star is less or more metallic than the Sun. The upper x axis is values I presume they measured and then converted them to the values in lower x axis. Nevertheless they show the ratio of "metals" to H.

[@kevinclements4962]

Love Sixty Symbols...with PBS Spacetime the best KZbin channels in their field.

[@Pfhorrest]

I would expect the explanation to be the opposite direction of cause from what Brady assumed: it's not that big galaxies get fed more gas because they're big, it's that galaxies that get fed more gas end up being big because they got fed more gas. Or if you think about it in terms of initial distributions of gas in the universe: places where there's lots of gas nearby able to clump together will make big galaxies that accumulate more and more gas over their lifetimes, while places where there's just a little bit of gas all by its lonesome will make small galaxies that don't accumulate much other gas in their lives.

[@guyh3403]

You're doing an excellent job Brady. Thank you for that.

[@norterrible]

Always love the Mike Merrfield videos. Nice one!

[@rhoddryice5412]

Are there any popular talks by Professor Merrifield available online?

[@FlavoredCrayon]

Wonderful video loved the perspective topic at the end. Thanks, Brady!

[@fspinacz]

Thank you for the amazing quality contents! Your mind is basically in par with these professors you interview because you catch these concepts on the fly and paraphrase it for us, more average people. Many thanks for your work and a nice approach where you ask such personal questions to make these great minds more human to us.

[@rc5989]

Fascinating work from Professor Mike and collaborators!

[@strawbertco]

did professor merrifield hit his head on the wallceiling directly behind him at any point when you were talking to him?

[@janwijbrand]

The topic is interesting, the contemplative ending was fantastic!

[@ComplexVariables]

Wow, I actually feel pride for our galaxy. Good show, Milky Way, ya dirty metal cad!

[@kevinhanley3023]

Thanks Brady and Prof. Mike.

[@gonwest]

Another great video. Thanks, Brady and Professor Merrifield

[@sixtysymbols]

You’re welcome

[@TheLuckyluc555]

very interesting as always

[@BillMSmith]

"there's nothing weird going on with the Milky Way" Er, humans! Always love a new MM/ Sixty Symbols video.

[@bozo5632]

I agree about MM/60 Symbols videos, but I tend to doubt humans are anything particularly weird, or that the milky way is well-characterized by human activity.

[@garethdean6382]

"Don't worry, that's a minor aberration that will go away soon."

[@Parax77]

humans?? that's just a clump of metalicity.. and on the timescales that are being considered are not even a blip..

[@WildBillCox13]

Fascinating. Liked and shared.

[@spud0124]

Great video!

[@walterkipferl6729]

Brady being an amazing interviewer again. Very nice video

[@Jobobn1998]

Man, I love Sixty Symbols. So damned good.

[@ThebestfamiIykeyb11]

These guys always release useful content after the exams! Great video

[@peterrose5260]

loved the question at the end

[@allthe1]

I don't why or who it may concern, but I loved the editing. Felt amazing

[@DamianReloaded]

It is pretty amazing indeed! I love sixty symbols, longtime fan! Keep 'em comming! ^_^

[@KirbyTheKirb]

Mike is great, very educational and knowledgeable with passion. Cool video, I never thought about the metals in stars this way, them being recycled when the star goes supernova and how the next generation star would contain more heavy elements. Very cool!

[@reidflemingworldstoughestm1394]

Currant astronomy is fascinating.

[@danielleriley2796]

I know this is Infotainment, but I love learning new things. I’m an aircraft pilot not an astrophysicist but I still love it.

[@PuzzleQodec]

Haha I lost it when you 'poured' gas onto the closed box. That was hilarious.

[@mrrn100]

"Huge symphony going on" now that's teaching!

[@gennadijanselm6720]

Interesting as every video 👍. These are very charismatic professors at Nottingham. Most stuff I do understand but there's always a tiny little bit in every video which helps extending my knowledge of physics and especially thermodynamics. Keep up the good work! 😀 Most valuable gift in this world is the gift of teaching. BTW: For videos on chemistry I recommend 《Periodic Videos》 as well.

[@sixtysymbols]

Thank you.

[@existenceispainforameeseeks]

I love this channel ❤️

[@nathanokun8801]

The comment on the sudden realization of the large numbers in the time it takes to do this in reality reminded me of a space-related joke cartoon in MAD Magazine in the 1960s: You see a man in a suit with a label NASA on his pocket looking at a bill for "Satellite Maintenance" on it with LOTS of zeros. The NASA guy's eyes are bugging out with shock. Next to him is little guy with a bad beard and a big, smoking cigar in his hand, in a grubby mechanics uniform and a beat-up baseball cap labelled NASA SATELLITE MAINTENANCE on the brim, saying, "We hadda take it to da shop."

[@PANZER7910]

3:06 ahhh, we love fancy 3D colorful graph.

[@lewistempleman9752]

Good vid 👍🏾

[@lewistempleman9752]

Great comment 👍🏾👍🏾

[@adamcummings20]

Good reply.

[@FrntRow]

Nice replying

[@danielkerr4100]

👍

[@sacredkinetics.lns.8352]

Beautifully explained. The Universe is a Symphonic Masterpiece. 💫👽💫

[@hebl47]

Fun fact: If you were to speed up time by a factor of billion, one second would still only represent ~30 years. So still very slow for even geologic events, let alone galactic! It would still take you 4.6 years to witness the whole life cycle of Sun from "birth" til now. And nearly 14 years to go back to the beginning of the universe!

[@YaMumsSpecialFriend]

Fascinating 🖖🏼

[@2Cerealbox]

I can't tell if Brady's shirt is an audio sample or a death metal logo.

[@sixtysymbols]

teespring.com/dire-strums-unmade-podcast?tsmac=store&tsmic=the-unmade-podcast&pid=387&cid=101811

[@vincentpelletier57]

If there was an upper limit to how massive a primordial galaxy could be, that would explain why massive galaxies would be "accreting boxes", since they could only be formed by collisions from smaller galaxies. Whereas the small ones we see are essential primordial galaxies, no large quantities of gas was added during their lifetime, and thus they are "closed boxes".

[@sjzara]

Is time dependent? After all, some of the initially formed stars are going to eventually supernova and spread metals even in the closed box, aren’t they?

[@bozo5632]

But those metals wouldn't form many new stars unless masses of gas were available.

[@sjzara]

@@bozo5632 But most of a star's mass is ejected in supernovas, so there should be plenty to form new stars. The result should be many fewer metal-rich stars than in an open box, but still metal-rich stars. I know I must be wrong, but I'm interested to know why.

[@bozo5632]

@@sjzara That's right, but it's relatively much less gas than would be present in a younger or larger galaxy. Star formation does continue, but at a slowing pace. Or that's what MM was saying, if I understood it. It seems to make sense.

[@giovannibattistaponzetto5860]

scratching my head: it may be linked to dimensions more than mass. for the same density, a bigger galaxy with uneven mass distribution would contain a point generating stars fast enough and dense enough to go supernovae and generating the heavier metals which would either be attracted by other near denser regions forming stars, or attract more H2 or HE and generate more polluted stars.

[@pystl]

I also do think that's it's pretty amazing!

[@AstroFerko]

10:32 I hope we figure out how to live long enough to observe the heat death of our universe. It's a shame we live for such a short time.

[@aresgalamatis7022]

@8:15 Wouldn't one expect for smaller mass galaxies to accrete less gas because the gravitational fields follows an inverse square law, mass and field strength are not linearly related? Have I missed something?

[@gordonmackie4519]

Isn't that Tim Hein's most amazing Money for Nothing rendition on Brady's T-Shirt?

[@nisargbhatt4967]

I didn't get what the M/H axis is for the closed box curve and why does it start from -1.0?

[@alexstauffer3359]

My step back at the start of this video was thinking how preposterous it is that stars go supernova. In our experience on earth basically everything just fizzles out: fire, cells, complex life, storms, eventually the planet itself. Stars give one final on encore which allows us to exist.

[@Asdayasman]

The Earth will feast on your body after you die. Just because you don't explode doesn't mean your death isn't useful.

[@maunaowakea777]

I know that you were summarizing, I would hope that you would change the narrative to include that most heavy metals are produced now by neutron star collision, not primary start production. We need to update our narratives.

[@garysilvester]

At around 6:30 when talking about the mass of a galaxy, I'm wondering whether that is just the observable mass or if it includes the dark matter mass of the galaxy

[@Jop_pop]

At 7:47, I would not expect scale-invariance, but that's because smaller galaxies should actually accrete more relative to their size than larger ones. Naively modelling galaxies as solid objects, surface area is proportional to mass^2/3, not to mass. And surface area is proportional to accretion rate. So accretion/mass is proportional to mass^-1/3. This means a smaller galaxy should accrete more relative to its mass. And yet we observe the opposite, which is even more surprising

[@Jop_pop]

Unless the accretion is proportional to number of stars which might be expected assuming 1) stars in large galaxies are the same size as those in small ones and 2) galaxies are very sparse And if stars in large galaxies are in fact smaller than those in small galaxies, we'd actually get the observed effect. I am zero percent an astronomer but I wonder if that could explain the answer to the g dwarf problem

[@lionhawk555]

Professor Merrifield referred to heavy elements being produced in supernovae. I thought that nowadays the prevailing theory was neutrn star mergers were largely responsible?

[@seansreading]

That's for really heavy elements, heavier than iron. He just means things that are heavier than helium, most of which are produced inside stars. And he's describing them being spread by supernovas, not created in them.

[@runrickyrun157]

This video came up in my home screen, but does not come up for me when I go to my subscriptions feed. Anyone else have this too?

[@michah5245]

Are the fire places in such old style houses, like that in the background of Brady, still in use.

[@feathercaine]

Obviously can't speak for Brady's one specifically nor for other countries, but at least in the UK quite a lot of houses have working fireplaces like that; they're not exactly standard or universal or anything but there's a fair amount of old buildings here in general, especially in some areas and cities, so they're not really uncommon either (:

[@draftnotion]

Could charged and dusty material fed into stars from colliding with the galactic current sheet account for the development of more diverse stars? Or would the resulting micro nova not be high enough energy to detect a changes in the star's elements?

[@KaiseruSoze]

So does this allow us to now come up with the age of a galaxy? Could the "gas" be dark matter? (there is far more dark matter in a galaxy than H2, or He) I would expect the earliest galaxies to have almost no metalicity. The lookback time and new galactic age calculation should match - yes?

[@bozo5632]

I know that gas has been ruled out as a dark matter candidate.

[@pbj4184]

Prof Merrifield is rocking that salt-and-pepper look 😁

[@flynnezrabeckman]

Could the added gas be from more mergers with other galaxies, and the small galaxies simply have gone through few if any mergers compared to the larger galaxies like ours?

[@JamesGaehring]

Does the % of dark matter in a galaxy play any role in whether it more closely fits the closed box model or the accreting box model?

[@MrMartinSchou]

I am curious - does being a low metallicity/small galaxy imply anything about the galaxy's age? E.g. are the oldest galaxies we know of low metallicity and the old monsters we know of high metallicity?

[@bozo5632]

They all start with low metallicity and it increases over time. So yes, it corresponds to age. And it increases less in smaller ones, according to MM here, so it's more than one factor - not just age.

[@BleachWizz]

If a closed box galaxies thar are these small galaxies starsts receiving more mass would it be able to start transforming into those heavy elements galaxies?

[@Philrc]

Brady I've just noticed that my birthday is only two days before yours weird huh? ( oh there's a lot of years separating us) I mean, what are the odds? and you make these videos and I watch them!!! is someone trying to tell us something?? _spooky_

[@Asdayasman]

I think the odds that two living people have a birthday is roughly 1:1.

[@Philrc]

@@Asdayasman erm...yes I was making a joke (duh)

[@rJaune]

So would you expect more terrestrial planet formation in Milky Way scale galaxies?

[@jimlake5404]

I wonder if the central black hole plays a significant role in galactic gas attraction. Did you look at that question?

[@dogcarman]

Great video. But you seriously need to lose that equalizer-like noise at the bottom. It’s quite annoying.

[@Jack__________]

This made me wonder... if you have a gas and put it in a container, the gas will diffuse to fill the container rather than bunch up in the bottom corner. And that is while the gas is under the influence of the earth's gravity. So if there is no major gravity well, and no container to cause a pressure, why does a gas ever collapse into a star? As opposed to just diffusing forever. Especially given that the electromagnetic repulsion is so much greater than the "force" of gravity.

[@ratandmonkey2982]

would have been nice to define the axes in the graph

[@tautologicalnickname]

Who also noticed the light saber on top of Brady's table behind him?

[@OmateYayami]

Are presented plots made in python's matplotlib? It kinda resembles fonts, colours, proportions and general style to me.

[@IllidanS4]

Non-programmers commonly use Python and everything that's available there.

[@AstroMikeMerri]

Yes - the plotter of choice for our PhD students.

[@OmateYayami]

@@AstroMikeMerri Thanks for a swift reply Professor! I can understand why, I've generated thousands of plots with it during my PhD, unfinished but surely matplotlib plots were published. I guess that's why it caught my eye. Cheers!

[@OmateYayami]

@@IllidanS4 Programmers too mate. I guess older pick gnuplot and younger matplotlib as their weapon of choice.

[@JoeyFaller]

The thing is, the human mind isnt comprehending scales of billions of years at all, though, we scale it down in our head immensely to what we're used to.

[@JoeyFaller]

Still impressive we can interpret these data as more than just abstract numbers but translate what actually is happening at that huge scale

[@rhoddryice5412]

6:37 log(M*/Msun) What does the asterisk stand for?

[@AstroMikeMerri]

Mass in stars

[@nNxiNgr]

It's a star.

[@rhoddryice5412]

@@AstroMikeMerri of course. Thank you, my mind was set on galaxies so I couldn’t get my head around it.

[@Konstantinos340]

So wait hows this reconciled

[@terryrogers6232]

I suppose that also means most larger galaxies in the universe formed not from a big blob of gas but must have acquired mass over the eons. Ergo, near all of the galaxies JWST will find far off will be small. No?

[@fep_ptcp883]

9.999 views. I feel special

[@redwormpiper3354]

Perhaps a silly question...where does the gas come from that is feeding these accreted galaxies?

[@DrFoetze]

I would guess they attract intergalactic matter due to their strong gravitational pull and there are no silly questions ^^

[@AbhijeetBorkar]

From the halo and circumgalactic medium. Sometimes also from the intergalactic-intracluster medium.

[@rhoddryice5412]

@@DrFoetze “... and there are no silly questions” TRUE. Second that.

[@docostler]

@@DrFoetze I'd just add there are no silly _sincerely asked_ questions.

[@phillyg7661]

Standard model star formation seems to give no relevance to electrostatics and how charged particles attract and repel, much stronger than gravity at that point. In that sense a hydrogen only star would need equal amounts of positive ions and negative hydrogen anions.

[@travisstrabala5218]

Why is the audio so quiet?

[@huskytail]

I don't think a small galaxy would pull as much material, percentage wise, as a big one. Aren't the smaller ones influenced by bigger galaxies, which are pulling the material to themselves and not leaving it for the smaller ones. Right?

[@jellorelic]

Not complaining at all.. but I am curious as to why this one went on Sixty Symbols rather than Deep Sky (and it's a crime how low the sub numbers are on these two channels).

[@celewign]

I thought the word "accrete" means to remove or throw out material. In this video it means to gain material?

[@garethdean6382]

'crete' gets attached to a lot of things. To secrete or excrete is to leak or emit something, accrete to gain it. 'Acc' is usually positive, like accelerate, acclimatize accept...

[@celewign]

@@garethdean6382 that makes sense thank you. Maybe I was confusing it with Ablate.

[@the_eternal_traveler]

☝️🤓I love this. Big thanks for all. 🙏💚

[@Tapecutter59]

Small galaxies feed the large galaxies via collisions.?

[@bobcabot]

...im not so sure that we really comprehend these time-scales: our brain is trying to compress time whilst it is yet a part of it - we are still in that "box"...

[@qwertymann1]

Mustn't it be that small galaxies are small because they don't run into gas, whereas large galaxies run into a lot of gas hence they are big?

[@garethdean6382]

Yes, the question though is whether a galaxy half the mass runs into half the gas or LESS than that. You might expect smaller galaxies to get less new gas, but for that gas to be more significant given the galaxy's tiny size.

[@arthurmuller671]

Tell me: why are there no more videos from Ed Copeland? I miss him so much.

[@Clevercomback]

THE GD Warf problem is that they haven't given him his own show yet! We all want to see Warf commanding his own ship and cruising around the galaxy dishing out his own brand of diplomacy! ...wait I think I read the title wrong.

[@harry.tallbelt6707]

Ok, what does Brady's shirt say, though?

[@sixtysymbols]

It’s this: teespring.com/dire-strums-unmade-podcast?tsmac=store&tsmic=the-unmade-podcast&pid=387&cid=101811