Classification of Stars: Spectral Analysis and the H-R Diagram

So we have made it through the dark ages, and are now a few hundred million years into the lifetime of the universe. There are plenty of stars all over the place, but are they all the same? How can we classify stars? Let's go through the basics of the Harvard System, and then take a look at something called a Hertzsprung-Russell diagram.
Watch the whole Astronomy/Astrophysics playlist: bit.ly/ProfDaveAstronomy
Classical Physics Tutorials: bit.ly/ProfDavePhysics1
Modern Physics Tutorials: bit.ly/ProfDavePhysics2
Mathematics Tutorials: bit.ly/ProfDaveMaths
General Chemistry Tutorials: bit.ly/ProfDaveGenChem
Organic Chemistry Tutorials: bit.ly/ProfDaveOrgChem
Biochemistry Tutorials: bit.ly/ProfDaveBiochem
Biology Tutorials: bit.ly/ProfDaveBio
EMAIL► [e-mail]
PATREON► / professordaveexplains
Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!
Amazon: amzn.to/2HtNpVH
Bookshop: bit.ly/39cKADM
Barnes and Noble: bit.ly/3pUjmrn
Book Depository: bit.ly/3aOVDlT

[@marchurtubise4722]

My man Dave out here making sure I pass every test in class

[@jenniekai3851]

Our science teacher played this video in our class and heck it was awesome and really helpful. Thanks proffesor!

[@Jacob-zk1jy]

Take english not science. I bet you can guess why.

[@jmike2039]

@@Jacob-zk1jy what the fuck is wrong with you?

[@youdononeetokno]

@@Jacob-zk1jy he can take take both

[@Strype13]

Professor Dave is certainly firing gigantic knowledge missiles.

[@commtheguy]

Figures

[@official_dulkai]

YES loll

[@0irtgud]

I'm a 4th year computer science major taking an astronomy class as one of my final electives. My finals tmrw and I'm ready, but Dave really clutch out here. 11/10 content.

[@doppelplusungutmensch1141]

I like your intro. You say hello. You say the topic. You start the intro. And that's it! Eight and a half seconds and the topic starts, no gibberish, no ads, no clickbaiting, no silly long intro song, no minutes-long introduction of who you are, and no waiting for what the video is about in the first place.

[@tom2443]

I hate to admit this, but I used to think all the stars in the night sky were planets... I didn't know what a "star" actually was. Now thanks to you Dave I know what a star is! (And many more things) Thank you.

[@tom2443]

@Kate Moore thank you! 😊

[@rheiagreenland4714]

Yeah i used to think jets in the sky were rockets going to space 😂

[@midnighthope7752]

My personal favorite is Only Bad Astronomers Forgot Generally Known Mnemonics

[@ProfessorDaveExplains]

that's a good one

[@needsleep1207]

This guy is awesome. If you were just a bit wacky you'd be a modern Bill Nye. Your knowledge and explanations are some of the best i have found. Thank you for your time.

[@whome5933]

I love the content and the simplistic explanations you provide. Thank you. 👍

[@Sasquatch1s3r]

Oh Boy An F Grade Kills Me

[@aestheticart4955]

Perfect! 😂

[@dotlessi1710]

O star:Oh! B star:Boy!

[@cbarona42]

Orwell's Book Animal Farm Gives Kids Migraines

[@rheiagreenland4714]

​@@cbarona42bro so frr

[@swiftmatic]

Oh, Be A Fine Girl, Kiss Me.

[@chubbybunny4570]

Thank you for explaining this is great detail. My professor was making this very confusing for the whole class

[@sahelanthropusbrensis]

It was always counterintuitive to me that red is cooler than blue.

[@DeluxeSlayer]

Not really I mean blue is a shorter wavelength which means more energy and more energy = hotter. Besides you can see it when a metal is heated enough ot will go from red all the way to blue.

[@sahelanthropusbrensis]

@@DeluxeSlayer i know the Physics of QED. But, for some reason, when i was a kid, i always thought that red was a hot color.

[@DeluxeSlayer]

@@sahelanthropusbrensis Oh I get it my bad

[@sahelanthropusbrensis]

@@DeluxeSlayer No problem man👍

[@kun_fu_taco4775]

Think about a torch with blue flame vs a lighter with yellow flame. The torch is hottet.

[@maskim3]

Thanks for that precious video man !

[@anthonywilliams8956]

Great video! You explained very well and the graphs were an added bonus!

[@triciamaeguerrero172]

Thank you so much for this video Professor Dave!!! You really helped me understand H-R Diagram in the simplest way as possible. I'm so thankful that I discovered you. I'm looking forward to watch your other videos especially the classes are now online because of the pandemic. I really need a study buddy to help me understand more the lesson. Again, thank you so much!! If I turn 18 years old and have a credit card, I'll make sure to join your channel. That's the best way to thank you for all the help. More vids and stay safe!!! xoxo

[@rporta]

great series, easy to understand and informative

[@ahmedsenussi8232]

Thanx for helping me to understand just that little bit better you make this subject fun aswell

[@harold_Shitmum]

Nice one Dave.

[@tructruc4369]

Very helpful! Today I'm so glad that I figure out such a wonderful channel like this

[@Snomrade]

This is helping me satisfy my current hyper fixation which is learning as much as I can about stars

[@Emcee_Squared]

Another great vid!

[@bibekluitel6113]

Professor could you please explain me about the AGB stars and its types?

[@timthefinner]

Awesome series as always :)

[@neshil]

Thank you so much ❤️❤️

[@official_dulkai]

Love this series 👍❤

[@Papa-ee8yr]

❤ wonderful explanation

[@CheddaWhizzy]

I'm guessing this is how they detect atmospheric temperature on exoplanets? right? Through their spectra, that is. I know this video is about stars but can this be applied to exoplanets as well? Thanks for a response.

[@gupdoo3]

"feel free to change it depending on your persuasion." [sweats in bisexual]

[@tornglory5709]

bruhbrhbruhbruhbruhbrurbhrburbhrburbhrbuhsyw hbyu5e8p9 yha 4s3890

[@FuriousMaximum]

PFFFFFFFFFFFFT

[@AbhishekSingh-hu4ky]

Good work

[@CoxDannyJ]

3:20 is this the same kind of thing that we see with fire? Like how a blue flame is hotter than a red flame?

[@givenflame1008]

Thanks Jesús, now I know more about Star clasification

[@djchemtalk2946]

Super info... thx prof

[@iffatsid8998]

This is what I needed

[@-Tofu.-]

I’m not here because I have tests, quite the opposite really, I’m on my summer break. I was just scrolling through KZbin and your channel. I’m hooked! It’s very interesting, I’m feel so smart now 😂.

[@abhyuday1294]

But i dont understood that why there are varaities of stars? Please tell me the reason behind it ??

[@kalpanasharma4249]

thank u soo much

[@rameshmantha1015]

awesome narration

[@afriendofafriend5766]

When you said red giants were cool but luminous, I thought you meant cool as in interesting.

[@timthefinner]

Looking forward to your explanation to dying stars

[@ParaSpite]

Large stars are inefficient and burn fuel too quickly. They have to be disassembled until the remains are small stars or inert hydrogen storage objects. That way, life around the star can be maintained for far longer.

[@ethankjt7277]

Yea g type is my favourite. Yellow is my favourite colour. But orange stars are shown to be the best stars for habitability if we ever relocate

[@knowledgegravity6904]

Tq tq tq tq tq tq tq tq tq tq very much sir it helped lot for my exam

[@korkutalekberov7116]

What about T 8 type star They are the coolest stars

[@andreagalang119]

@Jay Galang

[@fredodokonyero1044]

so elaborate

[@Capin_KO]

You know what, I'ma subscribe! Why not!

[@lumpyspaceprincess6335]

Is this for high school or coullage (I don't know anything about US' circulum)

[@rheiagreenland4714]

high school astronomy

[@lydiat.2038]

I am living for the intro

[@belgiumball2308]

You saved my face because i had an astronomy exam

[@jonathanmcastardo4282]

Thanks professor i answer my exam because of you thaaaaannnnnkkkksssss

[@albireothestarthebacklight2990]

Some of the coldest red dwarfs are not even M type, but rather L type, which is usually a classification used for brown dwarfs. These L-Type red dwarfs are around 2,500-3,200K. They are also very small and very loosely held together. They are barely even stars at all, and are around 0.08-0.22 Solar Masses.

[@bartonpaullevenson3427]

Absorption spectra, not emission spectra.

[@AvroBellow]

Main Sequence Stars: Spectral Class O -> Indigo/Violet * Spectral Class B -> Blue * Spectral Class A -> Green * Spectral Class F -> White * Spectral Class G -> Yellow Spectral Class K -> Orange † -> Ideal star type for life as we know it. Spectral Class M -> Red † * - These stars are always large enough to result in supernovae. † - These stars are never large enough to result in supernovae.

[@carultch]

Is there a particular reason why stars have that particular letter sequence to classify them?

[@Sundansulaku2023]

a is white and f is yellow white sun is g type

[@amlanbiswas4024]

professor can u make a video about Red Giant stars...i am eagerly waiting

[@ProfessorDaveExplains]

buddy that's covered in this tutorial.

[@googlebarbaralernerspectre2581]

K type stars are my favourite. Followed by white dwarves. Hopefully we can save the stars :)

[@binbingman]

The sun isnt white it is infact yellow due to its classification on temperature and absolute magnitude (brightness when it is at 10 parsecs away) . In main sequence star area it is classification G with its temperature being roughly 5000k and absolute magnitude of 6 , basic astrophysics .

[@rheiagreenland4714]

"Yellow dwarf" is just a misnomer G-stars are in fact white in visible light. They actually peak in green by the way. The sun only appears yellow in filtered images or due to atmospheric scattering of blue light. They are often associated with yellow to differentiate them from A and F type stars as well as white dwarfs

[@Mike_Toreno]

Asians when they realise that B class shines more than A class: My life is a lie

[@loveitftw]

💀

[@gwgaming8301]

i love getting baked AF and learning the secrets of the universe

[@whatarewedoing0]

why does the temp scale go down left to right? is that the norm, why? lol

[@curiousaboutphysics8605]

Cool ! How do you create such videos???

[@ProfessorDaveExplains]

adobe after effects!

[@curiousaboutphysics8605]

Professor Dave Explains oh! thanks for replying.

[@curiousaboutphysics8605]

And what about the intro???

[@jaimecampos9188]

Such a cool video. Nicely explained! Thank you very much :)

[@ReachSkyla]

Annie jump cannon is a badass name

[@w0lf667]

So are violate/purple stars are possible...?

[@rexisnox577]

Kinda but you would have to have super human vision to tell that they are.

[@FeedYourBrainChannel]

“Hey it’s professor dave. Let’s check out some stars” I swear his intros are insane out of context

[@darkseraph2009]

As an Elite Dangerous player, I don't necessarily need to remember the order of the main sequence, just each letter. So I often use the mnemonic KGB FOAM.

[@viriamiri]

ENA PFP!!!!!

[@FreeWay1066]

1:47 this is how I remember star classes, like for elite dangerous

[@raheemabdul1066]

0:09 a billion years into the history of the universe would be a billion yers ago isn't it? so about 12.6 billion or 1 billion years old?

[@MrMichealHouse]

What? He's saying following the timeline from the previous video, we're around a billion years in since The Big Bang.That's it. He's not saying now, today, he means since where we left off in the previous video.

[@bens.5127]

Anyone who would thumbs down such a great video must really live a miserable ignorant life. 😋🧐

[@DesertoftheReal-sl-1134]

Omniscient beings are firing gigantic knowledge missiles!

[@brianb8060]

Yep. That's easy to remember.🙄

[@IIGrayfoxII]

Sad that you didnt mention L and T class stars.

[@bartonpaullevenson3427]

Don't they (along with class Y) apply mostly to brown dwarfs?

[@Sundansulaku2023]

@@bartonpaullevenson3427 L0V toc L2V is still a star

[@bartonpaullevenson3427]

@@Sundansulaku2023 You're right. The criterion is at least 0.075 solar masses to initiate fusion in the core, and 0.075 Solar masses is about the average mass of a type L2V star (we think--unfortunately there's still a very small database of measured masses at this end of the scale).

[@argentinosaurus0096]

Did you Know: Relationship between Colors of the Star and Color of angry birds characters: O type = The blues B type = Luca A type = Matilda F type = Poppy G type = Chuck K type = Bubbles M type = Red

[@ethankjt7277]

It's very true

[@nugnugnugget8717]

Hi Dave

[@canbest7668]

I was talking to Dave. He says hi

[@Onio_Saiyan]

How I remember scoopable stars in Elite Dangerous: Always Be FuelinG Or Kill Myself. It's not good for the temperature model though.

[@brianb8060]

Growing up at the end of the cold war, I use KGB FOAM.

[@urworstnightmare.4530]

Does it mean that the blue part of the fire is hotter ?

[@Ignisan_66]

Yes.

[@Minderwaardigheids]

👍

[@ShouttoJesusChrist]

Good morning everyone.

[@wolfstar3883]

Good Mythical Morning!

[@paradis_4205]

No images? Just sound....

[@user-abd_almer313]

الهيدروستاتيكي ( حالة التوازن ) : السديم لديه قوة تجعله يتمدد وقوة تجذبه فيتقلص واذا بقت هذه القوة متماثلة فان السديم لن يختفي . كتلة الجينز : هي كتلة اكبر ببضع آلاف من شمسنا ، والجاذبية تنتصر عليها . عند حدوث اندماج نووي يؤدي إلى تكون حرارة وبالتالي تكون النجم . النجوم انواع : اصفر E-L ازرق A-D احمر M احمر غامق N 3,500k______________________________25,000k M - K - G - F - A - B - O كلما زادت حرارة النجم انفصل الكترون النواة عنها مما يشكل الحالة الرابعة البلازما . O : ازرق قوي ، B : ازرق ضعيف او سمائي ، A : رصاصي ، F : اصفر ضعيف ، G : اصفر قوي , K : احمر ضعيف , M : احمر قوي . يمكنك الرجوع إلى دقيقة - 3:15 . حلقة 4 . الاجسام الاكثر سخونة زرقاء والاقل سخونة حمراء . اذا اردت ابحث عن مخطط HR . الأصفر القوي هو الشمس او Sun .

[@zakiranderson722]

Only Bad Astrophysicist Feel Good Knowing Mnemonics.

[@Turi6070]

1:36 OBAma Funny Guy, Kills Me with jokes

[@vennstudios9885]

Is Dave a grade school teacher or university teacher

[@backstreetfan2887]

he used to teach organic chemistry at a college

[@plutoidrepublic2765]

as a 16 year old who plans to be a astrophysisct and am 2 years from graduating high school, i already know this stuff, but is there even MORE to know?

[@somebluestaroutinspace5625]

We stars have many things about us that have yet to be discovered. And the universe itself has many secrets it has yet to give up with space there's always something to find or discover.

[@robinchesterfield42]

My favourite mnemonic (including the brown dwarves): "Oh Boy, A Feral Giraffe Killed My Little Transparent Yeti" (with thanks to Crash Course astronomy. ;)

[@PsycoMyco6990]

This is a red cool video

[@cbrtdgh4210]

This topic finally makes sense. It is so poorly explained in textbooks.

[@stromghouls]

betelgeuse and antares are not red giant stars, but red supergiants.

[@Jasynatics]

Im a political science student and its common sense that this does have nothing to do with my course but just finished modern physics playlist and here i am relearning how the universe is formed. Feels like im back in junior high, its just that i feel like i understand it better than before.

[@xr-nm4nb]

Dave be out here learning us on shit

[@penguintime3853]

One slight mistake, O Type Stars Are 30000k, B Stars Are 25000K.

[@argentinosaurus0096]

Oh Be A Fine Girl Kiss Me. I was kissed by Winx Club.

[@carultch]

Or: Oh boy, Alex Filippenko gives killer midterms.

[@TheCorruptedPheonix]

The K type star is not red, it's orange.

[@bowrudder899]

This is definitely true: when I look in my solar scope, the star is small and red, and the scope doesn't heat up at all.

[@ethankjt7277]

Is the Sun white or yellow?

[@rexisnox577]

white but the sky distorts it to yellow.

[@ethankjt7277]

@@rexisnox577 then how is it called a yellow star?

[@marcellopierogi9209]

@@ethankjt7277 Perhaps because some people mean that it is a "yellow dwarf," another term for G-type main sequence stars (the Sun's type). Some of these stars are yellowish, while others (including the Sun) are white.

[@carultch]

@@ethankjt7277 If you see the sun from space through a neutral filter, it will be white. In fact, the sun defines what white is to our eyes, since our color vision is tuned to the sun's color plus the atmosphere adding up to white, as it is the dominant light source we can see our planet. Other stars in its class also look yellow, as it looks in our sky, thanks to the atmosphere scattering its light.

[@HugoFilho.]

Its white and also appears white during 80% of the day(in the place i live)

[@rigel533]

My type is B

[@somebluestaroutinspace5625]

Hey Rigel, it's been a few million years how are your fourteen planets doing?

[@alanlalonde6506]

OBAFGKM = orange 🍊, banana 🍌, apple 🍎, Fruit, grape 🍇, kiwi 🥝, mango 🥭

[@hornfancy8214]

Stars not drawn to scale

[@rexisnox577]

Obviously like they are bigger than the earth.

[@theunstoppableaxeofjustice3991]

I love K stars cause i live next to one G star garbage!

[@theirishtea460]

looks like i'm passing my test

[@LaneyTheOne]

O B A F G K M Also known to me as _scoopable stars_

[@donandremikhaelibarra6421]

‘Wait,oh be a fine guy kiss metal lamp to yell?’

[@cbnewham5633]

I can't believe anyone who is sane would find that mnemonic "sexist".

[@kayleelomas5598]

A little rude maybe if you stretch it, but sexist? No way.

[@amlanadarshdas4470]

It isn't