How Stars Work

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How stars work was a mystery until the early 20th century when astronomers learned to decode stars' spectra. Spectroscopy allowed stars' chemical make-up, temperature, and luminosity to be directly measured. Thanks to a spectral classification system developed by
Annie Jump Cannon, and the Hertzsprung-Russell diagram, it became possible to understand how stars are classified, and how stars live and evolve from the main sequence to red giant to white dwarfs.
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[@dukecity7688]

This is one of the best things that i have discovered. I am 67 yrs old. High school drop-out. Watching this and other's like this has fired my imagination and given me something useful. I try to take notes and understand. Sometimes i have to re-play footage because i really want to understand. Thank you for this gift.

[@LaunchPadAstronomy]

Wow, I don't know what to say except Thank You so much for those kind words! I'm glad you're enjoying the content and getting so much out of it.

[@doggonemess1]

It's heartening to hear that there are people who still yearn for knowledge at all stages of life.

[@joebloe1401]

Black History: Of the 12.5 million slaves taken from West Africa, 80% were sold to whites by Africans!! Black lives didn't seem to matter much to them!

[@gleysonoliveira802]

By far, this is the most underrated channel of the whole web. Thank you for another great video.

[@LaunchPadAstronomy]

Thank you so much Greyson, I’m flattered. Maybe someday I’ll become an overrated channel ;)

[@nirabhradas6375]

@@LaunchPadAstronomy I just found the channel tonight. And I seriously doubt it. I, for myself, do not think that the content of this channel can be rated even in an astronomical scale (pun intended). Thank you so much for making these videos. They make a very nice watch after programming all day. And I also get to learn new things!! Oh and also you got a new sub. I wish I could sub multiple times ;)

[@joebloe1401]

Black History: Of the 12.5 million slaves taken from West Africa, 80% were sold to whites by Africans!! Black lives didn't seem to matter much to them!

[@vasari9198]

It is no small thing that the writing on these videos is always excellent.

[@LaunchPadAstronomy]

Thank you very kindly:)

[@noseonscent1935]

You should have millions of subs,...seriously!

[@Locut0s]

Honestly this is probably the most comprehensive yet concise and easy to understand summary of stellar mechanics I’ve seen. Very well done!

[@LaunchPadAstronomy]

Wow, thanks so much!

[@huski1]

Best video on stellar evolution and general star stuff

[@joebloe1401]

Black History: Of the 12.5 million slaves taken from West Africa, 80% were sold to whites by Africans!! Black lives didn't seem to matter much to them!

[@patrickwalsh2361]

👍🏻I’ve never watched better videos than Christian’s!

[@LaunchPadAstronomy]

Thank you so much!

[@bbtran1111]

You made it so easy to understand. A huge help in class. Thank you so much!!! Can't wait to watch your other videos!! :)

[@LaunchPadAstronomy]

Happy to hear that, I'm glad it helped!

[@Dragrath1]

WNh stars like R136a1 are interesting in that weirdly enough they are fully convective largely due to being supported against their Eddington luminosity (the luminosity where the radiative pressure exceeds that of gravity ripping a star apart) by a torque meaning they burn through all their hydrogen not blown off in to space but constantly lose angular momentum what is mind bending about it is R136a1 is about 40% hydrogen meaning it has burned over half its hydrogen fuel supply. And yes its still burning hydrogen at its core and thus in effect it is a "main sequence star". Its weird spectral type comes from its convective properties mixing core burning products up to the surface and thus it has way more helium than a typical star and was origionally classified as a Wolf-Rayet star W type stars are either WN, WC or WO depending on whether they have dominant Nitrogen Carbon or Oxygen lines and have been split into the traditional Wolf-Rayet stars which are massive evolved stars that have blown away their outer hydrogen envelopes becoming hydrogen deficient and the Wxh stars which still have significant amounts of hydrogen and are really the absurd peak of the main sequence. The fate of stars like this are unknown observationally as they are just too rare but in theory these giants likely go out in a wimper or a blip as by the end of their lives they have next to no angular momentum left and an iron core way to massive (around 50 Msun) to form anything other than a black hole but thanks to the high mass loss not massive enough to produce a pair instability supernovae (64+Msun iron core). The uncertainty lies primarily in whether the supernovae shockwave of a star like this is able to escape or not making the difference between an unusually dim supernovae(gravitationally red shifted) or the star just blinking out of existence behind an event horizon. Also fun fact apparently 99% of R136a1's radiation is well outside the visible limit with a spectral peak of around 50 nanometers in the extreme ultraviolet which is just absurd in the awesome sort of way.

[@johnlamb2333]

Well done Christian, hope your students appreciate you, They should!

[@LaunchPadAstronomy]

Thanks John, I tried making the video for both my students and the general public. Hope they enjoy it!

[@backstreetfan2887]

wonderful, thank you so much for doing these

[@vf7vico]

your videos are true high quality mini-lessons, Christian -- very clear, well explained. thanks again for your great resource!

[@LaunchPadAstronomy]

Thank you so kindly, Victor. I really do appreciate it!

[@aresmars2003]

Great summary, reminds me of my stellar evolution class in college, with mostly grad students!

[@LaunchPadAstronomy]

Thanks! It's a bit distilled from the grad-level but I'm glad you liked it :)

[@adriantee5219]

Awesome and so so informative! Thanks so much!!

[@TheGunmanChannel]

You're a star 🌟

[@RobbieC67]

Awesome video! I so needed to see this video. I spend most of my time looking at black hole videos and the like, without knowing how stars are classified etc. This explains it great. I also love the section about the huge impact of women on astronomy. I love it! Love this channel. :)

[@LaunchPadAstronomy]

Thank you so much, I truly appreciate it!

[@levanataylor790]

Question about the HR diagram -- for stars on the main sequence, there's a more-or-less universal relationship between mass, temperature, and radius; but if it was really universal, the main sequence would be a very narrow line on the diagram, so why is it not?

[@erichschmidt1328]

This friendly neigborhood astronomer ist great. Thank you for your clips on youtube.

[@pipertripp]

Really nice introduction to stars. It's such a great topic. Looking forward to the next installment.

[@LaunchPadAstronomy]

Thanks man!

[@heroicrockstar]

Finally, an explanation I can understand, thank you 👍

[@XloH911]

You are a great teacher!

[@LaunchPadAstronomy]

Wow, thank you!

[@abhishekwadkar7606]

Nice video man keep up the good work

[@joedasilva134]

Thanks for sharing another great video . It is always a pleasure to know more about the universe. I am staying curious!

[@LaunchPadAstronomy]

Thanks Joe!

[@jamesdougan8789]

g`day christian thanks for the great video and congratulations on the sponsor good to see you have some time to make some videos again i have been missing yours and tony's content for the last few months good to see you back cheers james D

[@LaunchPadAstronomy]

Thanks James I really appreciate it. It's been a much crazier summer than I planned for but I'm making myself get back on track. There's a LOT more to come.

[@Dan5482]

Thank you for another excellent video.

[@LaunchPadAstronomy]

Thanks Dan, I appreciate it. It’s been a busy summer and I miss making videos so I’m glad to get back to it.

[@JonConti]

Hey Christian, great channel man, I found you on the The KZbin Creators Hub podcast. Have you ever considered throwing some background music onto your videos? I think you have a great voice but maybe some light mood music would enhance it a bit! Great channel man keep it up.

[@LaunchPadAstronomy]

Thanks! I did some videos with music before but I always struggled to find fit so I kind of gave up. But then some people said they liked it better without music, while others preferred music. Not sure if I'll reintroduce it again though it can be nice to have.

[@arcadia5607]

Awesome video. Thank you.

[@LaunchPadAstronomy]

Glad you liked it!

[@paulgrote7139]

Dude I’ve been studying the Centauri system for a while now- Proxima Centauri is so goddamn fun to say.

[@LaunchPadAstronomy]

It's a cool sounding name :)

[@donchamberlain7139]

Yes, very nice summary!

[@LaunchPadAstronomy]

Thanks Don!

[@sundayaito4366]

Great video....thank you....my favourite astronomer....sir, how about you do a video updating us on what scientists are doing about interstellar travel, means of propulsion, and a possible timeline in which a probe could be sent to alpha centurai. Also a video on the feasibility of warp drive will be appreciated. Thank you sir.

[@LaunchPadAstronomy]

Thanks for the suggestions, Sunday!

[@martinstallard2742]

big star's are like Rock stars, they live fast and die young

[@jimmyshrimbe9361]

I love that Star graph! Diagram**

[@LaunchPadAstronomy]

Yeah me too. It's the key to understanding stars!

[@LegionOfWeirdos]

Your opening had that song "Woodstock" running through my head. One of these nights I'm going to set up a time lapse like that! "Vega is a lot hotter..." That's probably because of the poorly-built carburetor and sticky throttle linkage Chevy used causing over-fueling. Welcome to my ADHD 🙃

[@LaunchPadAstronomy]

"We are stardust...billion year old carbon."

[@vdiitd]

Great video! One (may be) question though: How do you separate the spectrum of a single star among the cluster of stars? When we see the stars using a telescope, you may see a lot of them together. Then how to find out which spectral lines belong to which star?

[@johnjobs3027]

Error in sun's temperature shown at 7:57 . It should be 15,000,000 K and read 1.5x10⁷, instead of 1.5x10⁶.

[@tisstuart]

okay so now we have a yellow star? Other videos explain that the Sun is a white star, only the Earths atmosphere causing it to appear yellow from the ground. Why is there so much discretion on this? p.s. I really enjoy these videos. Making me question previous conceptions is good. Thanks Launchpad.

[@LaunchPadAstronomy]

Believe it or not, the Sun radiates most of its energy in the middle of the visible spectrum - which is green! But it also puts out so much in the rest of the vis. spectrum our brains just turn it all white. But the images of the Sun I used were taken in yellow filters to bring out surface details.

[@TheOicyu812]

0:51 - Not only are there more stars in the observable universe than there are grains of sand on all of Earth's beaches, but there are also more stars in the observable universe than there are grains sand on all of Earth's deserts.

[@AstroRamiEmad]

Sorry, I am still stuck at 0:52 ... Are there only 5 Billion Galaxies in the (Observable) Universe?

[@LaunchPadAstronomy]

More like on the order of 100 billion galaxies.

[@AstroRamiEmad]

@@LaunchPadAstronomy And how many stars on average a galaxy has?

[@arnavjain7566]

@@AstroRamiEmad 100-200 billion!

[@AstroRamiEmad]

@@arnavjain7566 The numbers don't seem to add up with me ... I mean there are 3 orders of magnitude difference.

[@SciFyerGaming]

Hey Christian, whats the whole deal with the fates of Canopus and Polaris Aa? Both are sort of on the iffy non-clear cut line between II (bright) and Ib/Ia (supergiant) stars, but both have masses less than 8-10 solar masses. After Canopus finishes its blue loop and goes back to a red giant is it more likley to become a normal AGB giant then a planetary nebula or will it become a super AGB/small RSG giant/supergiant and go supernova; and then whats the fate of Polaris Aa? Did Polaris Aa form with a initial mass above 10 solar masses, but it just lost a lot from its stellar wind, or is its classification purley based on its spectral lines and luminosity?

[@BMXaster]

This is such a cool video. But could you please share the source of that "Hertzsprung-Russel Diagramm"? I really want to edit it a bit and make it more pretty and the produce a few high quality posters for me, friends and family. Thank you for making this video

[@hl8333]

Its SAD that the Nobel prize isnt awarded POSTHUMOUSLY ❤😊

[@LaunchPadAstronomy]

🔴 WHOOPS! At 7:55 I quote the temperature as 15 million Kelvin, but write it as 1.5 × 10^6 (1.5 million) K . That should be written as 1.5 × 10^7 K. My bad. 🔴 Learn more about stars: kzbin.info/www/bejne/qYLIoKOafsuDg7M

[@boogieboss]

Stars are like big light bulbs in the universe.

[@Inertia888]

A painting of a Dark Star on the shelf

[@praisethesun69]

electric repulsion would be a rad band name lol

[@thethoth1755]

Wonderful channel, fantastic Host! Professor ,how do we know how old our star is ?

[@astronaughtpov]

A star's composition is a useful tool for calculating stellar age. Since the sun is constantly fusing Hydrogen into Helium, we can approximate its age by looking at the ratio of Hydrogen to Helium in the sun. In short, as the sun ages, it will be composed of more Helium and less Hydrogen

[@tinetannies4637]

If the pressure at a star's core is sufficient to create the conditions for fusion, why doesn't ALL the material at the core fuse at once, and do so progressively until it reaches iron? Why doesn't a star essentially burn through all its fuel immediately?

[@gregorysteltenpohl1440]

There is an image at 11:22 that is on my wall, could you please tell me what it is?

[@smeeself]

I think it's the LH 95 star forming region of the Large Magellanic Cloud, taken by Hubble in about 2006.

[@evilnorman9978]

Finally a channel where the material hasn't been reduced to moron level. Thank you!

[@sangramkapre]

@launch pad astronomy What happens to the leftover electrons before positive hydrogen nuclei collide to generate helium and energy?

[@LaunchPadAstronomy]

The temperatures in the core are so high everything is ionized. The nuclei fuse in a "sea" of free electrons.

[@rhoddryice5412]

I picked up a new one. Only Bad Astronomers Forget Generally Known Mnemonics (Lost They Yield)

[@Bullsleagueofbasketball]

sonwas the kindle fore your spirit

[@kagamifn9887]

Thk

[@LaunchPadAstronomy]

Cheers

[@puppetpatti]

So this means that Harry Connick Jr. is a Type O star! Woot! I've always thought he was HOT! 😁 I seem to always need a dictionary handy when watching your videos lol...Great stuff as always, thanks Christian!

[@LaunchPadAstronomy]

Dammit, Patti I'm an astronomer not a physician. I have no idea what Connick's blood type is.! ;)

[@puppetpatti]

@@LaunchPadAstronomy 😆

[@Inertia888]

Did Annie Jump Cannon write the first algorithm for astronomy?

[@MarkReedman]

Hi Christian Do you think that it might be possible that we may discover a new way of communicating without radio transmission and jump to the next level in Quantum communications, a Quantum leap. If so this may also be the reason that we don’t see other intelligent civilizations in the universe as they don’t use radio transmission for their communications anymore as the technology is only fleeting in their civilization’s evolution in the expanse of space and time and the age of the universe. It may be that it is only used briefly like fossil fuels and Cfc’s until a new method is found. SETI may be searching for something that is not there as like the stone age it’s old technology. Love the show

[@LaunchPadAstronomy]

The idea "they" are using non-radio communication has been one answer to the Fermi Paradox for some time now. I'd say it's not impossible, though I'm not convinced quantum tunneling is the mechanism.

[@aviavaodwheoieghfpiqbiqpo1663]

@@LaunchPadAstronomy Shouldn't we be able to see mega structures based on the light received from other stars though? We can tell if other stars have planets around them from observation, we would be able to tell if something unnaturally shaped was in the solar system as long as it passed by the telescopes sight. But we do not see this. Alien life should be much more common.

[@davidgibson121]

Stars are Gods fairy lights. Though I don't envy the task of rewiring them when a bulb goes.

[@LaunchPadAstronomy]

lol!

[@Bullsleagueofbasketball]

after yahoo, which site isnt yours

[@Bullsleagueofbasketball]

costed me myjaw

[@Bullsleagueofbasketball]

chair no distraction

[@Bullsleagueofbasketball]

last actually first one was

[@rhoddryice5412]

In (most of) Europe 10^21 is 1 trilliard

[@Bullsleagueofbasketball]

ship at windows enters tv watching it later on

[@Bullsleagueofbasketball]

they pushed me off a triple slide and i fell down the 100 ft hill new stident

[@radiobill4082]

I thought they were all horizontal or on their knees

[@Bullsleagueofbasketball]

wore the rim bc they took your first fb idea on facebook.

[@Bullsleagueofbasketball]

#1/#2

[@Bullsleagueofbasketball]

live address had 1 million views when he signed up and clicked a tabdissapeared

[@Bullsleagueofbasketball]

#3

[@Bullsleagueofbasketball]

youll have brick wall ideas but when she gets mad if your at one not playing it waiting to play poker while there brick wall is much worse

[@jimmyshrimbe9361]

I think you mean the sun is 1 solar mass** Hahaha jk

[@jimmyshrimbe9361]

Like what's the flux?

[@LaunchPadAstronomy]

Flux is the amount of energy radiating through a given area every second. Mathematically it's F = σT^4, where σ (sigma) is just a number. I probably could have explained this better in the video.

[@jimmyshrimbe9361]

@@LaunchPadAstronomy I was actually making a joke but your explanation definitely taught me more than I already knew!!! Thanks!!

[@Bullsleagueofbasketball]

How tobe from the bronx and tell a bronx story

[@Bullsleagueofbasketball]

when you were on house arrest and got hepc from a roomate of your mom, used to living with the father, and making facebook to doing something nobodys ever done, all bc ofna needle and thread orrigonally..wasnt it or

[@Bullsleagueofbasketball]

share

[@freddigglegmail]

all energy is pure

[@artemismoonbow2475]

Here is what confuses me and maybe it shouldn't. Our star is as close to the central point of the H-R diagram and everything is measured in relation to that as a ratio. Now is that pure chance? Or is the H-R diagram only possible to have conceptualized because of that fact and an exotic science would (ie an observer around another star) have to formulate another classification system to understand stelar relations? If your star was Proxima Centauri and you were trying to figure this all out using similar deductive processes, would the diagram look the same, but the labels that are comparative ratios just be the difference? If a different chart would have to be formed to make sense of the chaos, I wonder what effect that would have on the scientific frames that would result?

[@beta_cygni1950]

There's nothing special about our sun and the HR diagram. All stars' luminosities in the HR diagram are normalized to the luminosity of our sun simply for convenience, and nothing more than that. It just gives us a good point of comparison with other stars since we are all familiar with our star. And yes, the HR diagram would look basically the same if it were normalized to another star woth a different temp & luminosity. Its axis would be shifted (so that version of the HR diagram would simply be shifted left / right, or up / down), but its shape would still be the same.

[@artemismoonbow2475]

@@beta_cygni1950 Thank you for this. Cheers :)

[@Bullsleagueofbasketball]

and a counter was already bad

[@Bullsleagueofbasketball]

jumped by a wanted man already..how to not know

[@Bullsleagueofbasketball]

Stars a distractor?

[@pauldhoff]

Sorry but you have Hydrogen and Helium with the same spectrum absorption lines.

[@hayfield43]

How annoying. I thought it was how stairs work.

[@Bullsleagueofbasketball]

paftb

[@Bullsleagueofbasketball]

bc he loses . i didnt tell him boutpopcorn

[@Bullsleagueofbasketball]

shoulda got back of head

[@vik_body_beld7294]

Big bang theory question - big bang happened and creates 10 to power of 21 , sextrillion stars ! and all this was compressed into a dense thing the size of a marble ? The scale and size is beyond human comprehension, any other believable theory which can explain this?

[@LaunchPadAstronomy]

The conditions at the Big Bang would have been too hot for matter to form. Instead it was pure energy which cooled just enough to form the first elementary particles. The first stars didn't form until around 300,000 years later. Hope that helps!

[@Bullsleagueofbasketball]

illegalr sweaters hurt illegal hoodies

[@richardsharp8276]

The universe must be full full to the power of full of life.

[@verafleck]

If just one of these formulae is wrong, all crumbles down.

[@metalwellington]

o be a fine trans non binary fluid pregnant manequin . great vid btw

[@mortkebab2849]

Olinto De Pretto came up with E=mc2 in 1903, and not the plagiarist, Albert Kikestein.

[@Bullsleagueofbasketball]

no medical help

[@cluckeryduckery261]

I don't know why it bothers me so much when people say "the universe" instead of "the observable universe." I know exactly what the presenter meant. I think just about everyone knows it's just shorthand. But it still drives me bonkers. Maybe because I feel like it's somewhat limiting, suggesting that our presumably tiny little 46 billion light year radius bubble is all that there is.

[@LaunchPadAstronomy]

Well, all we can say for sure is this is how stars work in the observable universe. Whether or not it truly works everywhere beyond is speculative at best :)

[@gentrywinn]

At about 6.5 minutes into the video he talks about radiation pressure and gravity balancing (hydrostatic equilibrium). A gaseous star model defies the established laws of thermodynamics, one of which is that a system cannot do work upon itself (self-gravitational collapse). Also, radiation is produced to reach equilibrium with the outside environment; you cannot invoke internal radiation to achieve equilibrium. Also, at about 9.5 minutes into the video he talks about the solar spectrum and temperature. Determining the temperature of an object by its thermal spectrum is only valid for true black bodies in thermal equilibrium. The Sun is not in thermal equilibrium as is evident by the convection currents.

[@Bullsleagueofbasketball]

force to baby sit is fine although i guess you donthave to be the creator of youtube maybe just facenook..popcorn ceiling

[@ridlespriger2120]

Put everbody in my PRISON just to make sure.?

[@radioboyintj]

I wish our sun was a hotter star Like blazing Sirius or Rigel

[@wolvolad25]

Numerous adds and sponsors

[@ridlespriger2120]

24 hour nickel crew

[@valsarff6525]

We can surmise that the standard solar gas model is incorrect because we cannot reproduce and test it. To do so would involve violating too many laws of thermodynamics, meaning either those laws are incorrect or the standard solar model is incorrect. However, the SAFIRE Project has electrically satisfied ALL solar observed requirements. Finally, the "elegance" between luminosity, radius and temperature is problematic, since it violates the 4th law of thermodynamics. Yes, the 4th law.