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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Comments: 36
  1. Mark Reedman

    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

  2. Val Sarff

    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.

  3. 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?

  4. Patti Broussard #arrayartist

    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!

  5. Core E

    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.

  6. James Angius

    Like what’s the flux?

  7. pauldhoff

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

  8. 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.

  9. 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?

  10. Sangram Kapre

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

  11. The Adventures of Jon & Chad

    Hey Christian, great channel man, I found you on the The YouTube 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.

  12. Locut0s

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

  13. JJ Thomas

    And he’s a Deadhead..

  14. Abhishek Wadkar

    Nice video man keep up the good work

  15. John Lamb

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

  16. James Dougan

    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

  17. victor

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

  18. James Angius

    I love that Star graph!
    Diagram**

  19. Hard Knocks Television

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

  20. James Angius

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

  21. joe dasilva

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

  22. Radio Bill

    I thought they were all horizontal or on their knees

  23. Dan5482

    Thank you for another excellent video.

  24. Don Chamberlain

    Yes, very nice summary!

  25. Sunday Aito

    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.

  26. Adrian Tee

    Awesome and so so informative! Thanks so much!!

  27. S Oliven

    When you get childs and tell them the story of twinkle, twinkle little star, don’t forget there is much stuff between and beyond the commas.

  28. Evil Norman

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

  29. Masterchief3R3

    Love you videos, i’ve always been fascinated by stars thank you for explaining

  30. pipertripp

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

  31. Martin Stallard

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

  32. Legion of Weirdos

    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 🙃

  33. aresmars2003

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

  34. The Gunman

    You’re a star 🌟

  35. Huskii

    Best video on stellar evolution and general star stuff

  36. Gleyson Oliveira

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

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