Astronomy - Ch. 17: The Nature of Stars (22 of 37) Stellar Classification: Spectral Class

[@0219-n1e]

I think the astronomy has just started . Thanks a lot Professor.

[@ekaterinastrieby6432]

Great! Your videos are so nice, Michael van Biezen!

[@walkreadsleep3165]

Very Nice. From days of school I remember the spectral classes because there was a funny mnemonic, very helpful for exams. Those days are long gone and I suspect any such mnemonic must have been updated, as the one we knew was just a teensy bit male chauvinist. :) This old man has become interested in inertial frame dragging -- especially near very massive rapidly rotating stars. I came across the idea in Zee's book on GR/Astro where he outlines, in one of the comments or exercises, how efficiently and prodigiously these rotating objects can generate energy. I was stunned at the numbers -- and thought 'what about inertial frame dragging?' He discusses IFD elsewhere, but not in this context, as far as I know. But more generally perplexed I became as I realized (faulty memory or didn't study sufficiently -- or both!) that ever since the excitement with neutron stars in the 1960's --which Y. B. Zel'dovich discussed so marvelously (US students in GR were very fortunate to have translations!) -- never did I hear of an astrophysicist who said: "so heavy, and at such rotation rates!? -- what's the situation with Inertial Frame Dragging here??" I enjoy your lectures, especially fundamental mechanics. If only there were more physics teachers of your patience and ability.

[@MichelvanBiezen]

That male chauvenist mnemonic is still very much in vogue (due to the lack of a better one) Inertial frame dragging is also very much in vogue and lots of research is ongoing to measure and determine the effects and it has been measured and verified in a number of experimental measurements. Neutron start should certainly cause IFD.

[@walkreadsleep3165]

Michel van Biezen If, and only if, you can recommend a source on recent investigations into IFD in contexts of neutron stars and other very massive rotating objects it would be of great interest to me, as your appraisal impresses me as worthy recommendation. I have some access to journals. Only if you have some at hand. Otherwise, when times allows I will commence searching. Am I very much mistaken in regarding IFD in those contexts as being possibly ripe with revelations as profound as Planck's and Einstein's in their time? Thank you.

[@MichelvanBiezen]

WalkReadSleep The trick is to find material that is written is such a way that we can understand it. What I do is read as many sources that I can find and then cross reference them in order to pull out the information I am looking for. There are not very many authors who are good at explaining things in a way that I can make sense out of it, and reading the same topic multiple times by different authors helps me to put the pieces together.

[@javierbiaggi3072]

Btavo!