Stellar Physics 1a: Star Formation

Stellar formation from a collapsing dust cloud. This is the first video in the Stellar Physics series.
#stars #astronomy #physicshelp
In this video I go over:
- Summary of what will be covered in the Stellar Physics series.
- What is a star?
- The Jeans instability (Jeans mass and Jeans length).
- The Virial Theorem
- Maximum and minimum star masses

00:00 Stellar Physics Series Overview
01:48 What is a Star?
03:28 Star Formation/Jeans Instability
08:25 Speed of Sound
10:10 Virial Theorem
12:23 Minimum Star Mass
16:02 Maximum Star Mass

[johnfrancis]

Just a heavy equipment mechanic here and really have no understanding of the math but I was just so amazed that I watched the whole video.

[cookpeecesendshiscongrats]

Very nice! Thank you very much. Although I wished to see a derivation of the virial theorem, the quality of video is really good! Wish you more subs and views, don't give up.

[ZSiegfried]

This is an excellent series… thank you for doing it

[tomburau]

Thanks for the videos, they are very helpful! I love watching them on my daily walks!

[vkoptchev]

Initially got confused by the -GMm/r, since this is not the potential energy of a particle within the cloud. You later made it clear that the entire cloud is collapsing and our particle is always at the edge, thus feeling the entire mass of the cloud, but it could have been stated more clearly at the beginning.

[edweinb]

Very nice. Had to watch twice. So once fusion starts, the radiation pressure will cause expansion upward toward the surface. Force of gravity will increase as it goes up toward the surface until either it achieves an equilibrium between radiation pressure and gravity, or it reaches the surface and the star self-destructs. (This is NOT a super nova!)

[learnwithisaac]

You were the only one that could finally yeach me nuclear fusion

[chrisraper]

This was great! One addendum I would like to see is how the minimum temperature for fusion relates to the charge repulsion force between nuclei.

[alangraham]

Just a note that ħ is the reduced Plancks constant. Not the constant itself.

[tomaffatigato]

What do you mean when you say "the cloud will go unstable if the sound crossing time is greater than the free fall time"? When determining the free fall time, why are you using kinetic and potential energies? I am assuming that the kinetic energy of the gas is working against gravitational potential. Is that correct? If you don't mind me saying it would be nice if a few additional moments were given to explaining how and why specific equations are being used. Good to see a series of this kind, as there really isn't much of this on You Tube.

[yiyang]

Thank you so much for such phenomenal lecture series!!
Just one minor thing which I might be wrong: at 16:00, when you solve for T, would the coefficient to be:
`4/3 me G^2', instead of
`12 me G^2'?

[starstuff]

Wouldn't the outward pressure counteracting gravity be the gas pressure rather than radiation pressure?

[amedbes]

Great videos, thank you so much!
Just one question: how did you achieve this quality in your videos (hardware and software)?

[thomasaffatigato]

Can't particle bump onto other particles faster than the speed of sound?

[personthewat]

So wouldn't a higher temperature allow for an even smaller mass? I guess the smallest mass possible would be a single instance of 4 H fusing into He if T is hot enough to not be a limiting factor. So what would the minimum mass be if we wanted to create the smallest star possible which brings into question what mass is required to define a star and not an arbitrary fusion reaction?

[darthvader]

Can you make a video about some book recommendations on stellar physics ? Such as star formation, star collapse I mean on the topics you talk about ?