Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Describe some basic concepts for me please?

  1. Jun 28, 2011 #1
    Sorry if this is in the wrong section, but its not really homework, just curiosity.

    I'm a high school student struggling to understand a paper given to me, and search engines don't provide good starting points unless I have a more exact search query.

    The research is on star formation, investigating factors such as ionization pressure, radiation pressure and supernovae. Now some questions..

    Could someone explain stellar output? Does it have to do with heat or luminosity, and would it have any correlation to the mass of the star?
    Could someone also explain what HII fraction would be? Does it have to do with diffuse fraction (or reflection)? I believe it is ionized hydrogen, but I'm not sure about anything else.
    Also, would anyone have a good starting point for understanding the dynamics of supernovae?
    Sharing any general knowledge on these topics would be great too!

    Thanks in advance!
  2. jcsd
  3. Jun 28, 2011 #2


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    It doesn't sound like homework. I think you are in the right general area but perhaps more precisely you want to ask this in ASTROPHYSICS. Astrophysics deals with the physics of individual stars (among other things) while Cosmology is about the overall evolution of the universe as a whole. There's not an absolute sharp division, but your questions are all about individual stars.

    Probabably by "output" you mean what is technically called the [absolute] luminosity. Basically that is the "wattage" of the star---the total amount of energy it releases per second.

    As you suggest it might, the output DOES correlate with the mass. Typically, for most of its lifetime, since the more massive a star is the more pressure in its core (where the fusion happens), the hotter and faster it "burns" in its core. So typically more fusion energy is released per second, in a more massive star.

    That enhanced power output in the core percolates out to the surface. So the more massive the star is the hotter its surface gets, and the more radiantly it glows.

    I'm not using formal technically correct language---just telling you how I think about it, in my own words.

    I hope someone with more detailed knowledge answers with specifics! There are some equations relating mass to luminosity. I don't happen to know them by heart, so hopefully some more knowledgeable person will step in. As a last resort you could try googling "wikipedia star mass luminosity" or something like that.

    Also, wikipedia is good on the different mechanisms of supernova explosion. There are different ways that supernovas happen---it's pretty interesting. Keep asking questions. :biggrin:
  4. Jun 28, 2011 #3
    That really helped a lot! thanks so much!
    Don't worry, I'll be back =D
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook