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Thread: Interstellar Medium; current leaders, current challanges?

  1. #1
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    Interstellar Medium; current leaders, current challanges?

    Who are the current leaders, icons in this part of astronomy? What are they struggling with right now?

  2. #2
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    You are asking about a topic that is a little on the dry side... no explosions or other fast changes... so no celebrities.
    I would recommend looking at arxiv.org, and scan the astrophysics papers to see who is publishing on this topic.
    Forming opinions as we speak

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    Quote Originally Posted by tu144 View Post
    Who are the current leaders, icons in this part of astronomy? What are they struggling with right now?
    That's a bit of a broad topic, can you narrow it down a little?

    Icons take time to develop, so you have to look at a certain person's total career. Bruce Draine is a very big name in the theory of interstellar dust. Ed Jenkins is interested in metal depletion and the distribution of thermal pressures in the cold, neutral medium. These are a couple of the big names that pop into my head without much thought.

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    I can't really narrow the field. I'm looking for someone who did something significant in this field, whatever the specific part of the field was and is more or less good expalinor like Richard Feynman and is famous enough to be interviewed at least once or gave a videolecture that I can find somewhere on the internet.

    Someone like William A. Klemperer
    form wikipedia
    (...)most widely known for: (...)(3) Pioneering Astrochemistry, including developing the first gas phase chemical models of cold molecular clouds that predicted an abundance of the molecular HCO+ molecular ion that was later confirmed by Radio Astronomy
    I've managed to find his lecture at:
    http://www.vega.org.uk/video/programme/64

    If it comes to Bruce Draine
    I've found his lecutre on: http://www.astro.princeton.edu/~drai.../lectures.html
    But if it comes to Ed Jenkins, he doesn't even exits on wikipedia.

    If someone else comes to your mind, I'd be grateful for names I can check.

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    Lyman Spitzer and Don Osterbrock were major gurus as important parts of ISM study came to maturity. Each left massive legacies of articles and books. Poking around with Google turned up this interview with Osterbrock. There are several available with Spitzer, mostly in the context of his being an early and forceful proponent of space astronomy (some date Hubble's inception to Spitzer's 1947 "white paper" appendix for the RAND corporation).

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    Yeah, Spitzer's name came up when you mentioned Feynman. Osterbrock is another great example of a pioneer in ISM. However, neither are really "current".

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    I've checked them. It's kind of odd that there are absolutly no video or audio recordings of these figures. It wasn't that long time ago, there should be something.

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    Quote Originally Posted by tu144 View Post
    I've checked them. It's kind of odd that there are absolutly no video or audio recordings of these figures. It wasn't that long time ago, there should be something.
    Why is that odd? Most astrophysicists don't become known to pop culture and there'd be little reason to record them. I'm not sure anyone outside of astronomy knows who Donald Osterbrock was.

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    Quote Originally Posted by Amber Robot View Post
    Why is that odd? Most astrophysicists don't become known to pop culture and there'd be little reason to record them. I'm not sure anyone outside of astronomy knows who Donald Osterbrock was.
    I suppose you are right on this one.
    But still if somebody is extremely good in his area and he discovered something important, you would want to at least talk with him and record the conversation.
    Maybe I'm bad in searching but even with such icon like Edwin Hubble I've only managed to find 3 seconds of archive video in italian documentary about him: http://www.youtube.com/watch?v=SM-f6...tailpage#t=64s

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    Prohibited lines of emission in ionized nebula spectrum (IM)

    Why prohibited lines of emission show up in ionized nebula spectrum?
    Why are they so bright in ionized nebulas?
    Why they don't appear in normal conditions on Earth?

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    Greetings,

    Quote Originally Posted by tu144 View Post
    Why prohibited lines of emission show up in ionized nebula spectrum?
    Why are they so bright in ionized nebulas?
    Why they don't appear in normal conditions on Earth?
    By "prohibited lines", do you mean forbidden lines? I ask explicitly because the terminology "prohibited" is not used in spectroscopy whereas "forbidden" has a well defined meaning.

    Best regards,
    EigenState

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    Interstellar dust (IM)

    What effects produce interstellar dust in the spectrum of nebulae?
    How can I quantify interstellar extinction from the nebulae spectrum?
    Last edited by tu144; 2011-May-13 at 08:03 PM.

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    Yes. I ment forbidden. Sorry for that.

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    HII regions movement (IM)

    Why gas of a nebulae is set in motion when it gets ionized?
    Why most of the HII regions we see have an expansion velocity of about 10 km / s?

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    Spectral lines of CO molecule, molecular clouds in interstellar medium (IM)

    Why are these lines so useful for studying molecular clouds?

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    Critical density of an atom level (IM)

    What is the critical density of an atom level?
    What happens to the intensity of the collisional excitation lines when it exceeds this density?

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    Empirical diagrams in context of Interstellar Medium (IM)

    What are they?
    What could be the examples of such diagram?

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    Temperature in ionized nebulae from collisional excitation lines(IM)

    How to calculate the electron temperature in ionized nebulae from the ratio of intensity of collisional excitation lines?

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    Planetary nebulae vs HII region (IM)

    What are the differences between these two?
    What are they characteristic spectrums?

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    Greetings,

    The term "forbidden" rigorously means that a specific transition is not an allowed electric dipole transition. Such transitions are allowed as either magnetic dipole or electric quadrupole transitions which are typically 106 or 108 times less probable. Thus "forbidden" transitions certainly do occur but they are weaker.

    The quantum mechanical description of photon emission can be conveniently summarized by a set of so-called selection rules which account for the changes in the various angular momentum quantum numbers describing the relevant energy levels. For just one example: the selection rule ∆S = 0 applies to electric dipole transitions, whereas ∆S = 1, ∆S ≠ 0 applies to magnetic dipole and electric quadrupole transitions.

    To reiterate, there is nothing forbidden about "forbidden" transitions. They involve different kinds of quantum states with different changes in the quantum numbers. So what "forbidden" really means is that such transitions are less probable, weaker (in the sense that the transition probabilities are very much smaller), and the energy states tend to be much longer lived.

    Such emission lines show up in many situations, even here on Earth. The principle component of the night time airglow is an emission feature from OI at 5577.34. This is an electric quadrupole (E2) transition. Such lines would be strong in the spectra of certain astronomical objects because the physical conditions within those objects selectively populate the pertinent energy levels--that is they appear strong because the transitions you are more used to do not come into play.

    Hope that helps some.

    Best regards,
    EigenState

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    Formation of molecules in interstellar medium (IM)

    What are the different processes of formation of molecules in interstellar medium?
    How H2 is formed?

  22. #22
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    tu144,

    10 new threads in an hour, all on Interstellar medium. Are you using BAUT to write your dissertation? You might want to slow it down, just a bit.

    Upon further consideration - I've merged the threads
    At night the stars put on a show for free (Carole King)

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  23. #23
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    With that many detailed questions, you might well start with tracking down a copy of a book, such as Osterbrock and Ferland's Astrophysics of Gaseous Nebulae and Active Galactic Nuclei or Spitzer's older book on the interstellar medium. Our explanations would only be distilled versions of such pedagogically ordered material.

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    Quote Originally Posted by ngc3314 View Post
    With that many detailed questions, you might well start with tracking down a copy of a book, such as Osterbrock and Ferland's Astrophysics of Gaseous Nebulae and Active Galactic Nuclei or Spitzer's older book on the interstellar medium. Our explanations would only be distilled versions of such pedagogically ordered material.
    Bravo!!

    @Swift: I believe you missed one thread. Parameter of ionization

    Best regards,
    EigenState

  25. #25
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    Quote Originally Posted by Swift View Post
    tu144,

    10 new threads in an hour, all on Interstellar medium. Are you using BAUT to write your dissertation? You might want to slow it down, just a bit.

    Upon further consideration - I've merged the threads
    Nope. I need to learn Interstellar Medium basics in 10 days. BAUT forum is the only place I used so far I can ask questions and go on with a topic until I get a thing. I was going to follow and participate in all 10 discussions I've started.
    They are only 10, there was going to be a lot more after solving these.
    Merging them will not help me.
    As you can see
    With that many detailed questions, you might well start with tracking down a copy of a book(...)
    I put them separtely so not to make total chaos and make the discussions possible.
    It would really help me if you could separate them again.
    Thank you.

  26. #26
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    Quote Originally Posted by tu144 View Post
    It would really help me if you could separate them again.
    Thank you.
    No.

    You will not dominate the Q&A section of BAUT by having half the first page of questions all yours. That's not fair to other BAUT members.

    Please use a report or PM to discuss this further, don't post in-thread.
    Measure once, cut twice. Practice makes perfect.
    Why is a frog too?

  27. #27
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    Quote Originally Posted by tu144 View Post
    Nope. I need to learn Interstellar Medium basics in 10 days.
    Just out of curiosity, why the rush? I ask because it might help motivate us too!

  28. #28
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    Quote Originally Posted by pzkpfw View Post
    No.

    You will not dominate the Q&A section of BAUT by having half the first page of questions all yours. That's not fair to other BAUT members.

    Please use a report or PM to discuss this further, don't post in-thread.
    The remaining nine would not even be answerd in this case so I don't know who to PM.
    Maybe you can tell me what is the speed limit of this forum in units of [posts/unit time(day, hour, week, whatever)],
    bring back the allowed minimum and I'll add the rest in a way not to break this speed limit?

  29. #29
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    @ the OP Tu 144; You ask a wall of questions..

    Who is leading in the fields of spectroscopic study and analysis of light emission signatures..

    Cal. tech. University and NASA and almost any astronomy branch of Universities from around the planet...

    and almost all you ask can be discussed with them. Most will respond to your inquiring mind.

  30. #30
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    Quote Originally Posted by grapes View Post
    Just out of curiosity, why the rush? I ask because it might help motivate us too!
    I want to pass 5 astrophysical subjects within 2 months one by one.
    The time for Interstellar Medium has come.

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