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Re: Astronomy C

Posted: September 12th, 2018, 5:49 am
by MAAAAC
I have the same issue. The closest things I've found thus far is this: http://astrosun2.astro.cornell.edu/~mas ... ces/tf.htm, but it hasn't been super useful.
I haven't had time to do it yet, but I was planning on looking into calibrating it using the milky way, to at least get a rough idea.
Ok, we're going to do this! So if we assume that those equations on the Cornell site are calibrated correctly for their respective bands (which I think is a pretty safe assumption, considering the credibility of the source and that they purportedly took the equations directly from Tully and Fisher?) then we have corrected equations that need 2 more things to be usable: input and output units and conversions to more useful quantities (ie. absolute magnitude in the B band isn't that useful, but it would be nice if we could have an equation for visual absolute magnitude or luminosity). From what I have seen through speed-reading random google-search results, the WR units ("rotationa rate for the galaxy") is the same thing as the "rotational velocity" (please correct me if I am wrong) which is typically in units of Km/s and can be found by taking half the measure of the difference in velocity between the two peaks of an H I 21 cm line graph. For the output units, well, its just absolute magnitude corrected for a band so it doesn't have "units" so we're all good there. Next is the matter of making the output values useful. I've hardly ever seen any questions ask for absolute magnitude corrected for the B band, etc. so, unless the test writers are super nice, it probably won't be that helpful. A more useful unit would be something like absolute magnitude in the visual band (which is your typical, normal "absolute magnitude") or Luminosity. This part is harder... and I don't know if it is even possible considering what the bands represent and their discrepancies for different types of stars, etc. From what I have read (https://en.wikipedia.org/wiki/Bolometric_correction, https://www.astro.umd.edu/~ssm/ASTR620/mags.html) It is possible to correct a band magnitude to convert it into bolometric magnitude (and thus, back into visual magnitude) for specific types of stars, but this wouldn't work for galaxies (unless you did something like change the bolometric corrections using the percentages of different stars in a galaxy, etc.) Perhaps it is a lost cause, and what we really need is a TF equation for the visual band or something bolometric. It's weird that we haven't been able to find one of these, as, being the most useful, you would think it would be the first equation to be created...
Actually, radio would be the most useful, since the Tully-Fischer relationship is really useful at distances where the redshift is enormous.
Yeah, I realized that shortly after posting this... But does this mean we're good?? If these are indeed calibrated equations with useful and known input and output values, we should be able to use them, right? Is there a problem with these equations that I'm not seeing?

Re: Astronomy C

Posted: September 14th, 2018, 7:19 pm
by bmd234
Hi, I've never done Astronomy before but have done many binder events in the past. I was wondering how Astronomy binders are supposed to be set up typically, because Astronomy isn't like Herpetology, Fossils, Invasives, or any events that you can really list what you need under each DSO and fill it in as far as I'm concerned. My idea of what's supposed to be done is probably to make general pages for the part in the manual where it lists Stellar evolution, including stellar classification, spectral features and chemical composition, luminosity, blackbody radiation... etc, and then put in pictures of each DSO. My only problem is I'm not really sure if that's the best way to make the binder. Would anybody be able to give me an example or a general idea? That would be super helpful, thanks. :D

Re: Astronomy C

Posted: September 15th, 2018, 7:05 am
by Unome
Hi, I've never done Astronomy before but have done many binder events in the past. I was wondering how Astronomy binders are supposed to be set up typically, because Astronomy isn't like Herpetology, Fossils, Invasives, or any events that you can really list what you need under each DSO and fill it in as far as I'm concerned. My idea of what's supposed to be done is probably to make general pages for the part in the manual where it lists Stellar evolution, including stellar classification, spectral features and chemical composition, luminosity, blackbody radiation... etc, and then put in pictures of each DSO. My only problem is I'm not really sure if that's the best way to make the binder. Would anybody be able to give me an example or a general idea? That would be super helpful, thanks. :D
The DSO section can be treated like an ID event. For math, a good formula sheet and list of useful constants will suffice (I recommend making your own for these). Conceptual topics - you would want to memorize the general overview, keep sections on various important topics (low-mass vs. high-mass stellar evolution, relevant types of variable stars for this year, important stages in stellar evolution, galactic structure, starburst galaxies, etc.), and then have a bunch of reference tables - stellar properties by Harvard and Yerkes class, important spectral lines, etc.

Re: Astronomy C

Posted: September 17th, 2018, 2:57 pm
by bearasauras
Hey guys, I've been working on the DSO list this year and I've got a clarification question. DSO vi. on the list is SN2014, but there are 136 CBAT supernovae using that designation. I think the rules intend SN2014J, which was the brightest supernova of the year, but it doesn't specify.

If any of y'all know anything I'd appreciate it a ton
I think it's supposed to be SN 2014J; "SN 2014" is a typo.

(usual disclaimer: this is not an official clarification)
Clarification has been posted correcting this:
Astronomy - 9/17/18 (Division C) 3.c.vi. should read, edits in bold: SN2014J (was missing the J)

Re: Astronomy C

Posted: September 23rd, 2018, 1:02 pm
by alchzh
I'm having a bit of trouble with notes on "galactic structure and interactions". What kind of knowledge on this do you think would be expected?

Re: Astronomy C

Posted: September 23rd, 2018, 6:25 pm
by syo_astro
I'm having a bit of trouble with notes on "galactic structure and interactions". What kind of knowledge on this do you think would be expected?
A similar question applies to most of the rules, so it helps to narrow in on what's the issue (even if it's just "where to begin"). Is there anything specific you're having trouble with (e.g. is the issue more with "structure" or "interactions)? Are you confused what to search? Or is it more practical, like are you unsure what questions could be asked on a test based on what you've searched (not the only approach to starting studying...but still a fair question)?

Re: Astronomy C

Posted: September 23rd, 2018, 7:39 pm
by alchzh
I'm having a bit of trouble with notes on "galactic structure and interactions". What kind of knowledge on this do you think would be expected?
A similar question applies to most of the rules, so it helps to narrow in on what's the issue (even if it's just "where to begin"). Is there anything specific you're having trouble with (e.g. is the issue more with "structure" or "interactions)? Are you confused what to search? Or is it more practical, like are you unsure what questions could be asked on a test based on what you've searched (not the only approach to starting studying...but still a fair question)?
Lazily copied from IRC
22:37 <alchzh> syo_astro: I'm just not sure what they want for galaxial interactions other than "things happen" and "ask the physics models" lol
22:37 <alchzh> and to a lesser extent what all there is to be learned as a high schooler regarding structure
Regarding interactions: is this just going to be a case by case thing regarding the specific DSOs we have?

EDIT: Might we need to know advance physics-y stuff like http://casa.colorado.edu/~danforth/scie ... ION0001000 ?

Re: Astronomy C

Posted: September 23rd, 2018, 8:16 pm
by OrigamiPlanet
I'm having a bit of trouble with notes on "galactic structure and interactions". What kind of knowledge on this do you think would be expected?
A similar question applies to most of the rules, so it helps to narrow in on what's the issue (even if it's just "where to begin"). Is there anything specific you're having trouble with (e.g. is the issue more with "structure" or "interactions)? Are you confused what to search? Or is it more practical, like are you unsure what questions could be asked on a test based on what you've searched (not the only approach to starting studying...but still a fair question)?
Lazily copied from IRC
22:37 <alchzh> syo_astro: I'm just not sure what they want for galaxial interactions other than "things happen" and "ask the physics models" lol
22:37 <alchzh> and to a lesser extent what all there is to be learned as a high schooler regarding structure
Regarding interactions: is this just going to be a case by case thing regarding the specific DSOs we have?

EDIT: Might we need to know advance physics-y stuff like http://casa.colorado.edu/~danforth/scie ... ION0001000 ?
It may very much be so if this is a binder/computer event; I would look into specifics of each object, especially if it is a galaxy and potential stars they may have (take this with a grain of salt though!)

Re: Astronomy C

Posted: September 23rd, 2018, 8:24 pm
by alchzh
It may very much be so if this is a binder/computer event
I can confirm that this is indeed a binder/computer event

welcome to Div. C?

Re: Astronomy C

Posted: September 23rd, 2018, 8:27 pm
by OrigamiPlanet
It may very much be so if this is a binder/computer event
I can confirm that this is indeed a binder/computer event

welcome to Div. C?
Thanks, still trying to adjust to astronomy after reach for the stars had been replaced by solar system last year. Not doing so hot right now :cry: