Astronomy C

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Re: Astronomy C

Postby syo_astro » September 10th, 2018, 6:17 pm

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)
I'm thinking (and hoping, since I've already done a bunch of work under that assumption) that's probably it. I'll report it when the rules clarifications open up October 1st and we'll see for sure.

Sidebar: The DSOs this year are way cooler and more recent than they've been the past few years.
Yes, please submit an official clarification. Otherwise, it is not official and technically can't be confirmed as true. Assumptions are bad! [That said, I actually have no clue how a letter went missing...]

Also, to be fair about DSOs...just a few years ago we had exoplanets, which obviously had a ton of recently (like, really, not 100 yrs ago) discovered objects! The "old" DSOs are cool too!
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Re: Astronomy C

Postby Unome » September 10th, 2018, 6:44 pm

I think it's supposed to be SN 2014J; "SN 2014" is a typo.

(usual disclaimer: this is not an official clarification)
I'm thinking (and hoping, since I've already done a bunch of work under that assumption) that's probably it. I'll report it when the rules clarifications open up October 1st and we'll see for sure.

Sidebar: The DSOs this year are way cooler and more recent than they've been the past few years.
Yes, please submit an official clarification. Otherwise, it is not official and technically can't be confirmed as true. Assumptions are bad! [That said, I actually have no clue how a letter went missing...]

Also, to be fair about DSOs...just a few years ago we had exoplanets, which obviously had a ton of recently (like, really, not 100 yrs ago) discovered objects! The "old" DSOs are cool too!
Alternate opinion: Half the DSOs this year are basically identical - there's only so many ways to ask about a starburst galaxy (47 Tucanae is really nice though).
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Re: Astronomy C

Postby chaoticevil42 » September 10th, 2018, 8:03 pm



Also, to be fair about DSOs...just a few years ago we had exoplanets, which obviously had a ton of recently (like, really, not 100 yrs ago) discovered objects! The "old" DSOs are cool too!
Alternate opinion: Half the DSOs this year are basically identical - there's only so many ways to ask about a starburst galaxy (47 Tucanae is really nice though).
There's just something about the DSOs this year that catches my attention more so than the supernova remnants and LBVs and such that we had last year. (Exoplanets were super cool though I forgot about that I was thinking mostly about last year)
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Re: Astronomy C

Postby MAAAAC » September 11th, 2018, 6:42 am

Anyone found any actually useful Tully-Fisher equations (or other relationships that may be used for galactic computation)? I've been searching around for a few hours and have found a lot of relationships between variables but very few actually have 1. constants from observational correction or 2. input and output units for the variables, both of which are necessary to actually use an equation for a problem on a test. The closest that I've gotten with Tully-Fisher specifically is a set of equations relating absolute magnitude of a spiral galaxy in different bands to rotational velocity with correctional coefficients and constants, but these equations don't give the units of either variable. Though, I haven't spent as much time searching for other equations based on relationships, I have run into the same problem several times. If anyone has any input, advice, or even an equation, that would be great! Thank you!
I thought exactly the same thing when I was writing a test earlier. I haven't found a calibrated formula so far.
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...

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Re: Astronomy C

Postby PM2017 » September 11th, 2018, 6:37 pm

I thought exactly the same thing when I was writing a test earlier. I haven't found a calibrated formula so far.
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.
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Re: Astronomy C

Postby MAAAAC » September 12th, 2018, 5:49 am

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?

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Re: Astronomy C

Postby bmd234 » September 14th, 2018, 7:19 pm

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

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Re: Astronomy C

Postby Unome » September 15th, 2018, 7:05 am

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.
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Re: Astronomy C

Postby bearasauras » September 17th, 2018, 2:57 pm

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)

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Re: Astronomy C

Postby alchzh » September 23rd, 2018, 1:02 pm

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?
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