Astronomy C

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XJcwolfyX
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Re: Astronomy C

Post by XJcwolfyX » November 10th, 2012, 8:12 am

*Yeah *I'm *around *here *didn't *thread (not thing!) Lol sorry for correcting you . . . .

Anyways, lol, what are the formulae we need to know for the event, and are there any websites with all of them?
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Re: Astronomy C

Post by EastStroudsburg13 » November 10th, 2012, 8:17 am

There's a formula sheet on the bottom of the Astronomy Wiki. There might be more that you will encounter as you research, but it's a good place to start.
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Re: Astronomy C

Post by desmond the moonbear » November 10th, 2012, 8:19 am

how do you get the answers to the tiebreakers?

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Re: Astronomy C

Post by EastStroudsburg13 » November 10th, 2012, 8:22 am

By knowing them beforehand. :geek:

It depends a lot on what the tiebreaker is. It can literally be anything. It doesn't even have to be astronomy-related (although ideally it would be). In order for me, or anyone else, to give you better assistance, we'd need to know the question.
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Re: Astronomy C

Post by AlphaTauri » November 10th, 2012, 9:40 am

syo_astro wrote:Now, since this hasn't been so active (hehe, AGNs), I guess I will ask a question or two (or more...). What do people have for the period-luminosity relationship for cepheid variables? I have two equations:
Mv=-2.81log(P) - (1.43 +/- 0.1)
And:
Mv=-2.43 +/- 0.12(log(P)-1) - (4.05 +/- 0.02)
Where, Mv is the absolute magnitude of the cepheid, P is period of course.
Also, I can't remember, is the relationship only for Type I cepheids? Is there one for Type II, or is it just expected to use the graphs to approximate? Does the +/- matter so much; does it just indicate variability? Sorry, I just can't totally tell from what I've been reading.
Hm, according to Wiki, the second eq is derived from HST observations of Type I Cepheids, and according to C/O the first eq is supposed to be for Type Is (calculated by HIPPARCOS), so that's good. But C/O also gives Mv = -3.53logP - 2.13 + 2.13(B-V).

I haven't really found any PLRs for Type IIs, however, according to C/O, Type IIs are about 4 times or 1.5 magnitudes fainter than Type Is, so you could just calculate it like a Type I and subtract 1.5 mags. Also, this site gives the following eqs:
Population I: Mv = -2.81 logP - 1.43
Population II: Mv = -2.81 logP + 0.15

Edit: Whoops, realized I made a major mistake. We're good now.
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Re: Astronomy C

Post by SimplyNeedLogic » November 10th, 2012, 3:31 pm

Is it true that you have to know Calculus and Physics to do Astronomy?

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Re: Astronomy C

Post by syo_astro » November 10th, 2012, 3:46 pm

SimplyNeedLogic wrote:Is it true that you have to know Calculus and Physics to do Astronomy?
Well, maybe for the career. But for what we do, the Astronomy C event, you will almost, if never (but I like to say nothing is impossible even if it's very very unlikely) need calculus. Ever. Physics helps for...a few problems? Maybe? But you certainly don't NEED it. I did the event last year, and I managed to do basically all the math between my partner and me, despite my partner being in physics.

So yeah, really if you just put in the time and work you can definitely do fine without it :). I am pretty sure others on here can confirm they did the event without being in physics or knowing calculus.
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Re: Astronomy C

Post by Luo » November 10th, 2012, 3:47 pm

SimplyNeedLogic wrote:Is it true that you have to know Calculus and Physics to do Astronomy?
I've never seen a Science Olympiad Astronomy question that requires knowledge of calculus. As for physics, you definitely need to know certain astrophysics concepts, such as Kepler's Laws and the physics behind star formation/evolution. It's not necessary to take a physics class, though, to do the event.
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Re: Astronomy C

Post by AlphaTauri » November 10th, 2012, 5:40 pm

syo_astro wrote:But for what we do, the Astronomy C event, you will almost, if never (but I like to say nothing is impossible even if it's very very unlikely) need calculus. Ever. Physics helps for...a few problems? Maybe? But you certainly don't NEED it. I did the event last year, and I managed to do basically all the math between my partner and me, despite my partner being in physics.

So yeah, really if you just put in the time and work you can definitely do fine without it :). I am pretty sure others on here can confirm they did the event without being in physics or knowing calculus.
Luo wrote:I've never seen a Science Olympiad Astronomy question that requires knowledge of calculus. As for physics, you definitely need to know certain astrophysics concepts, such as Kepler's Laws and the physics behind star formation/evolution. It's not necessary to take a physics class, though, to do the event.
SO events tend to avoid calc in general, and while there is a LOT of calc in actual astrophysics, there's really none required for the event. The physics that you encounter in astro is for the most part, completely different from what you see in physics class (with the exception of the occasional question involving things like escape velocity or Newton's Law of Universal Gravitation, but those can be easily researched online), so honestly, a physics class wouldn't help that much anyway.

I did astro for two years without having taken calc or anything beyond a very rudimentary sixth-grade physics class and I did perfectly fine, so I'm sure you'll be fine without it as well. :]
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Re: Astronomy C

Post by syo_astro » November 11th, 2012, 12:14 am

AlphaTauri wrote:
syo_astro wrote:Now, since this hasn't been so active (hehe, AGNs), I guess I will ask a question or two (or more...). What do people have for the period-luminosity relationship for cepheid variables? I have two equations:
Mv=-2.81log(P) - (1.43 +/- 0.1)
And:
Mv=-2.43 +/- 0.12(log(P)-1) - (4.05 +/- 0.02)
Where, Mv is the absolute magnitude of the cepheid, P is period of course.
Also, I can't remember, is the relationship only for Type I cepheids? Is there one for Type II, or is it just expected to use the graphs to approximate? Does the +/- matter so much; does it just indicate variability? Sorry, I just can't totally tell from what I've been reading.
Hm, according to Wiki, the second eq is derived from HST observations of Type I Cepheids, and according to C/O the first eq is supposed to be for Type Is (calculated by HIPPARCOS), so that's good. But C/O also gives Mv = -3.53logP - 2.13 + 2.13(B-V).

I haven't really found any PLRs for Type IIs, however, according to C/O, Type IIs are about 4 times or 1.5 magnitudes fainter than Type Is, so you could just calculate it like a Type I and subtract 1.5 mags. Also, this site gives the following eqs:
Population I: Mv = -2.81 logP - 1.43
Population II: Mv = -2.81 logP + 0.15

Edit: Whoops, realized I made a major mistake. We're good now.
Well, thank you very much! But hm, one question to that. You say it's magnitudes fainter, and then you say to subtract that. Did you mean add (because of our screw-y magnitude system)?

Edit: And hm, anyone think that we'll have to know the period-luminosity relationship for all sorts of cepheids since there are many types, with many relationships, with many test makers...this sounds like a bad mix XD. Guess I'll just research it anyway, but still curious. Seems like this year will be "fun" what with the mass of questions on black holes and odd objects, and the fact that DSOs I researched a month ago have already updated -_-
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