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Re: Astronomy C

Posted: May 21st, 2014, 1:13 am
by tad_k_22
The 2014 Nationals Exam is up:

I hope everyone enjoyed it!

Re: Astronomy C

Posted: June 17th, 2014, 9:31 pm
by syo_astro
HEY PEOPLE. The user above me (Tad!) has told me a hint that I can post here for the topic next year!!!!! Excitement aside, the hint is along the lines of this. The topic will be "Stellar Evolution and __", people shouldn't bother studying RR Lyrae, Cepheids, and guess I could list other things but that's the gist. Basically it's not 100% variable stars, but variable stars still can play a role. I'd personally study them (including RR Lyrae and Cepheids, why not) for fun anyway...but beside the point. Good luck, I hope everyone enjoys the summer and remember to move onward to the edge ;). Also, I hope some of the tests I'm making pop up somewhere, hope whoever gets those enjoys. Right now all I'm doing is making a test for SSSS on It's About Time, but I'll get back to astro eventually.

Re: Astronomy C

Posted: July 1st, 2014, 1:05 pm
by Unome
syo_astro wrote:
Kyaanon wrote:There was a question I ran into that didn't quite make sense to my partner or I. The question went something like this: "You locate a visual binary in the night sky that is too far for the distance to be determined with parallax. How do you determine the distance?"

No other details were provided, which game my partner and I a bit of a headache :/
Do you have to assume other things in order to solve it? It was an essay question :P
Ughhhh I hate essay questions...they're not good for the test taker or the grader >.> (well, I guess that depends on the person). I would imagine there's a few ways to do this? I would very much ask the grader if you can. I think you kind of have to make some observations here to actually get it. Of course, you have to make it under the constraints given (that is it's a visual binary and decently far away). Unfortunately or fortunately you could use a lot of ways to figure this out then? I question also whether I should assume that they meant trigonometric parallax, spectroscopic parallax...I'll try to use a method without just in case.

You could find the angular size of the system by observation. Using spectroscopy you could maybe derive a velocity graph. You could also find the temperature of each star and probably the luminosity of each star dependinggggg on the system. You could maybe use some sort of mass-luminosity relation and then find the mass of each star (I know I'm being cheap there, but they do exist and you just need to figure out the spectral class and luminosity class of the objects...if it can't be applied I could list other ways of doing this, whatever). With that, you can find the mass of the system, then I would hope you can find the period of orbit either by observation or from your velocity graph. With period and mass you can find the physical semi-major axis. With that and the observed angular size of the system, you can then use the small-angle formula to I believe get the distance to the system.

Phew, hope that helped!
I already like this event. :)