Page 10 of 15
Re: Astronomy C
Posted: February 14th, 2016, 2:24 pm
by sciolymom
FuzzyLogic wrote:Just went to regionals. After spending hours on my binder they used last year's test! It was about variables and didn't have a single question about the DSO's! We were pretty frustrated.
I'm not sure some of the math questions were even possible. One question gave us the radius of an exoplanet and the distance from its star but not the luminosity of the star. Correct me if I'm wrong, but I don't think that's possible. At this point we just wrote down "well, this problem requires the luminosity of the star to be answered. Unfortunately it was not provided." The next question asked if the planet was habitable. We wrote "perhaps."
But hey,we got second! I think everyone else was just as clueless. The team that won actually didn't study. They just used last year's binder. Probably the only time not studying pays off.
I am so sorry that happened to you! (Not the second place, but the test.) I think it is very sad when event supervisors/tournament directors don't take the time to make sure the test is current. People are working so hard, it's just like a slap in the face to have that happen. We had a couple of years where there were a few of those, last year seemed to be better, so we are hopeful for this year.
ANDREWWSKI, thank you for your explanation above. I reviewed it with my students, who actually understand the math better than I do at this point, and we all translated it together.
(edited to thank the appropriate person!)
Re: Astronomy C
Posted: February 14th, 2016, 3:39 pm
by syo_astro
Oh, I'm not sure if I had made an explanation yet, maybe you are talking about Andrewwski's very good and detailed one? Either way, glad you figured out what you were having issues with.
Re: Astronomy C
Posted: February 15th, 2016, 11:13 am
by FuzzyLogic
They asked us for the surface temp of a planet .95 ly away from its star. We were given the radius of 1000 km. Correct me if I'm wrong, but that's not possible? I would assume that you need to know the luminosity of the star. That planet would be a lot hotter if the star is a superluminous blue giant than if it were a red dwarf.
Re: Astronomy C
Posted: February 15th, 2016, 2:44 pm
by sciolymom
syo_astro wrote:Oh, I'm not sure if I had made an explanation yet, maybe you are talking about Andrewwski's very good and detailed one? Either way, glad you figured out what you were having issues with.
Your're right! I'm used to you having all the answers...
Andrewwski, my apologies and thanks!
Re: Astronomy C
Posted: February 15th, 2016, 6:43 pm
by syo_astro
FuzzyLogic wrote:They asked us for the surface temp of a planet .95 ly away from its star. We were given the radius of 1000 km. Correct me if I'm wrong, but that's not possible? I would assume that you need to know the luminosity of the star. That planet would be a lot hotter if the star is a superluminous blue giant than if it were a red dwarf.
Yeah...you probably need one of luminosity, temperature, or intensity in some form for that. I would hope it was implied in the problem...at least you seem to know what the problem entails, so that's good for future competitions/interest in exoplanets!
Re: Astronomy C
Posted: February 19th, 2016, 1:50 pm
by sciolymom
Regarding HR 8799, the webinar slides say this system has 5 planets, but I'm only seeing info that says 4 planets. Is 4 correct, or am I missing a planet somewhere?
Re: Astronomy C
Posted: February 23rd, 2016, 10:43 am
by tad_k_22
sciolymom wrote:Regarding HR 8799, the webinar slides say this system has 5 planets, but I'm only seeing info that says 4 planets. Is 4 correct, or am I missing a planet somewhere?
That's an error, there are indeed only 4 planets (discovered to date) in the system.
Re: Astronomy C
Posted: February 26th, 2016, 3:28 pm
by sciolymom
Thank you for the confirmation, Tad! The info on astronomy sometimes changes so quickly, I just wanted to be sure.
Separate question: When you are given a radial velocity graph that only has phase across the bottom, how do you determine the period? The phase is a portion of the period, right? But how would you determine what the actual period is in units of time?
Re: Astronomy C
Posted: March 1st, 2016, 10:10 am
by tad_k_22
sciolymom wrote:
Separate question: When you are given a radial velocity graph that only has phase across the bottom, how do you determine the period? The phase is a portion of the period, right? But how would you determine what the actual period is in units of time?
There would have to be other information given. For example, if you have the graph of radial velocity vs. phase, and are given the mass ratio between the planet and star, one can then figure out the velocity of the planet and thereby the period for a orbit with a given eccentricity (which is normally assumed zero in SciOly problems) and semi-major axis. This comes from both the conservation of angular momentum (i.e., m_2/m_1 = v_1/v_2) and circular motion (v=2*pi*r/T).
Re: Astronomy C
Posted: March 3rd, 2016, 7:41 pm
by Magikarpmaster629
The way I understand color-color diagrams is that they compare the fluxes of different wavelengths in the form of a graph. If that's the case, then why can't we just use the blackbody curve, which gives us fluxes at all wavelengths?