Astronomy

[Sheogorath]

Well, it is only an invintationals.

I think I had a regional test that didn't have any back in 2007, but they usually do and should.

[eak227]

Yeah if they follow the rules like they're supposed to, then yes, the DSOs should be explicitly mentioned... but I've gone to a regionals where not only has it been the same Astronomy test for the last 3 years, but it has nothing to do with variable stars at all, let alone DSOs..

[EastStroudsburg13]

What's the fun in knowing what they are if you can't use them?? You should definitely be able to use the distance modulus very easily, and know how to interpret from a graph the distance to Cepheids.

So, in other words, it's pretty basic stuff?

[eak227]

Depends entirely on the competition and who writes the test.. at nationals the test last year was probably 40% math and some of it was very difficult, not to mention a time crunch. I really do think it depends on how well the test writers actually know the math themselves. Doesn't hurt to know how to do the hard stuff.

[binary010101]

My coach usually does the test at regionals. It's about one-third math and the rest "fill-in-the-blank", matching, and picture identification.

[EastStroudsburg13]

Depends entirely on the competition and who writes the test.. at nationals the test last year was probably 40% math and some of it was very difficult, not to mention a time crunch. I really do think it depends on how well the test writers actually know the math themselves. Doesn't hurt to know how to do the hard stuff.

Would the "hard stuff" include doing the comoving distance? The formula looks like it involves calculus.

[celtics09]

On Regionals, I faced a weird question that asked me about the Stefan-Boltzmann law and Wien's law and i blanked out.
Can anyone help me understand these equations.

[eak227]

Ok... so stars obviously radiate energy. They do this via photons of varying wavelengths (Xray, visible, IR, etc). How much of each type they emit is predicted because stars act relatively close to blackbodies. So they emit energy over the entire spectrum of wavelenghts, in a form much like this.



Notice two things from the emission of blackbodies (stars). The total amount of energy released is given by the area under the curve. Also, as the total energy increases, while it emits more at all wavelengths, the peak shifts to the left.

This peak can be predicted, and is given by Wien's law, which says that the temperature of the blackbody multiplied by it's peak wavelength equals a constant, or . b depends on the units you choose for wavelength... you can find it on the Internet.

Now, the Stefan Boltzmann law relates that temperature you just found to the flux of a star. Flux, in units, is total energy per unit time per unit area, or Joules per second per square meter. Multiply flux by the total surface area of the star to get the total energy per time, or power (Watts).

Ok, so Stefan-Boltzmann law says that the flux of a star is proportional to Temperature to the fourth, or .

is the Stefan-Boltzmann constant and also can be found on the Internet.

Hope that helps.. Ask if you're confused.

[herewegoagain365]

Makes sense...

Question: I'm new to this event (in Div. C, anyway), and I'd just like to know what the format of the test is? Sorry if this has already been answered.

[binary010101]

It depends on who writes the test. Usually, there's a fill-in-the-blank section, and then, after that, questions about pictures: "What DSO is in image Q?" or light curves: "In light curve J, is the epoch or period wrong?"