Scioly.org

AlphaTauri wrote:I also wrote this test! (syo also helped with this one.)

I think I made it a bit too difficult for a Regionals... again. Sorry.

Scored 71-74 depending on credit for ambiguous answers. This test was significantly harder than MIT.

How does #73 work? I came up with all sorts of nonsensical answers but couldn't figure out what to do to combine the orbits.

Also what's going on with #35? Pretty sure those are supernovae spectra

Unome wrote:Scored 71-74 depending on credit for ambiguous answers. This test was significantly harder than MIT.

Not every invite has to be impossible, you know :P (Honestly, I think Tad/Donna do a much better job of difficulty than I do.)

How does #73 work? I came up with all sorts of nonsensical answers but couldn't figure out what to do to combine the orbits.

Find the radii of both orbits around the center of mass via (I should have specified circular orbits), and average them to get half the major axis.

Also what's going on with #35? Pretty sure those are supernovae spectra

I derped and put the wrong image on the image sheet. ("Oh right, the spectra question. Must be this picture, right?") I'll upload a fixed version...

Edit: Fixed.

AlphaTauri wrote:

Unome wrote:Scored 71-74 depending on credit for ambiguous answers. This test was significantly harder than MIT.

Not every invite has to be impossible, you know (Honestly, I think Tad/Donna do a much better job of difficulty than I do.)

Agreed, but we also didn't need ~15% of the teams over 80%.

AlphaTauri wrote:

How does #73 work? I came up with all sorts of nonsensical answers but couldn't figure out what to do to combine the orbits.

Find the radii of both orbits around the center of mass via (I should have specified circular orbits), and average them to get half the major axis.

Oh I forgot to half it... ;-; rip 6 points

AlphaTauri wrote:

Unome wrote:Scored 71-74 depending on credit for ambiguous answers. This test was significantly harder than MIT.

Not every invite has to be impossible, you know (Honestly, I think Tad/Donna do a much better job of difficulty than I do.)

Tbh your tests are the best, period (including nats) (well besides maybe nats 2016 that one was really good) (but other than that I've learned way more from yours than any others).

Magikarpmaster629 wrote:

AlphaTauri wrote:

Unome wrote:Scored 71-74 depending on credit for ambiguous answers. This test was significantly harder than MIT.

Not every invite has to be impossible, you know (Honestly, I think Tad/Donna do a much better job of difficulty than I do.)

Tbh your tests are the best, period (including nats) (well besides maybe nats 2016 that one was really good) (but other than that I've learned way more from yours than any others).

Hm, I thought the Nationals and MIT tests were of slightly better quality, but also generally easier than this one. The use of images and interpretation that they build into their math is probably part of it - although, can't really go hard on math for a regional. On this one it did seem like there was almost nothing between questions 51-70 below mid-difficulty though.

Does anyone have the period-luminosity relationship for type II cepheids? I can only find type I.

sciolyPA wrote:Does anyone have the period-luminosity relationship for type II cepheids? I can only find type I.

Generally I just use a Type I relationship and add another 1.6 to the absolute magnitude.

AlphaTauri wrote:

Unome wrote:Scored 71-74 depending on credit for ambiguous answers. This test was significantly harder than MIT.

Not every invite has to be impossible, you know (Honestly, I think Tad/Donna do a much better job of difficulty than I do.)

How does #73 work? I came up with all sorts of nonsensical answers but couldn't figure out what to do to combine the orbits.

Find the radii of both orbits around the center of mass via (I should have specified circular orbits), and average them to get half the major axis.

Also what's going on with #35? Pretty sure those are supernovae spectra

I derped and put the wrong image on the image sheet. ("Oh right, the spectra question. Must be this picture, right?") I'll upload a fixed version...

Edit: Fixed.

LOL so I took this with my partner for practice--when we started the test, you hadn't uploaded the fixed version yet, so I was pretty confused on those questions. Later in the test I accidentally closed the window and had to reopen it, and didn't notice that the image had changed. When we were going through our answers, I looked at that question again and was so shook because the image was different, and I thought I was out of my mind because I had no idea what I'd been looking at before--then I saw the forums today :')

I thought it was a rly good test, I missed like everything because I'm bad (quote my partner: "how did you put neutron star for a question where the answer was rotational energy????") but it was really good practice, so thank you for posting it! :v

Upon reading a few papers - higher metallicity implies a dimmer Cepheid than predicted by the Leavitt relationship? I notice that a higher metallicity corresponds with a lower distance modulus, but for some reason I'm having trouble interpreting the latter.

Unome wrote:Upon reading a few papers - higher metallicity implies a dimmer Cepheid than predicted by the Leavitt relationship? I notice that a higher metallicity corresponds with a lower distance modulus, but for some reason I'm having trouble interpreting the latter.

Distance modulus is defined as m-M=mu, where m is the apparent magnitude and M is the absolute. For a given m, having a lower distance modulus implies that M is greater than expected. This makes sense with the metallicity, since a Type II Cepheid is typically 1.6 magnitudes dimmer, and thus has a greater absolute magnitude (recall that the absolute magnitude increases, as luminosity decreases).