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There is a mistake in this exam (the mistake is not on the answer key, but in the exam itself). My apologies to anyone agonizing over this problem. This is from the 2014 PA state exam. The separation of the stars should be listed as 1.56E10 m.

JCicc wrote:There is a mistake in this exam (the mistake is not on the answer key, but in the exam itself). My apologies to anyone agonizing over this problem. This is from the 2014 PA state exam. The separation of the stars should be listed as 1.56E10 m.

While you're here - would you happen to know whether to use distance or half of the distance in Kepler's third law? I've seen it both ways in the past but no one I've talked to seems to have a definitive answer on this.

Unome wrote:

JCicc wrote:There is a mistake in this exam (the mistake is not on the answer key, but in the exam itself). My apologies to anyone agonizing over this problem. This is from the 2014 PA state exam. The separation of the stars should be listed as 1.56E10 m.

While you're here - would you happen to know whether to use distance or half of the distance in Kepler's third law? I've seen it both ways in the past but no one I've talked to seems to have a definitive answer on this.

Never mind I was wrong you do actually use the separation for “a.” (And not just because the answer works out, I looked it up). Ahhhhh why do I suck lol...

jonboyage wrote:

Unome wrote:

JCicc wrote:There is a mistake in this exam (the mistake is not on the answer key, but in the exam itself). My apologies to anyone agonizing over this problem. This is from the 2014 PA state exam. The separation of the stars should be listed as 1.56E10 m.

While you're here - would you happen to know whether to use distance or half of the distance in Kepler's third law? I've seen it both ways in the past but no one I've talked to seems to have a definitive answer on this.

Never mind I was wrong you do actually use the separation for “a.” (And not just because the answer works out, I looked it up). Ahhhhh why do I suck lol...

Wait so is it the distance between the stars or half the distance between the stars? Now I'm confused. I always thought it was the semi-major axis of the star's orbit. (half the distance of separation between the two.)

Alex-RCHS wrote:

jonboyage wrote:

Unome wrote: While you're here - would you happen to know whether to use distance or half of the distance in Kepler's third law? I've seen it both ways in the past but no one I've talked to seems to have a definitive answer on this.

Never mind I was wrong you do actually use the separation for “a.” (And not just because the answer works out, I looked it up). Ahhhhh why do I suck lol...

Wait so is it the distance between the stars or half the distance between the stars? Now I'm confused. I always thought it was the semi-major axis of the star's orbit. (half the distance of separation between the two.)

Isn't it the sum of the two semi-major axes of the elliptical orbits of the two stars which is just the separation?

Alex-RCHS wrote:

jonboyage wrote:

Unome wrote: While you're here - would you happen to know whether to use distance or half of the distance in Kepler's third law? I've seen it both ways in the past but no one I've talked to seems to have a definitive answer on this.

Never mind I was wrong you do actually use the separation for “a.” (And not just because the answer works out, I looked it up). Ahhhhh why do I suck lol...

Wait so is it the distance between the stars or half the distance between the stars? Now I'm confused. I always thought it was the semi-major axis of the star's orbit. (half the distance of separation between the two.)

It's the full distance between the two. Consider that the distance between each star and the barycenter in a circular orbit is already a semi-major axis.

It looks like the UT Regional tournament directors decided not to upload the tests. I've put up the astro test here: http://www.cs.utexas.edu/users/dkarkada ... 0Regional/.

As always, let me know if you have any questions or think there's an error, so I can correct it. Hope this helps! :)

dkarkada wrote:It looks like the UT Regional tournament directors decided not to upload the tests. I've put up the astro test here: http://www.cs.utexas.edu/users/dkarkada ... al%202018/.

As always, let me know if you have any questions or think there's an error, so I can correct it. Hope this helps!

I've heard amazing things about this test. I'm excited!

Hey! For those of you who have competed in astro at nationals, has JS9/DS9 software ever showed up on the test?

anna1234 wrote:Hey! For those of you who have competed in astro at nationals, has JS9/DS9 software ever showed up on the test?

It hasn't been on any nationals tests or any of the MIT tests (which are written by the national event supervisors) that I've seen.