Astronomy C

[celtics09]

What resources did u guys use at state? If at all possible, could u guys send me the resources?

thanks,
celtics09

[pjgscioisamazing]

Also, there was a multiple choice question about our local group and the choices were that its:

A) An irregular group within a supercluster
B) A regular group within a supercluster
C) An irregular group not in a supercluster
D) A regular group not in a supercluster

OR something to that effect

I know that we are in a supercluster (Virgo Supercluster), but I don't know if our group is irregular or regular... Anyone know out there?

Well, it's shaped like a dog bone or a dumbbell. My guess, that would count as irregular.

What did you think of the test overall?

I thought it was a very good test... I focus on DSO's/Galaxy/THings of that nature, while my partner focuses on Math/Physics, and I thought the questions were pretty easy. I did like the graphing and charting we had to do though, although I had to double check my "HR" graph cause of the logarithmic scale My partner said a few math questions were weird..

Overall, good test, good questions.

[JustDroobles]

The rules say we may have to analyze light curves... can anyone give me an example of that would look like, and what kind of questions would go along with it?

[pjgscioisamazing]

The rules say we may have to analyze light curves... can anyone give me an example of that would look like, and what kind of questions would go along with it?

I would think one question would be to ID what kind of variable star a certain light curve is for. Also, I've seen a question asking about the light curve of Epsilon Aurigae at every competition I've been at so far (Invitationals, Regionals, and States). they gave the picture of the light curve and asked which object it is (Epsilon Aurigae)

[JustDroobles]

The spectral lines of two stars in a particular eclipsing binary system shift back and forth with a period of 8.00 months. The lines of both stars shift by equal amounts, and the amount of the Doppler shift indicates that each star has an orbital speed of 9.00×10^4. What are the masses of the two stars? Assume that each of the two stars traces a circular orbit around their center of mass.

How would you solve this?

[walkingstyx]

The spectral lines of two stars in a particular eclipsing binary system shift back and forth with a period of 8.00 months. The lines of both stars shift by equal amounts, and the amount of the Doppler shift indicates that each star has an orbital speed of 9.00×10^4. What are the masses of the two stars? Assume that each of the two stars traces a circular orbit around their center of mass.

How would you solve this?

Just use Kepler's Third Law.
m1+m2=t^2/a^3.
They give you the period in the first part (3/4 years), and with the period and the speed, you can find out the distance the stars travel (d=vt). Once you know that they are orbiting in circles, you can see that the distance in the circumference, and use that to find out the average separation of the stars. Now you have both t and a. By the fact that both stars are going the same speed, you can tell that they are the same mass, so you have all of the parts of the equation. Just make sure that your units are in years, solar masses, and AU.

[Suzumebachi]

Had States competition... and didn't know a thing about Supernovae, so therefore, I failed at the first 3 pages. Out of 5. But still scraped a 5th place, saved by downloading a lot of wikipedia pages onto my computer

My partner conveniently broke his hand the day before

[pjgscioisamazing]

Had States competition... and didn't know a thing about Supernovae, so therefore, I failed at the first 3 pages. Out of 5. But still scraped a 5th place, saved by downloading a lot of wikipedia pages onto my computer

My partner conveniently broke his hand the day before

What did they ask about Supernovae?

[sunjayc99]

I've been having a bit of trouble trying to find a value of Hubble's constant to use for equations since all of the values I've found are estimates.
Would I be better off just asking the proctor what value they used before the test?
Also, how would one use the constant to determine the age of the universe (in years)?

[manutd94]

I've been having a bit of trouble trying to find a value of Hubble's constant to use for equations since all of the values I've found are estimates.
Would I be better off just asking the proctor what value they used before the test?
Also, how would one use the constant to determine the age of the universe (in years)?

The value of 65 km/s/mpc is most commonly used (as the Hubble constant). However, values may differ between 50 and 80 km/s/mpc depending on the proctor, so it is best to ask for clarification before the test. As for the age of the universe, if you know hubble's law stating: v = H * d, you can rewrite it so that 1/H = d/v. d/v is equivalent to t (time), so you would go from there and convert as needed to years.