Astronomy

Glacierguy1
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Re: Astronomy

Postby Glacierguy1 » February 17th, 2009, 8:15 pm

Thanks.

What about these ones.

15)
Star C and Star D have equal masses, luminosities, and spectral classes. They are also members of a spectroscopic binary star system that is observed to have a separation of 6.0 x 107 km and a period of 10.0 days. What is the orbital velocity of Star C (in km/s)?
16)
In the spectrum for Star C, the Hα was measured to have a wavelength of 656.5386 nm compared with a laboratory value of 656.3000 nm. What is the angle between the plane of the systems orbit and the line of sight of the observer (in degrees)?

From last years nationals test if anyone cares.



Edit: I keep getting 109 ish for 15 and I have no clue for 16 at all.















Answers: 15. 200-236 km/s
16. 50-70 degrees
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Re: Astronomy

Postby Flavorflav » February 18th, 2009, 5:55 am

On the third try I got 218 for #15, but I get 39 degrees for #16.

Hey, just noticed that 218 is double 109. You are probably just dropping a two someplace. IDK what's wrong with #16.

Glacierguy1
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Re: Astronomy

Postby Glacierguy1 » February 18th, 2009, 8:51 am

Yeah, I figured that for 15, but I have no clue where that two went.
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Re: Astronomy

Postby Flavorflav » February 18th, 2009, 2:02 pm

I think I figured out #16. I sined when I should have cosined - with cos I get 51 degrees.

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Re: Astronomy

Postby Glacierguy1 » February 18th, 2009, 5:05 pm

Please explain.
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Re: Astronomy

Postby Flavorflav » February 18th, 2009, 5:17 pm

Please explain.
You have actual V from #15, so you just find apparent V from redshift. Apparent V is going to be Vaway or Vx, so Vx/v = cos inclination. I think.

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Re: Astronomy

Postby Glacierguy1 » February 18th, 2009, 5:25 pm

How did you get #15, because I think it is just a coincidence that I was a factor of 2 off from the right answer.
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Re: Astronomy

Postby Flavorflav » February 18th, 2009, 5:39 pm

2 pi A/P

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Re: Astronomy

Postby Glacierguy1 » February 18th, 2009, 9:08 pm

Thanks...

When I first did the problem, I did it using that method, but, being spacy and such I decided to do area of the circle instead of circumference, so I got a velocity that would cause the stars to convert all of their mass into energy.
The answer of 109 that I got the other times was the recessional velocity of the star that I should have gotten for the second problem.
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Re: Astronomy

Postby Flavorflav » February 19th, 2009, 2:46 am

Thanks...

When I first did the problem, I did it using that method, but, being spacy and such I decided to do area of the circle instead of circumference, so I got a velocity that would cause the stars to convert all of their mass into energy.
The answer of 109 that I got the other times was the recessional velocity of the star that I should have gotten for the second problem.
But how would you get that? From the wavelength data in question 16?

I'm still troubled by that one, BTW. My answer for the first one is smack in the middle of the accepted range, so I'm pretty confident in it. My answer for the second one is all the way at the bottom of the accepted range, indicating I may have got lucky. I think I'm doing it right, though - what do you get for #16?


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