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Distance of stars 
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#1
Nov1203, 09:02 AM

P: 10

please can somebody help me with this parallax equation:
D=distance to star theta=angle using the rule D=(d/2)/tan(theta/2) when d = 300*10tothe6 and theta = 5*10tothe5 what is the distance to the star in km and light years? 


#2
Nov1203, 09:19 AM

P: 27

Okay  assuming that you've given the units in kilometres and degrees...
To get the answers in km you should just be able to plug the numbers into a calculator. To get the answer in light years you have to first calculate how far a light year is (in km, obviously). Rather than me just giving you the answer, why don't you have a go, then we can see if our answers agree... Jess 


#3
Nov1203, 09:32 AM

P: 10

hi there thankyou for your interest in my posting jess
d is in km theta is in degrees 


#4
Nov1203, 09:36 AM

P: 27

Distance of stars
You'll be wanting to hit 'post reply' rather than 'new thread', then
Oooh look  we've been moved Jess 


#6
Nov1203, 10:53 AM

P: 10

for this answer i get a result of:
343774677078406.6587981892079753 So, is this answer the number of km? what is this answer in exponential form? ie: 34 * 10tothepower13? 1 light year is 9.467*10tothepower12, so in light years i think the distance will be: 27 light years Please let me know if i am right 


#7
Nov1203, 11:14 AM

P: 27

Yes, that's the answer in kilometres, and it's the same one that I've got.
34 x 10^13 km is correct as well. If you take the speed of light to be 300,000 km/s, then a light year is 9.461 x 10^12 km  which looks roughly like what you put. I get an answer of 36.3 l.y though  you might have typed a digit wrong somewhere, perhaps. Even a backoftheenvelope type calculation gives an answer of at least 34, if you look closely. Jess 


#8
Nov1203, 11:17 AM

P: 10

thankyou very much jess!
I need the help for some uni coursework. p.s. I am from edinburgh too! 


#9
Nov1203, 11:20 AM

P: 27

This isn't Astronomy 1Ah or 1Ch work, is it?



#10
Nov1203, 11:28 AM

P: 10

i study at the university of abertay dundee and travel from edinburgh.
My coursework is from "horizons of science 1". this module is concerned with the big bang, black holes, telecommunications and cosmological phenomena 


#11
Nov1203, 11:32 AM

P: 27

Hehe  for a moment there I thought you might be one of my tutees (if that's the right word)
Good luck with the rest of your course... Jess 


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