Distance of stars

  • Thread starter radius
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  • #1
radius
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0
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*10tothe-5

what is the distance to the star in km and light years?
 

Answers and Replies

  • #2
Jess
27
0
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
 
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  • #3
radius
10
0
hi there thankyou for your interest in my posting jess

d is in km
theta is in degrees
 
  • #4
Jess
27
0
You'll be wanting to hit 'post reply' rather than 'new thread', then :wink:

Oooh look - we've been moved

Jess
 
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  • #5
quantumdude
Staff Emeritus
Science Advisor
Gold Member
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Originally posted by Jess
You'll be wanting to hit 'post reply' rather than 'new thread', then :wink:

Jess

Presto! The threads are merged.
 
  • #6
radius
10
0
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
Jess
27
0
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 back-of-the-envelope type calculation gives an answer of at least 34, if you look closely.

Jess
 
  • #8
radius
10
0
re

thankyou very much jess!
I need the help for some uni coursework.
p.s. I am from edinburgh too!
 
  • #9
Jess
27
0
This isn't Astronomy 1Ah or 1Ch work, is it?
 
  • #10
radius
10
0
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
Jess
27
0
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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