Calculating Transverse Velocity of a Star

AI Thread Summary
To calculate the transverse velocity of a star with a proper motion of 0.249 arcsec/yr at a distance of 23.8 parsecs, the formula vt = d x sin(mu) is appropriate. The discussion highlights the importance of using consistent units, suggesting options like meters, kilometers, or astronomical units (AU). A right triangle can be used to visualize the calculation, where the distance moved by the star in a year can be derived using trigonometry. There is uncertainty about the correct units to use, with a recommendation to consider AU for the calculations. Accurate unit selection is crucial for obtaining the correct result in this context.
grscott_2000
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Hi, I've been asked to find the transverse velocity of a star. It has a proper motion of 0.249 arcsec/yr and it is at a distance of 23.8 parsecs.

Now I am happy with the formula to use (vt = d x sin(mu)) but I am not sure of the units I am supposed to be using. I've plugged these values straigh in but the result doesn't seem correct.

Can anyone perhaps tell me what units are supposed to be used here?

Regards
 
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1 Parsec = 3.086 × 10^16 meters

Make a right triangle with one angle of 0 degrees, 0 minutes, and 0.249 seconds (0.249"). The length of hypotenuse will be essential the same as the length of the adjacent side, so it doesn't matter which one you choose to be the distance to the star (oh, meters or km works fine). Do a little trig to find the distance the star moves in a year.

Units could be m/s, km/year, m/year.
 
… Au … ?

grscott_2000 said:
im not sure of the units I am supposed to be using. I've plugged these values straigh in but the result doesn't seem correct.

Can anyone perhaps tell me what units are supposed to be used here?

Hi grscott_2000! :smile:

I suspect you're supposed to do it in AU (astronomical units) … see:

http://en.wikipedia.org/wiki/Parsec#Calculating_the_value_of_a_parsec
 
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