How do I convert kilometers per second into parsec per year?

Question

I've worked out that a given galaxy is traveling at an apparent speed of 1.47x10^(4) km s^(-1) and I know that 1.0 parsec is roughly equal to 3.1x10^(13) but I'm completely blank as to how I now convert the speed from km s^(-1) to pc y^(-1).

any help would be hugely appreciated!

Answer 1

I just answered this question in another. Please do not multipost.



I will cut and paste my solution from the other forum.



1 Parsec = 3.1 × 10^16 meters (not 10^13) That would put you off by a factor of 1000 ;) To make life easier, please write it as km /s not km s^(-1)



I typed "1 km/s = ? pc / yr" into google and got:

1 (km / s) = 1.02268944 × 10-6 pc / yr



so just multiply that by 1.47x10^4 :)



Let's see if that makes sense using the numbers you provided (with the correction)



Standard conversions (always multiply by 1 while units cancel out, just like chem class) For clarity I have annotated the "current" units off to the right, since the more conventional "across the board or paper" method doesn't work here in a text area



1.47x10^(4) km / s (km / s)

* 1000 m / 1 km ( m / s)

* 31556926 s / 1 yr (m / y)

* 1 pc / 3.1x10^16 m (pc / yr)

= 0.015 pc / yr (approx)



or using the google calculator directly



14700 (km / s) = 0.0150335347 pc / yr



Use the automated tool to double check your work (you would have noticed the off by factor of 1000) But not exclusively until you understand basic conversions.

Answer 2

Parsec To Km

Answer 3

first convert the speed in km/s to km/yr



seconds in a day = 24 hours x 60 minutes x 60 seconds = 86,400 seconds



now multiply,



1.47 x 10^4 x 365 days x 86,400 seconds = 4.635792 x 10^11 km/year



now convert the kilometer to parsec



1 parsec = 3.086 × 10^13 kilometers



so, 4.635792 x 10^11 /3.086 × 10^13



= 0.015023579 parsec



on rounding we get,



1.5024 x 10^ -2 parsec/year

Answer 4

1 kilometer / second = 1.02268944 × 10-6 Parsecs / year



make it a good day

Answer 5

You can't, one is a measurement of speed the other is one of distance.