# How can we calculate velocity of an object given the distance from an object in parsecs?

If you had the distance from a celestial object, in parsecs, how would you calculate the velocity of the said object?

Edit: I'm sorry I don't have more context, the specific questions is: "A galaxy that is 10 million parsecs away will be moving at what velocity?"

• Welcome! Your question is a little short on detail. Distance alone does not control the velocity at which an object is moving. A space probe, and the planet Pluto, and an incoming comet can all be at the same distance but one will be moving away from us, one towards us, one neither towards or away. Are you perhaps asking about the expansion of the universe, rather than the movements of individual objects? Jun 7, 2019 at 7:29
• There's Hubble velocity and peculiar velocity. You can roughly calculate Hubble velocity, but not peculiar velocity. For that, you need redshift: en.wikipedia.org/wiki/Peculiar_velocity Jun 7, 2019 at 16:07

That said, if you are in the regime where Hubble flow dominates, you can do this easily. The Hubble constant is approximately $$70 km/s/Mpc$$. Just convert your distance into megaparsecs, and multiply. You end up with a velocity, which is the one you're looking for (this neglects peculiar velocity, which will affect everything in the sky).