- #1

Mohammed_I

- 8

- 0

^{-3}arc seconds.

Taking the distance between the sun and the galactic center to be 24,136 light years, and assuming the sun orbits it at a tangential velocity of 220 km/s. That is a total angular movement of 0.31 arc seconds over a 50 year period, easily measurable I assume.

However, if you try to apply the same method to measure the velocity of a star in say the Triangulum Galaxy, it doesn't seem possible. Let's say the distance between us and the galaxy is 2.725x10

^{6}light years, and we are trying to measure the velocity of a star 35 arc minutes away from the center (that is 27,744 light years away). And let's also say that this star is orbiting at a tangential velocity of 200 km/s. That is a total displacement of approximately 0.03 light years over a 50 year period, or if we convert it to angular movement from our perspective, 2.52x10

^{-3}arc seconds over a 50 year period.

So do we have a telescope with this resolution that has been around for 50 years? And even if that is the case, what do we do with galaxies that are further away?