How to measure the tangential component of velocity of receding starsor quasars?

[aniketp]

Hi all,
How to measure the tangential component of velocity of receding starsor quasars?
I ask this because i think the velocity determined by observing the red shift will give only the radial component...won't
Thnx for replying...

[Quisquis]

You can't.

[triclon]

For stars their proper motion (not just radial) can be measured a few ways. If they move fast enough, comparing images from different epochs and looking for a change in position works. Interferometry, if high enough resolution, can also be used to measure the proper motion of stars. As for Quasars, I would say with current technology it's virtually impossible as they are much much too far away.