Expert: Jayendra Upadhye - 3/25/2005

Question
One can discount gravitational redshift caused by stars in a distant galaxy, but is a tug from its galactic core being taken into account? Perhaps a star in the Milky Way directly between Earth and our own galactic core may be falsely thought to be moving toward the core.  

Answer
Hi,
Bill!
One must never loose sight of the fact that the so called mighty pulls are but very weak ones when distances are right.
The sun's mighty "pull" if you calculate it using the inverse square law or uniform circular motion, [V*V/R = G*M/(R*R) = g(solar) where M = solar mass, R = 1 A.U. v = approx 30 km/sec earth's linear velocity in its orbit] as applied in the vicinity of the earth is 0.00something g!
Yet that is enough to lug the earth around and cause mighty tides in the oceans!

The galactic center is a might rough environment by all means.
It has a monster black hole gorging on stars in its vicinity, The huge and old globular clusters that swing up and down the galactic plain every few 10s of million years,
add to the thrilling beauty of it all.
Add to this the closely packed stars of the hub that turn in unison as a SINGLE SOLID body around that glamorous point we call the galactic center.[ref the galactic rotation curve].
No doubt gravitational lensing occurs there, but at a few 10s of light years, the inverse square law greately attenuates the "g" field to an extent where it has trivial effect on light. It is then plain old newtonian mechanics again!
So dont worry about gravitational red shifting of starlight due top the milky way center!
Jayen