Would a galaxy's geometry appear warped?

Question

Say, we are 100,000 light/years away from a hypothetical galaxy that is 100,000 light/years in diameter.
We can see the close edge of this galaxy and the far edge of this galaxy.
Close edge is 100,000 light/years away from us. Far edge is 200,000 light/years away from us.
Since the light takes longer from the far edge to us, the galaxy's geometry shoiuld appear distorted to us?
Instead of seeing spiral arms we should see a soup a stars. Discuss.

This is important to the question... this galaxy is rotating around is center.
The stars position on the far side of this galaxy are not anywhere near their real position as we see them! The close side stars are closer to the real position as we see them!

Answer 1

There is no warping that can detected from this effect. The reason is that, while the galaxy may be 200,000 light years across, it takes a thousand times that long to undergo a rotation. This makes the 'soupiness' an irrelevant effect.

Answer 2

Neglecting ligh's bending near massive objects, what we see is not very much differnt from the shape of galaxy, though this depends on its rate of changes and rotation. It's just an optical dalay in seeing what there is. In fact, what we see on the far edge belongs to 200,000 years "before" what we see on the close edge. Now assuming the galaxy does not rotate and change very much in such a period, what will seem to us does not differ very much from what the real geometry is. Even if this assumption is not in fact a good approximation, we might still see a spiral shape while we should notice that a spiral shape is not the galaxy's real shape. A computer can then help us correct the image and find the true geometry. These corrections are usual today in cosmology. But they don't mean that we should have "seen" a soup, etc. when we actually "see" a spiral. What we see is what we see and can be a spiral.

Answer 3

So does a head-on galaxy's image trace out a corkscrew in space?

Hey, if it's about 35 million parsecs away then it's facing backwards!


This should cause about 20 minutes of arc (2/3rds of a full moon) of rotational misalignment, (which would be hard to notice (especially in a diffuse 'soupy' galaxy), unless you had some nice signs out there that say (THIS POINT OF THE GALAXY EXACTLY AT LONGITUDE 0º) (GALACTIC LONGITUDE 180º DRIVE SAFELY) (CENTRAL BLACK HOLE EXACT CENTER, DON'T FALL IN) lol

Then it'd be easy.


There is also a very slight redshift difference, (which could be measured with a spectroscope), and a slight gravitational lensing
(I don't know how much but the Sun's is 1.6 seconds of arc)

Complicated with many other problems (such as interstellar extinction and Einsteinian effects) and you have a very imperfect galaxy, if only you look close enough.

Answer 4

Standard explanation:
obviously this is not the case, cause we see a galaxy head-on having the same shape if we observe a galaxy edge-on.
while you see light distorted you see gravitational effects distorted too, so theres everything ok, with how a galaxy looks .. case closed

hypothetic explanation:
obvoiusly we observe a difference in the stars motion in the outer layers/arms of a galaxy. Scientists are clueless why this is the case and say there must be an unexplainable hughe ammount of matter involved to explain that. Observations showed, theres not enough dark regular matter, to explain that... a dilemma .. so they brew a theorethical stuff called 'dark matter' put 25% of the universe's mass to the observable and guessed 4% regular matter, to explain that, yet invisible to our way observing. Now what if exactly THIS difference in motion in fact MAKES the difference ??
is there anybody who made a simulation who cared for this difference ? i don't know of such a simulation.

my personal explanation:
i don't know.. but i think its VERY interesting

Answer 5

Yes, and no...

The light from the distant side will appear slightly warped due to the bending action caused by the mass contained in the center of that galaxy that it has to pass thru in order to reach the near side.

Einstein proved the even light is bent by massive objects. The light in the near side wouldn't appeas distorted, but the light from the distant side would appear slightly warped.

If you are looking at the galaxy from the top, rather than the side, then there would be no distortion.

Answer 6

The only distortion of the light from the far edge of the hypothetical galaxy would be from gravitational lensing. Over a distance of "only" 100,000 light years any gravitational lensing would be minimal. Also a galaxy at a distance of 100,000 light years is more a smear of diffuse light rather than a collection of individual points of starlight. The effect of gravitational lensing on such a diffuse, spread out wash of light wouldn't even be detectable by any of our apparatus.