Comments on: Funhouse galaxy

By: Matt B.

Matt B. — Mon, 26 Mar 2012 22:32:02 +0000

Correction for MTU (@24) re Puzzled Al (@22): While gravitational redshift is a phenomenon, it occurs when you observe something that's at a lower gravitational potential (i.e. deeper in a gravity well) than you. Since the light started at mere stars and is received by us near a mere star, there's too little difference in GP to change the wavelength anywhere near as much as the inflationary redshift, or even noticeably. The lensing really has nothing to do with that, since the light will come back "up" after going "down" into the galaxy cluster's gravity well. The frequency of a photon will change by a factor of e when the photon traverses a gravitational potential difference of c^2. That is, f1/f0 = e^(ΔGP/c^2). If we observed light from the sun at an infinite distance (so that our GP is 0), the change in frequency would be a factor of e^((-GM/r)/(c^2)) = 0.999999783 (where M and r are the mass and radius of the sun).

By: Messier Tidy Upper

Messier Tidy Upper — Fri, 10 Feb 2012 04:59:11 +0000

@20. JB of Brisbane & #21. Neil Haggath :

@Messier #17 – wasn’t that the Blue Flame (Gary Gabelich, 1973)? Blue Streak was the abortive British ICBM project.

Oops. Of course! Yes, that’s the one I meant. Sorry. (Blushes.)

(Wiki-page now linked to my name here.)

@22. Puzzled Al : Not stupid questions at all. Matt (#23) is correct though I think. There is a gravitational redshift as well as the distance-light travel time one but if my possibly unreliable (example above) memory serves, it ‘s only noticeable for supermassive objects, eg. Galactic Black Holes.

@18. don gisselbeck : Indeed although I think the challenge is too much for them – ditto on why they’d listen to him about exoplanets, meteor showers & astrophysics more generally. Science works people. Everywhere. 8)

By: Matt

Matt — Thu, 09 Feb 2012 19:40:54 +0000

The bent path of the ligh IS the shortest path to us. Spacee is distorted by the gravity of the galexy cluster. Its just that our limited ability and our constraints about thinking in Euclidean three dimensions is hard to shed, so we think of the shortest distance as what we would think of as “line of sight” in non-distorted space.

Anyway, Mother Nature is full of wonderfull things. This is pretty cool!

By: Puzzled Al

Puzzled Al — Thu, 09 Feb 2012 16:57:00 +0000

If a galaxy is lensed then the light from that galaxy must travel farther than if had made a beeline to us. Would that have an effect on the perceived wavelengths of light? Is there a lot of lensing between us and billions of light years away? If wavelengths shift, could it be that this accounts for the red shift of distant entities? If that were true, could this have implications about an expanding Universe, the Big Bang, etc? Are these really stupid questions?

By: Neil Haggath

Neil Haggath — Thu, 09 Feb 2012 12:57:18 +0000

#20 JB:
Correct.

By: JB of Brisbane

JB of Brisbane — Thu, 09 Feb 2012 11:14:06 +0000

@Messier #17 – wasn’t that the Blue Flame (Gary Gabelich, 1973)? Blue Streak was the abortive British ICBM project.

By: Paul A.

Paul A. — Thu, 09 Feb 2012 06:41:00 +0000

I wasn’t quite convinced that gravity could bend space and gravitational lensing existed until I saw this picture.

By: don gisselbeck

don gisselbeck — Thu, 09 Feb 2012 05:03:52 +0000

I’d love to see some AGW denier explain precisely why I should believe Phil on gravitational lensing but not on global warming.

By: Messier Tidy Upper

Messier Tidy Upper — Thu, 09 Feb 2012 02:37:10 +0000

Continued @ 13. Sili : I’ve tried to find that galaxy cluster’s mass but had no luck. My google-fu has failed me, alas.

Anyone else know?

@8. Acronym Jim :

Ah, so maybe the main “easter egg” in Holbein’s painting, “The Ambassadors” wasn’t an anamorph. It was just warped by the gravity produced by the apparently massive egos of the titular subjects.

LOL. Interesting, neat, painting. Cheers.

@4. Scott P. :

I seem to see a second distorted galaxy — just left of center, about a third of the way up. Anyone else see it?

Not sure. I see a few blue streaks+ which may or may not be part of the same untangled lensed galaxy we’re already discussing and what looks like a distorted and very blue barred spiral directly in line above the brightest elliptical of the cluster. Is that the one you were meaning?

*****

+ Blue streaks NOT meaning the eponymous historic world land speed record setting rocket car!

By: Frank Snively

Frank Snively — Thu, 09 Feb 2012 02:34:57 +0000

Answer to Thaneb’s question:

With very few exceptions, there will be no dispersion. The light follows a (null) geodesic through space-time, and since that is an inherent property of space, any light must follow the same path. Of course, intervening matter along the path (not the matter that is bending the light – that is somewhere else, in the cluster of galaxies) would affect the propagation a little bit; it is safe to assume there isn’t much matter along the geodesics.