VCA 7.B. Anomalous Red Shifts: The Observations of Halton Arp

One astronomer who doubts the interpretation of all red shifts as Doppler effects is Halton Arp, who has served on the staff of the Hale Observatory at Mt. Palomar and is currently doing research at the Max Planck Institute near Munich, West Germany. At Palomar, Arp observed many examples of discordant red shifts that do not follow Hubble's law. His analysis suggests to him that red shifts in general may be due to something other than a Doppler effect.

Here we should ask why scientists generally interpret red shifts as being caused exclusively by the Doppler effect. It may be true that a Doppler effect produces a red shift, but how do we know that a red shift must be due to a Doppler effect? One of the main reasons for this conclusion is that, according to modern physics, the only phenomenon other than a Doppler effect that will produce a pronounced red shift is a powerful gravitational field. If light is going up against a gravitational field, it loses energy and undergoes a red shift. However, astronomers don't find this explanation applicable for stars and galaxies, because the fields would have to be of incredible strength to produce the observed red shift.

Arp argues that he has found objects with high red shifts in close proximity to ones with low red shifts (AR1-4, RC). According to the standard expanding-universe theory, an object with a small red shift should be relatively close to us, and an object with a large red shift should be far away. Thus, two objects that are relatively close to each other should have similar red shifts.

But Arp gives the following example: The spiral galaxy NGC 7603 is connected to a companion galaxy by a luminous bridge, yet the companion galaxy has a red shift 8,000 kilometers per second higher than that of the spiral galaxy. Judging by the disparity in their red shifts, the galaxies should be at vastly different distances-to be precise, the companion should be about 478 million light-years further away-yet strangely, the two galaxies seem close enough to be physically connected. For comparison's sake, our own galaxy, the Milky Way, is said to be just 2 million light years from its nearest neighbor, the galaxy Andromeda.

Of course, there are some defenders of the standard view who strongly disagree with Arp's interpretation. John N. Bahcall, of Princeton's Institute of Advanced Studies, maintains there is no reason to suppose that the two galaxies are connected (RC). The objects are actually distant from each other and just appear to be closely associated. The so-called luminous bridge is there, but the more distant galaxy just happens to be lined up behind it from our point of view.

To illustrate his criticism, Bahcall gives this specific rebuttal: He shows a photograph of a star within our own Milky Way galaxy apparently connected to a distant galaxy by what appears to be a luminous bridge. Are they connected? Bahcall points out that this is clearly impossible because the star is a bright foreground star in our own galaxy, while the distant galaxy is 44 million light-years away.

However, Arp responds by saying that Bahcall is just being frivolous. The galaxy he shows is not in any way unusual. The luminous bridge to the star is simply one of its normal spiral arms. But in the example Arp himself has chosen, the bridge is an unusual structure, not normally found in such galaxies. The likelihood that two galaxies of this type could be found in such a relationship is far less than the likelihood that a star in the Milky Way will be lined up with an ordinary galaxy.

Arp has found many other examples that seem to violate the traditional understanding of the red shift. Here is one of the most controversial of these discoveries: Near the spiral galaxy NGC 4319 is a quasar, Makarian 205, apparently connected to the galaxy by a luminous bridge. The galaxy has a red shift of 1,800 km per sec, giving it a distance of about 107 million light-years. The quasar has a red shift of 21,000 km per sec, which should mean that it is located 1.24 billion light-years distant. But Arp suggests that they are definitely connected and that this shows that the standard interpretation of the red shift is wrong in this case. (We may note, by the way, that the very fact that astronomers express red shifts in terms of kilometers per second shows their commitment to the idea that the red shifts are Doppler effects.)

Critics took their own photographs of NGC 4319 and claimed not to have found the connecting bridge shown in Arp's picture. Others said the bridge was a "spurious photographic effect." But recently, Jack M. Sulentic, of the University of Alabama, did extensive photometric studies of the two objects and concluded that the connecting bridge is real (SU).

Another example of discordant red shifts noted by Arp is found in the highly unusual chain of galaxies called Vorontsov-Velyaminov 172, after its Russian discoverers. In this chain, the smaller, more compact member has a red shift twice as great as the others.

In addition to pairs of galaxies with discordant red shifts, Arp points out something even stranger-it appears that quasars and galaxies can eject other quasars and galaxies. Here are some examples: The exploding galaxy NGC 520 has a fairly low red shift. Located along a straight line running to the southwest from the galaxy are 4 quasars of the faint type. Arp says that these faint quasars are the only ones in this region. Could it simply be an accident that they are arranged almost exactly on a straight line from the galaxy? Arp says the chances of this are extremely remote and suggests that the quasars were ejected from the exploding galaxy.

Interestingly enough, the quasars have much larger red shifts than the galaxy that seems to be their parent. This is remarkable, since according to the standard theory of the red shift, the quasars should be much further away than the galaxy. Arp interprets this and other, similar examples by proposing that freshly ejected quasars are born with high red shifts, which gradually decrease as time passes.

Some scientists question whether it is really possible for galaxies to eject other massive objects such as galaxies or quasars. In response, Arp points to a striking photograph of the giant galaxy M87 ejecting a jet of material. When we look at the galaxies of the elliptical type in the region around galaxy M87 (which is also elliptical), we find that they all fall on a line drawn in the direction of the jet of ejected material. This suggests to Arp that these galaxies have been ejected by M87.

How is it that a galaxy can emit another galaxy? If a galaxy is an "island universe" consisting of a vast aggregate of stars and gas, how can it emit another galaxy, which is a similar aggregate of stars and gas?

It has been argued that radioastronomy may provide a clue. In recent times, radioastronomers have agreed that vast radio-emission areas can be ejected from galaxies. These emission areas exist in pairs on either side of some galaxies. To explain this, astronomers have postulated gigantic spinning black holes in the centers of the galaxies that gobble up nearby stars and spit out material in both directions along their axis of spin. However, if Arp's analysis is correct, one has not only to explain the radiating emission regions, which may be composed of a thin gas, but also how entire galaxies or precursors of galaxies might come flying out.

Regarding the red shifts of such ejected galaxies and quasars, Arp has found the following: The ejected objects, although in close proximity to the parent objects, have much higher red shifts. Arp maintains this can only mean that their red shifts are not due to the Doppler effect. That is, they do not measure the speed at which the object is receding. Rather, the red shift has something to do with the actual physical state of the object.

But the present laws of physics provide no inkling of what this state might be. Since a galaxy is thought to be composed of many individual stars plus clouds of dust and gas, what qualities could it have that would result in a red shift not due to velocity or gravitation? This cannot be explained in terms of known physical principles.

This seems to call for new physics. But that opens up a whole Pandora's box, because modern cosmology is completely committed to the assumption that everything we see in the universe can be explained by the known laws of physics. If the physical laws are fundamentally changed, then all the models based on them are brought into question.

Of course, Arp's findings are very controversial, and many astronomers doubt that the associations between galaxies and quasars he speaks of could actually be real. But this is only one line of evidence suggesting that the standard interpretation of galactic red shifts might be in need of revision.