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Cosmic Headlights and the Origin of Gamma Ray Bursts

by Eric J. Heller
Departments of Chemistry and Physics
Harvard University, Cambridge, Massachusetts

 

Figure 1: The positions in galactic coordinates of the GRBs in the BATSE 4B catalog, showing the isotropy of the burst sky distribution (see C.A. Meegan, et al., Nature, vol. 355, 1993, p. 143.


Gamma-ray bursts pose one of the greatest mysteries of modern astrophysics. Almost every day, there is a huge, localized burst of gamma-rays lighting up the sky, which often outshines all the other gamma ray sources in the sky put together. Then the source of the burst vanishes, often in a few seconds. The bursts come from all over the sky, seemingly at random. Until now there has been no convincing explanation for them. The answer, it turns out, may be automotive in nature

The Mystery of Gamma Ray Bursts

Gamma ray bursts (GRB) were discovered in 1967 by satellite-borne detectors looking for violations of the Nuclear Test Ban Treaty. They are extremely bright sources of radiation, typically lasting for seconds. Some are very sharply peaked in time, others have a longer falloff. Burst time-scales go through the 30 ms scale to hundreds of seconds. Even if the GRBs we see are somehow collimated toward us (as we shall argue they are) , they are by far the brightest electromagnetic events in the Universe. They are more or less randomly distributed across the sky, as seen in Figure 1, and happen about once a day. There is strong evidence that the GRBs seen so far are extragalactic, since recent observations have associated faint galaxies to the burst sights. It is now known that they emanate from distant galaxies. While the bursts were detected in the gamma region of the spectrum, there are also x-ray and visible portions of the spectrum. GRBs remain an active area of research [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]. Typical bursts are shown in Figure 2 . A galaxy from which another burst originated is shown in Figure 3.

Figure 2: Sample of GRBs detected by the BeppoSAX/GRBM. It shows just an example of the possible morphology, duration and intensity variety of the GRBs


The explanations for these bursts have been diverse. Most involve black holes created by massive stars. Since the collimation issue is not resolved, the total energy in the bursts ranges enormously, depending on the solid angle assumed for the beam. If the radiation were isotropic, the total energy involved would be almost unimaginable and very hard to accommodate into existing theory. On the other hand if the bursts are extremely collimated, and we just happen to see the ones aimed at us, the energies are more modest. None of the proposed models is very satisfactory, in that aspects of the data remain unexplained or that unknown physics has to be arbitrarily invoked. Here, we give a simple explanation showing they are in fact the result of routine activities by extraterrestrials.

Explanation

The explanation of GRBs falls into place if we consider the activities of extraterrestrial intelligent beings. It is assumed that such beings, in our galaxy or other galaxies, are quite capable of space travel over great distances, at speeds near the speed of light, c. The relativistic time dilation , where , dictates that travelers have a huge advantage in traveling close to the speed of light, in terms of the space ship clock time to arrive at a destination. The energy requirements, E, on the other hand get arbitrarily large as the speed of light is approached, i.e. . We are only 250 years since the invention of the steam engine; advanced societies could easily have had a million-fold more time to develop technology. We dare not assume they are limited in their capacity to generate enormous amounts of energy.

Space travel at relativistic speeds is not without its hazards. It is well known that “brown” matter and other debris populates intragalactic space, and perhaps intergalactic space, with some density. Objects ranging in size from baryons and atoms to masses of the order of Jupiter might be encountered, though the larger ones would certainly be known ahead of time, or easily seen. Smaller sized objects are another issue. We assume here that a collision at relativistic speeds with something the size of a baseball, or perhaps even small molecules, is bad even for space vehicles of very advanced societies. At the very least, such vehicles must “look ahead” for larger objects it would collide with, and move out of the way when they are detected. It should also have a way of moving the much more numerous small objects out of harm’s way.

Figure 3: Galactic region (left) and host galaxy (right) from which the gamma ray burst GRB 9901231 originated (from reference [21])

In other words, space ships must have headlights, and perhaps beams powerful enough to disintegrate or displace small bodies well in advance of arrival. These would naturally need to be extremely collimated. The requirement to see far enough ahead might make them quite energetic. An observer along the line of the path vehicle would always see very blue shifted (i.e., mostly gamma) radiation, since we would see only those beams from ships traveling directly toward us at relativistic speeds. But why do we see a “burst” of 0.1–10 seconds?

If a space vehicle in another galaxy were traveling exactly in our direction (of course at some time in the past) then perhaps we should see their “headlights” for more than a few seconds. However, several explanations exist for this, all of which can coexist. The burst may be an indication that the ship has its low beams on most of the time, switching to high beam only long enough to destroy objects in its path. This would explain their short and variable duration (the time required to destroy different debris is variable), and the asymmetry in time of some GRBs, some of which have a long time tail (destruction beams from ships may be chirped, for example, visible radiation followed by microwave, to increase effectiveness). Secondly, depending on the collimation, extremely slight deflections in path of the vehicle, or deflection of the headlight beam by changes in matter distribution in the vicinity of the vehicle would be sufficient to explain the brief duration of the typical gamma ray “flash”. It is also possible that small objects, once detected, are obliterated with a focused flash from the vehicle. Thus the variation in the duration of the flashes, their spectral content, and the total energy fluence are easily attributed to variations in source spectral content, propagation fluctuations of the type just mentioned, and earth’s position in the beam as it sweeps by.

Proposal for a Test

The solar system is sufficiently large to test the idea of extreme collimation of the beam. Let us suppose that the beam has an initial width of 100 m, with a mean wavelength of 10-12 m, in the gamma region. Using the asymptotic formula for the spreading of a Gaussian beam (Born and Wolf, Principles of Optics), we have the angular spread in radians, , given by
radians (1)



Figure 4. Headlights. This particular example is of terrestrial origin.

After one billion years of travel this beam would spread to a size of about 106 kilometers, only about 1% of the earth-sun distance. If the GRBs are remnants of destruction beams, their width at the beam waist might be 100 times smaller, giving a width a billion years later on the order 1 AU. These figures make it worthwhile to contemplate building a solar orbiting gamma ray camera, in order to detect differences between arrival signatures on earth and on the satellite which might reveal a beam width on the order of a few AUs or less.

Conclusion

We have shown that GRBs are explained as byproducts of narrowly collimated headlights and protection beams of extraterrestrial vehicles in other galaxies, where the bursts are known to originate. These beams would have an approximately 10–15 radian spread. This explanation requires ten to twenty orders of magnitude less energy in the source than an assumed astrophysical “collimated” source with a beam spread of 1 to 10 degrees.

No one has seen a GRB originating from within our own galaxy. No doubt there are extraterrestrials traveling around here too, but the beams would be very narrow due to a thousand-fold or greater reduction in propagation distance, and conceivably destructive. Probably we have never been “hit” by one of them. Indeed, tra_c laws or common courtesy may prohibit aiming of such concentrated radiation toward inhabited planets in one’s own galaxy; however, other galaxies are much too distant to have to worry about, explaining why we see bursts only from distant galaxies.

The GRBs originate only within distant galaxies as far as we know. This is easily explained, since extragalactic travel is either out of the question (even for advanced societies) because of the great distances involved, or else intergalactic space is so empty that it is common practice to leave your headlights off when traveling between galaxies.

Editor’s note: This work is consonant with the evidence amassed by Scott Sandford of NASA that internal combustion engines may be common in interstellar space. See “Proof that UFOs are Powered by Internal Combustion Engines,” Scott A. Sandford, AIR 6:2.

References

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