In the framework of SETI (Search for Extraterrestrial Intelligence) one of the important projects was the search for the interstellar radio communication. A rather different and quite original method was proposed by the prominent physicist Freeman Dyson in 1960, who suggested that if an extraterrestrial intelligence has reached a level of supercivilization, it might consume an energy of its own star. For this purpose, to have the maximum efficiency of energy transformation, it would be better to construct a thin shell completely surrounding the star. In the framework of this approach the author assumes that the mentioned superintelligence observed by us will have been in existence for millions of years, having reached a technological level exceeding ours by many orders of magnitude. Kardashev in his famous article, examining the problem of transmission of information by extraterrestrial civilizations, has classified them by a technological level they have already achieved: (I) – a technological level close to the level of the civilization on earth, consuming the energy of the order of 4 × 1019 ergs s¯1; (II) – a civilization consuming the energy of its own star – 4×1033 ergs s¯1 and (III) – a civilization capable of harnessing the energy accumulated in its own galaxy: 4×1044 ergs s¯1. In this classification Dyson’s idea deals with the civilization of type-II, consuming the energy exceeding ours approximately 4×1033 / 4×1019 = 1014 times. If we assume that an average growth rate of 1% per year in industry is maintained, the level of typeII civilization might be achieved in ∼ 3000 years, being quite reasonable in the context of the assumption that a civilization exists millions of years.
Dyson has suggested that if such a civilization exists, then it is possible to detect it by observing the spherical shell surrounding the star. In particular, it is clear that energy radiated by the star must be absorbed by the inner surface of the sphere and might be consumed by the civilization. The author implied that the size of the sphere should be comparable with that of the Earth’s orbit. It is clear that to have energy balance, the spherical shell must irradiate the energy, but in a different spectral interval: in the infrared domain, with the black body temperature of the order of (200 − 300) K.
Now, Osmanov presented a rather different idea how to search an advanced intelligence. In the framework of Dyson’s idea, the spherical shroud (with radius of the order of (1 − 3)AU) is constructed around stars. It is clear that in order to consume almost the total energy radiated by the star, it must be imbedded inside a closed spherical shell, requiring enormous material to construct it. On the other hand, it is very well known that pulsars – rapidly rotating neutron stars – emit huge energy in narrow channels (see Figure 1), therefore, if a supercivilization exists it can in principle utilize the energy of these objects. But in these cases, instead of sphere-like envelopes the super intelligence has to use ring-like structures around the pulsars. But why? Well, its because slow down luminosity for the relatively slowly rotating pulsars is of the order of
From this, it is clear that the energy budget is very high, forcing a supercivilization construct a “ring” close to the host object.
But where exactly this ring located? Well, osmanov have also answered this question in his paper. According to him, if the angle between the rotation axis and the direction of emission, α, is close to 90°, the ring will be located in the equatorial plane of the neutron star.
Moreover, he examined the size of ring required for slowly rotating pulsars and millisecond or rapidly rotating pulsars.
We have found that a size of the “ring” should be of the order of (10¯4−10¯1)AU with temperature interval (300−600)K for relatively slowly rotating pulsars and (10−350)AU with temperature interval (300−700)K for rapidly spinning neutron stars, respectively.Told Osmanov, author of the study
For slowly rotating pulsars, by considering the parameters P = (0.5 − 2) s; P˙ = 10¯15 ss¯1; P˙ = 10¯14 ss¯1; P˙ = 2 × 10¯14 ss¯1, he showed that the size of the ”ring” must be by (1 − 4) orders of magnitude less than those of the Dyson sphere, which is thought to be of the order of 1 AU. The corresponding temperatures of the artificial construction should be in the following interval (300 − 600)K.
Later, by considering the parameters of millisecond pulsars, P = (0.01 − 0.05)s; P˙ = 10¯13 ss¯1; P˙ = 2 × 10¯13 ss¯1; P˙ = 4 × 10¯13 ss¯1, he found that the radius of the ”ring” should be of the order of (10 − 350)AU with an enormous mass 1032 g exceeding the total planetary mass (except the central star) by several orders of magnitude. Therefore, it is clear that millisecond pulsars become less interesting in the context of the search for extraterrestrial superintelligence. Contrary to this class of objects, for slowly rotating pulsars the corresponding masses of the Dyson structures should be three orders of magnitude less than the Earth mass.
Then, he have examined the tidal stresses in terms of radiation and pulsar winds and it has been shown that they will not significantly perturb the Dyson construction located in the habitable zone if the area density of the ring satisfies a quite realistic condition λ ≫ 3.4×10¯6 g cm¯2.
“If we want to maintain the stability of the structure, the radiation force should be small compared to gravitational force. When we imposed this condition, we will get the above value 3.4 ×10…….. This aforementioned estimate showed that, for realistic scenarios, the emission cannot perturb the Dyson construction.”
“…moreover, one should apply the pulsar wind kinematic luminosity, that cannot exceed the slow-down luminosity, instead of the radiation term the same condition. After considering the max possible kinematic wind luminosity, the critical surface density will be of same order of magnitude. Therefore, the Dyson structure can survive such an extreme pulsar environment…”— wrote Osmanov, author of the study
In addition, he have examined the stability problem of the ring’s inplane dynamics and it has been shown that under certain conditions the power required to restore the equilibrium position might be much less than the power extracted from the pulsar. Also considering the problem of radiation protection they have found that it is quite realistic to reduce the high level of emission by many orders of magnitude.
“It is worth noting that in the framework of the paper we do not suggest that an advanced civilization would arise around a massive star, surviving its supernova. On the contrary, we consider the possibility to colonize the nearby regions of pulsars building large-scale Dyson structures.”— told Osmanov, author of the study
“Generally speaking, the total luminosity budget of a pulsar is emitted over a broad range of wavelengths, that can be harvested by means of the Faraday’s law of induction, transmitting electromagnetic energy into that of electricity. As we see, the pulsars seem to be attractive sites for super advanced cosmic intelligence and therefore, the corresponding search of relatively small (0.0001AU-0.1AU) infrared ”rings” (with the temperature interval (300 − 600)K) might be quite promising.”, concluded Osmanov.
Reference: Osmanov, Z. (2016). On the search for artificial Dyson-like structures around pulsars. International Journal of Astrobiology, 15(2), 127-132. doi:10.1017/S1473550415000257
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