Flying into deep space will certainly bring many mysteries, which we will not be able to solve in a very long time. And this is not surprising. As soon as the first messengers of the Earth passed the orbits of the giant planets, space immediately gave us a problem. And to solve it, it was even proposed to correct the laws of physics.
Pioneers
America's space exploration programs have always had resounding names and ambitious goals. Under the Mercury program, the Americans made their first manned flights and created the first astronaut corps. In the course of the next Gemini program, methods of rendezvous and docking in orbit were worked out. The third program of manned space flights was the notorious Apollo program. Its goal was manned flights to the moon. But for the study of interplanetary space and celestial bodies, the Pioneer program was launched.
As part of its missions, the United States sent several research probes into space between 1958 and 1978. Spacecraft flew to the Sun, Venus and the Moon, investigated comets approaching us. "Pioneer-3" discovered the second radiation belt of the Earth, and "Pioneer-7" participated in the study of Halley's comet. Today, two spacecraft of the program are well known. These are the Pioneer-10 probes (launched in March 1972) and Pioneer-11 (April 1973), one of the last ones launched.
Probe "Pioneer-10" in the process of assembly
wikipedia.org
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Later NASA launched other research programs. With new, more advanced probes. In 1977, already within the framework of the Voyager program, Voyager 1 and Voyager 2 were sent to the distant planets of the solar system. And in 2003, the New Frontiers program was launched, within which New Horizons, Juno and OSIRIS-REx went into space. But in the 50s, when the program was just beginning, its devices in the United States were considered pioneers of space, and therefore they were called "Pioneers". Pioneer 10 and Pioneer 11 were the first spacecraft to fly through the Main Asteroid Belt and the first to study Jupiter at close range.
The Pioneers could have been the first to go beyond the solar system, but in 1998 the faster Voyager 1 overtook the Pioneer 10, which had the yellow jersey of the leader on this solar system tour.
Anomaly
For the first time an anomaly in the flight path of the probes was discovered in the 1980s. By this time, the probes have already completed their main mission. Pioneer 10 flew close to Jupiter in December 1973, specifying its mass and measuring its magnetic field. Pioneer 11 approached the planet exactly one year later: in December 1974. After taking detailed pictures, he went to Saturn. In 1979, the device transmitted images of the planet and its satellite Titan to Earth.
The main mission ended, but it was decided to use the data from monitoring the flight path of the Pioneer-10 spacecraft to search for, as it was still assumed, the tenth planet of the solar system. And now it's the ninth (after the demotion in Pluto). If there was a deviation in the trajectory, then, as scientists believed, this would be a consequence of the gravity of an undiscovered planet. The deviation was found, but the cause of this anomaly was by no means a planet at the edge of the solar system. But, what is most interesting, the anomaly was subsequently found in the twin probe.
Illustration of the exit of "Pioneers" and "Voyagers" outside the solar system
wikipedia.org
Today, vehicles fly in different directions. Pioneer 10 is moving towards the edge of the Milky Way, in the direction of the constellation Taurus. Its twin, on the other hand, is towards the center of the Galaxy, towards the constellation of the Shield. It should be understood that both probes are now in free flight. Only the previously obtained acceleration and external forces affect the flight of spacecraft. Forces are gravitational and non-gravitational.
Among the non-gravitational ones, for example, the pressure of solar radiation, causing acceleration directed from the Sun. And the gravity of the Sun, on the contrary, pulls the vehicles towards the star, causing an acceleration directed towards the Sun, that is, it slows them down. All forces that can affect the flight of spacecraft are calculated and taken into account. Except for one. One unknown and incomprehensible force pulls the probes back. It is she who is the reason for the riddle of the "Pioneers". The power is negligible, but it is there. The latest calculations obtained by 2002 indicate that the magnitude of the unexplained negative acceleration is (8.74 ± 1.33) 10–10 m / s2.
This is negligible, but has already led to a deviation of the vehicles by about 400 thousand kilometers from the calculated trajectory. It would seem that the probes have flown billions of kilometers. At the time of the loss of communication with "Pioneer-10" (January 23, 2003), it was more than 12 billion kilometers away from us. These are 82 astronomical units, that is, 82 distances from the Earth to the Sun. Communication with "Pioneer-11" was lost on September 30, 1995, the device was already at a distance of 6.5 billion kilometers from the Sun, or 43 AU. e.
And what are these hundreds of thousands compared to billions of kilometers? But for science, these insignificant values can be of great importance. Deviation from the norm, from the usual understanding of things, that is, anomalies may indicate the presence of something significant, but still undiscovered. Moreover, in astrophysics.
An anomaly in the movement of Uranus led to the discovery of a new planet - Neptune. The anomaly in the motion of Mercury, discovered in 1859, was only explained by Albert Einstein's general theory of relativity, which he developed in 1915. The solution to the "Pioneers" anomaly may turn modern physics upside down or, conversely, be quite trivial. This is why it haunts many scientists.
The question may arise: how did scientists calculate the speed and, accordingly, the acceleration of the vehicles? Probes have long been unavailable for observation. Neither Hubble nor any other telescope will be able to see the probes flying away from us. The speed control of the probes is carried out by measuring the Doppler frequency shift of the radio signal, which is sent in the direction of the probe and received back from it. It is based on the same Doppler effect used to determine the speed of vehicles. The effect manifested itself in the form of the so-called violet shift, the shift of the radio signal to the short-wave region of the spectrum, which means that the probes began to slow down.
But if we are talking about an effect that can affect the movement of two probes, then it can also affect others? We have already said that there were others after the Pioneer program. But the Pioneers are in flight without additional course corrections for a long time. But the flight path and orientation of other probes are still corrected by the thrusters. Therefore, accurate measurements of the effect, if any, cannot be made.
Possible causes of the anomaly
Over the years that have been devoted to finding solutions to this puzzle, many assumptions have been put forward. And the first is errors in observations and interpretation of the data obtained. But he was abandoned almost immediately. The anomaly was attributed to various reasons. Braking on the interplanetary medium (dust, gas clouds, etc.). The gravitational attraction of Kuiper belt objects. Leaking gas, such as helium, used as a working fluid in radioisotope generators. The reason was also sought in the electromagnetic forces caused by the accumulated electric charge of the probes. And, of course, it was attributed to the influence of dark matter or dark energy. Not without suggestions to correct the existing physics. Previous assumptions provided a non-gravitational explanation for the effect. In 1983, the Israeli physicist Mordechai Milgrom proposed the so-called theory of modified Newtonian dynamics (MOND). She is an example of an alternative theory of gravity. According to MOND, when we are dealing with bodies moving with extremely low acceleration, Newtonian mechanics needs to be corrected.
However, the reason for the anomalous acceleration of the "Pioneers" seems to have been found. But first, let's say a little about the design of the devices. The probes are equipped with scientific instruments and a parabolic antenna with a diameter of 2.75 meters for communication with the Earth. All this equipment needed power supply. Look at the construction of the Pioneers. Do you see solar panels familiar to satellites in it? Not. For spacecraft exploring the distant planets of the solar system, there is no point in solar panels. As you move deeper into space, the intensity of solar radiation decreases. The energy of the sun is no longer sufficient for the operation of solar cells.
Diagram of the "Pioneer-10" apparatus
wikipedia.org
Unlike probes flying to the inner planets of our system, radioisotope thermoelectric generators using plutonium-238 are installed on board for flights to Jupiter, Saturn and other distant planets. These are not nuclear reactors. They work in a different way. Radioisotope generators use thermal energy, which is released during the natural decay of radioactive isotopes and, using a thermoelectric generator, convert it into electricity. Plutonium-238 is just such a radioactive isotope, the decay of which powers the equipment on board the probes. Each probe has four generators, which are fixed on two three-meter outrigger rods, away from the scientific instruments of the apparatus.
A research team was formed at the Jet Propulsion Laboratory of the US National Aerospace Agency to study the Pioneers anomaly. It was headed by our compatriot, a graduate of the Physics Department of Moscow State University Vyacheslav Turyshev. The researchers were able to build a mathematical model that explains the anomalous acceleration of the "Pioneers" at least 70%. In their opinion, the whole point is in the heat fluxes coming from the probe in different directions. And the main source of heat is radioisotope generators, which supplied energy to the onboard equipment. Heat was generated from the operation of the instruments. As the instruments were turned off, more and more energy was spent on heating the probes. Heat was radiated into space. It was the force of the recoil of thermal radiation that was underestimated when calculating the estimated flight path. However, the heat radiation pressure is uneven. In flight, the probes are stabilized by rotating around the longitudinal axis. The heat radiated perpendicular to the longitudinal axis is dissipated in all directions uniformly and does not affect the movement of the probes. But there is also radiation along the axis. And it radiates unevenly. Calculations have shown that the heat flux radiated in the direction of movement of the vehicles gives a greater return than that going in the opposite direction, that is, overpowers it and causes the effect of braking.that is, it overpowers it and causes an inhibition effect.that is, it overpowers it and causes an inhibition effect.
Rear view of the transmitting antenna
nasa.org
But what is the reason for the remaining 30%? Perhaps physicists from the Portuguese Institute of Plasma and Nuclear Fusion managed to find an explanation. They followed the same path as Turyshev's group. But we paid more attention to the transmitting antenna of the probes, which, we recall, has an almost three-meter diameter. Having made new calculations based on their mathematical model of the probes, they came to the conclusion that the thermal radiation reflected from the back side of the antenna gives the same missing impulse.
Well, the mystery that haunted the scientists seems to be solved. Humanity continues to explore space. For new puzzles and an exciting search for their solutions.
naturalphilosophy.org
Sergey Sobol