We know that the magnetic field surrounds the earth, the sun and all the galaxies. Twenty years ago, astronomers began to detect the magnetic field of the whole galaxy cluster, including the space between one galaxy and another. Invisible magnetic lines of force jump in space between galaxies, just like the grooves of our fingerprints.
Last year, astronomers finally managed to examine a sparse space area, that is, a vast area between galaxy clusters. There, they found the largest magnetic field to date:/kloc-the magnetized space of 0/0 billion light years, which spans the entire length of the "filament" of the cosmic web. A second magnetized filamentary object was found in other parts of the universe with the same technology. "We may have just seen the tip of the iceberg," said Federica Govoni of the National Institute of Astrophysics in Cagliari.
The question is: Where do these huge magnetic fields come from?
Franco Vazza, an astrophysicist at the University of Bologna, said: "Obviously, it has nothing to do with the activity of a single galaxy, the activity of a single explosion or the wind generated by a supernova." Franco Vazza, an astrophysicist at the University of Bologna, said, "This is far beyond it." Franco Waza made the most advanced computer simulation of the cosmic magnetic field.
One possibility is that the magnetism of the universe is primitive and can be traced back to the birth of the universe. In that case, weak magnetism should be everywhere, even in the "gap" of the cosmic web-the darkest and most empty area in the universe. The ubiquitous magnetic field will sow the seeds for stronger magnetic fields in galaxies and clusters of galaxies.
Primitive magnetism may also help solve another cosmological problem called Hubble tension, which may be the hottest topic in cosmology.
The core problem of Hubble tension is that according to its known composition, the expansion of the universe seems to be much faster than expected. In a paper published online in April, cosmologists Karsten Jedamzik and Levon Pogosian believe that the weak magnetic field of the early universe will lead to the faster expansion of the present universe.
Kamionkowski and others say that more inspections are needed to ensure that the early magnetic force will not affect other cosmological calculations. Even if this idea works on paper, researchers need to find conclusive evidence of the original magnetic force to ensure that it is an indispensable substance to shape the universe.
Meanwhile, astrophysicists have been collecting data. A lot of evidence makes most people doubt whether the magnetic field really exists.
1600, British scientist william Gilbert studied magnets-natural magnetized rocks that people have magnetized into compasses-which made him think that their magnetism "imitated a soul". He correctly speculated that the earth itself is a "huge magnet" and the diamond-shaped rock "faces the poles of the earth".
Every time a charge flows, a magnetic field is generated. For example, the earth's magnetic field comes from its internal "generator", that is, the current stirred by molten iron in the core. The magnetic fields of refrigerator magnets and iron ore come from electrons rotating around their constituent atoms.
However, once the moving charged particles generate a "seed" magnetic field, they can become bigger and stronger by aligning the weaker magnetic field with it. Tollsten Anslin, a theoretical astrophysicist at Max Planck Institute for Astrophysics, said: "Magnetism is" a bit like a creature "because magnetic fields are absorbed into every free energy that they can maintain and grow. Their existence will expand and affect other regions and develop in these regions. "
Ruth Durrer, a theoretical cosmologist at the University of Geneva, explained that besides gravity, magnetism is the only force that can shape the large-scale structure of the universe, because only magnetism and gravity can "touch you" from a distance. In contrast, electricity is local and transient, because the positive and negative charges in any area will be neutralized as a whole. But you can't cancel the magnetic field; They tend to live cumulatively.
In last year's paper, astronomer Reinout van Weeren of Leiden University and 28 co-authors concluded that there is a magnetic field in the filament between the galaxy cluster Yinling 399 and Yinling 40 1, through which high-speed electrons and other charged particles are redirected. When their paths are twisted in a magnetic field, these charged particles will emit weak "synchrotron radiation".
Synchrotron signals are strongest at low radio frequencies, so they can be detected by 20,000 low-frequency radio antenna arrays LOFAR distributed in Europe.
The team actually spent eight hours exploring on 20 14, collecting data from filamentary objects between galaxies. However, since the radio astronomy community has spent several years studying how to improve the calibration of LOFAR measurement, the data has been waiting. The earth's atmosphere refracts radio waves that pass through it, so LOFAR looks at the universe as if it were from the bottom of a swimming pool.
Researchers solve this problem by tracking the swing of "beacons" (radio transmitters with accurate positions) in the sky and correcting them to eliminate the ambiguity of all data. When they applied the deblurring algorithm to the data of filamentary objects, they immediately saw the brilliance of synchrotron emission.
Filamentous objects seem to be magnetized all over their bodies, not just near clusters of galaxies moving from both ends to each other. The researchers hope that the 50-hour data set they are analyzing now can reveal more details. Other recent observations have also found a magnetic field passing through the second filament. The researchers plan to publish the results of this study as soon as possible.
There is a huge magnetic field in at least these two filaments, which provides important new information. "It stimulates quite a lot of activities, because now we know that the magnetic field is relatively strong," van Waylon said.
If these magnetic fields appear in baby universes, the question becomes: How? "People have been thinking about this for a long time," said Tammy Vacha Spathy of Arizona State University.
Vachapati proposed in 199 1 that during the weak electromagnetic phase transition (that is, the moment after the big bang), when the electromagnetic force and weak nuclear force become obvious, a magnetic field may be generated. Others think that after the proton is formed, it will produce magnetism within a few seconds. Or soon: the late astrophysicist Ted Harrison pointed out in the original magnetization theory of 1973 that the turbulent plasma of protons and electrons may make the first magnetic field rotate.
Others believe that during the expansion of the universe, space was magnetized before that. It is said that the explosive expansion of space is the beginning of BIGBANG itself. This will not happen until a billion years later when the structure grows.
The way to test the magnetization theory is to study the magnetic field pattern of the most primitive patches in the galactic space, such as the quiet parts of filamentous objects and more empty holes. Some details (such as whether the magnetic lines of force are smooth, spiral or "curved in any direction, such as something like a wool ball", and how the pattern changes at different positions and proportions) carry rich information, which can be compared by theory and simulation. For example, if a magnetic field is generated during a weak phase transition, as Vachapati suggested, the magnetic field lines generated should be spiral, "like a bottle opener," he said.
The difficulty is that the force field in the void is difficult to detect.
Michael faraday, a British scientist, first proposed a method in 1845 to detect the magnetic field by rotating the polarization direction of light. The amount of Faraday rotation depends on the strength of the magnetic field and the frequency of light. Therefore, by measuring the polarization at different frequencies, we can infer the magnetic field intensity along the line of sight. Anslin said: "If you operate in different places, you can make 3D maps."
Researchers have begun to use LOFAR to roughly measure Faraday rotation, but it is difficult for telescopes to pick up weak signals. A few years ago, astronomer Govoni of the National Institute of Astrophysics and his colleague Valentina Vacca designed an algorithm to statistically analyze Faraday's tiny rotation signal by superimposing the measurement results of many hollow areas. Waka said: "In principle, this can be used in the void of the universe."
However, when the giant international project of the next generation radio telescope (one square kilometer array) is launched in 2027, Faraday technology will really take off. "SKA should produce a wonderful Faraday grid," Enslin said.
So far, the only magnetic evidence in the void is what the observer can't see when observing the so-called bright variant behind the void.
Glossy variants are gamma rays and other high-energy beams and bright matter beams driven by supermassive black holes. When gamma rays travel in space, they sometimes collide with ancient microwaves, which are converted into electrons and positrons. These particles then decay into low-energy gamma rays.
However, Andrii Neronov and Vovk of the 20 10 Geneva Observatory think that if the radiation passes through the magnetized hole, it seems that there will be a lack of low-energy gamma rays. The magnetic field deflects electrons and positrons to the line of sight. When they decay into low-energy gamma rays, these gamma rays will not point at us.
Indeed, when Nironov and Vovk analyzed the data of Yao's variant from a proper position, they saw its high-energy gamma rays, but they could not see the low-energy gamma ray signals. Vachapati said: "No signal is a signal."
No signal is not conclusive evidence, and someone has put forward another explanation for the disappearance of gamma rays. However, subsequent observations have increasingly pointed out Nironov and Vovk's hypothesis that holes are magnetized. "This is the view of most people," Dulle said. Most convincingly, at 20 15, a team superimposed many measurements of bright variants behind the hole and managed to find out the faint low-energy gamma-ray halo around the hole. If you use a weak magnetic field to disperse particles, the effect is as expected-the magnetic field strength is only one tenth of that of a refrigerator magnet.
Surprisingly, the exact amount of the original magnetic field may be just what is needed to solve the Hubble tension (the strange and rapid expansion of the universe).
This is what Bogosian realized when he saw the recent computer simulation of Carlsten Jadanzke of Montpellier University and his collaborators. The researchers added a weak magnetic field to the simulated young universe filled with plasma, and found that protons and electrons in the plasma flew along the magnetic field lines and gathered in the region with the weakest magnetic field strength. This cluster effect makes protons and electrons combine into hydrogen earlier than before (an early phase change called recombination).
Bogosian found that this can solve the problem of Hubble tension when reading Jadanzke's paper. Cosmologists calculate the speed at which space should expand today by observing the ancient light emitted in the process of reorganization. The light shows a young universe, full of spots. These spots are formed by vibrating sound waves in the original plasma.
If recombination occurs earlier than expected due to the concentration effect of the magnetic field, the sound wave may not travel so far and the light spot will be smaller. This means that the spots we see in the sky after reorganization must be closer to us than the researchers thought. The light from the spot must travel a short distance to reach us, which means that the light must always travel through a space that expands faster. "It's like trying to run on an expanding surface; You walk shorter distances, "Pogosian said.
Therefore, a smaller cluster of galaxies means a higher inferred expansion rate of the universe-making the inference rate closer to the measured actual flight speed of supernovae and other celestial bodies.
"I think, wow," Bogosian said, "this may point out the actual existence of [magnetic field] for us. So I immediately wrote to Carsten. Just before the COVID-19 blockade, the two met in Montpellier in February. Their calculations show that the original magnetic force needed to solve the Hubble tension problem is also consistent with the observation results of Yao variant, and the estimated size of the original magnetic field is consistent with the size of the magnetic field needed to grow a huge magnetic field across galaxy clusters and filamentous objects. " "All these are very consistent," Pogosian said. However, it needs more facts to prove its correctness. "