2020-07-05

Hidden magnetic universe begins to be discovered

By yqqlm yqqlm

Astronomers believe that the universe is full of magnetic fields, even in the void of the universe. When cosmologists came up with a new method to find the magnetic field of the deep space of the universe, they used this method and found the magnetic field there.

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We know that the magnetic field surrounds the earth, the sun and all galaxies. Twenty years ago, astronomers began to probe the magnetic field of entire galaxy clusters, including the space between one galaxy and another. Invisible magnetic field lines jump in the space between galaxies like the grooves of our fingerprints.

Last year, astronomers finally managed to examine a relatively sparse region of space, the vast area between galaxy clusters. There they discovered the largest magnetic field to date:a magnetized space of 10 million light years, spanning the entire Cosmic Web“filament” length. The second magnetized filamentary object has been discovered elsewhere in the universe by the same technique. Federica Govoni of the National Institute of Astrophysics in Cagliari, Italy, said:”We may just see the tip of the iceberg.”

The question is:where do these huge magnetic fields come from? Coming?

Astrophysicist Franco Vazza of 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.” Franco Vaza conducted the most advanced computer simulation of the cosmic magnetic field.

One possibility is that the magnetic force of the universe is primitive and has been traced back to the birth of the universe. In that case, the weak magnetic field should exist anywhere, even in the”gap” of the cosmic web-the darkest and emptyest region in the universe. The ubiquitous magnetic field will sow the stronger magnetic fields that grow in galaxies and clusters.

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The original magnetism may also help solve another alleged This is the cosmological problem of Hubble tension, which may be the hottest topic in cosmology.

The core problem of Hubble tension is that, based on its known composition, the universe seems to expand much faster than expected. In a paper published online in April and reviewed by the Physical Review Letter, cosmologists Karsten Jedamzik ​​and Levon Pogosian believed that in the early universe The weak magnetic field will cause the universe to expand faster today.

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The original magnetic alleviates the Hubble tension problem, so much so that Jie Danzik and Bogosian’s papers have aroused rapid attention. Mark Kaminkovsky, a theoretical cosmologist at Johns Hopkins University, said:”This is an excellent paper and idea.” He proposed other solutions to the Hubble tension.

Kamionkowski (Kamionkowski) and others said that more checks are needed to ensure that early magnetic forces 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 that shapes the universe.

Nevertheless, in the process of discussing the Hubble tension for many years, no one has considered magnetic force before, which may be strange. Pogosian, a professor at Simon Fraser University in Canada, said that most cosmologists hardly think of magnetism. He said:”Everyone knows that this is a big problem.” But for decades, there has been no way to prove whether the magnetic field is really omnipresent, nor can it prove that it is the original part of the universe, so cosmologists are very big To a lesser extent.

At the same time, astrophysicists have been collecting data. A lot of evidence makes most people doubt that the magnetic field actually exists.

Magnetic Soul of the Universe

In 1600, British scientist William Gilbert’s study of magnets-people It has magnetized it into a natural magnetized rock of compasses-making him think that their magnetic force”imitation of a soul”. He correctly speculated that the earth itself was a”giant magnet”, and the rhomboid rock”looked toward the poles of the earth.”

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Every time a charge flows, a magnetic field is generated. For example, the earth’s magnetic field originates from the”generator” inside it, that is, the current that molten iron stirs in its core. The magnetic fields of refrigerator magnets and iron ore come from electrons that rotate around their constituent atoms.

However, once the charged particles in motion generate a”seed” magnetic field, they can become larger and stronger by aligning the weaker magnetic field with it. Magnetism is “somewhat like living creatures,” said Tosten Ensling, a theoretical astrophysicist at the Max Planck Institute for Astrophysics in Germany, “because the magnetic field absorbs into every free energy source that they can maintain and grow . Their presence will expand and affect other regions and develop in these regions.”

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Ruth Durrer, a theoretical cosmologist at the University of Geneva, explained that in addition to gravity, magnetic force is the only force that can shape the large-scale structure of the universe, because only magnetic force and gravitation can be very long.”Extend to you” in distance. In contrast, electricity is local and transient, because the positive and negative charges in any region will be neutralized as a whole. But you cannot cancel the magnetic field; they tend to accumulate survival.

Astronomer Reinout van Weeren of Leiden University and 28 co-authors inferred in the paper last year that the wire between the galaxy clusters Abell 399 and Abell 401 A magnetic field exists in the object by redirecting high-speed electrons and other charged particles passing through it. When their path is twisted in a magnetic field, these charged particles release weak”synchrotron radiation.”

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The synchrotron signal is strongest at low radio frequencies, so , Can be detected by 20,000 distributed low-frequency radio antenna array LOFAR in Europe.

The team actually conducted an eight-hour probe in 2014, collecting data from filamentous objects between galaxies, but because the radio astronomy community spent years studying how to improve For the calibration of LOFAR measurement, the data has been in a waiting state. 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 solved this problem by tracking the swing of”beacons” (radio transmitters with precise known positions) in the sky and correcting them to eliminate all data ambiguities. When they applied the deblurring algorithm to the data of the filamentous celestial bodies, they immediately saw the light emitted by the synchrotron.

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Filamentous objects appear to be magnetized throughout, and Not just near the Milky Way star cluster moving towards each other from both ends. The researchers hope that the 50-hour data set they are analyzing now can reveal more details. Other recent observations have also discovered a magnetic field throughout 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. Van Wellen said:”It stimulates quite a lot of activities, because now we know that the magnetic field is relatively strong.”

Light passing through the void

If these magnetic fields appear in the baby universe, the question becomes:how?”People have been thinking about this for a long time,” said Tanmay Vachaspati of Arizona State University.

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In 1991, Vachapati proposed that During the phase transition (that is, immediately after the Big Bang), a magnetic field may be generated when the electromagnetic force and weak nuclear force become apparent. Others believe that after protons are formed, magnetism will occur after a few seconds. Or soon after:The late astrophysicist Ted Harrison (Ted Harrison) pointed out in the original theory of magnetization in 1973 that the turbulent plasma of protons and electrons may rotate the first magnetic field.

Some people have suggested that during the expansion of the universe, before all of this, space has been magnetized. It is said that the explosive expansion of space is the beginning of the Big Bang itself. This situation cannot happen until the structure grows a billion years later.

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The method to test magnetization theory is to study the most primitive in the space of the Milky Way The magnetic field patterns in the plaques, such as the quiet parts of filamentous celestial bodies and the empty void. Some details (such as whether the magnetic field lines are smooth, spiral or”curved in any direction, such as something like a ball of yarn”, and how the pattern changes in different positions and different proportions) carry a wealth of information, which is It can be compared with theory and simulation. For example, if, as suggested by Wachappati, if a magnetic field is generated during the electroweak phase transition, then the magnetic field lines should be helical,”just like a bottle opener,” he said.

The difficulty is that the force field in the void is difficult to detect.

A method first proposed by the British scientist Michael Faraday in 1845 to detect the magnetic field by rotating the polarization direction of light. The amount of &34; Faraday rotation &34; depends on the strength of the magnetic field and the frequency of light. Therefore, by measuring the polarization at different frequencies, you can infer the magnetic strength along the line of sight. Enslin said:”If you operate in different places, you can make 3D maps.”

Researchers have begun to use LOFAR to make rough measurements of Faraday rotation, but it is difficult for the telescope to pick up weak signals. The astronomer Govoni of the National Institute of Astrophysics and colleague Valentina Vacca designed an algorithm a few years ago. This algorithm superimposes the measurement results of many void areas from Faraday’s subtle rotation signals are analyzed statistically. Vaka said:”In principle, this can be used for the universe void.”

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However, when the giant international project of the next generation radio telescope (a square kilometer array) is launched in 2027, Faraday technology will really take off.”SKA should produce a wonderful Faraday grid,” Ensling said.

So far, the only magnetic evidence in the void is what the observer can’t see when he observes what is called the blaze variant behind the void.

Glare variants are gamma rays and other high-energy beams and bright beams of matter driven by supermassive black holes. As gamma rays propagate through space, they sometimes collide with ancient microwaves, thereby transforming into electrons and positrons. These particles then decay and become gamma rays with lower energy.

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However, Andri Nile of the Geneva Observatory in 2010 Andrii Neronov and Ievgen Vovk believe that if the light of the blaze variant passes through the magnetized void, it seems that it will lack low-energy gamma rays. The magnetic field deflects electrons and positrons into line of sight. When they decay into lower energy gamma rays, these gamma rays will not point to us.

It is true that when Nironov and Wulfke analyzed the data from the blaze variant in place, they saw their high-energy gamma rays, but could not see the low-energy gamma-ray signals. Vachappati said:”No signal is a signal.”

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No signal is hardly a smoking gun, and alternative explanations for missing gamma rays have been proposed. However, follow-up observations increasingly pointed to Nironov and Wulfke’s hypothesis that the void was magnetized. &34; This is the view of most people, &34; Duller said. Most convincingly, in 2015, a team superimposed many measurements of blaze variants behind the void and managed to find the faint low-energy gamma-ray halo around the void. If the particles are dispersed by a weak magnetic field, the effect is exactly what is expected-the magnetic field strength is only one ten thousandth of the refrigerator magnet.

The biggest mystery of cosmology

Surprisingly, the exact number of primitive magnetic fields may be the solution to the Hubble tension (universe Singular rapid expansion problem) required.

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This is how Bogosian saw Montpellier in France The computer simulation of Karsten Jedanzik and his collaborators at the University of Egypt was recently realized. The researchers added a weak magnetic field to the simulated young universe filled with plasma and found that the protons and electrons in the plasma flew along the magnetic field lines and gathered in the weakest magnetic field strength area. This clustering effect causes protons and electrons to combine to form hydrogen earlier (a type of early phase transition called recombination).

When reading the paper by Jadenzke, Bogozian found that this can solve the problem of Hubble tension. Cosmologists calculate the speed at which space should expand today by observing the ancient light emitted during the reorganization process. The light shows a young universe, covered with spots, which are formed by the sound waves sloshing in the original plasma.

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If the reorganization that occurs due to the aggregation effect of the magnetic field is greater than expected Early, then the sound waves may not travel that far, and the spots produced will be smaller. This means that the spots we see in the sky after the reorganization must be closer to us than the researchers thought. The light from the spots must travel a shorter distance to reach us, which means that the light must have been traversing the faster expanding space.”It’s like trying to run on an ever-expanding surface; you cover a shorter distance,” Bogosian said.

The result is that a smaller cluster of galaxies means a higher rate of inferred cosmic expansion—making the rate of inference closer to the measured value of the actual flying velocity of supernovae and other astronomical objects.

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&34; I think, wow, &34; Bogosian Say, &34; this may point us to the actual existence of the magnetic field. So I immediately wrote to Karsten. Just before the new crown was blocked, the two met in Montpellier in February. Their calculations show that the original magnetic force required to solve the Hubble tension problem is also consistent with the observations of bladder variants, and the estimated size of the original magnetic field is consistent with the size of the magnetic field required to grow a huge magnetic field that spans galaxy clusters and filamentary objects. &34; All of this fits perfectly, &34; Bogausian said, &34; however, this requires more facts to prove its correctness. &34;