They detect a powerful ‘jet’ of matter and antimatter emitted by a pulsar 1,600 light-years from Earth
A team of researchers from the California Institute of Technology in Pasadena has just published the image of a huge filament, a jet of matter and antimatter more than 60 billion km long. The beam, the largest of its kind ever seen, comes from a pulsar, the compact core of an ancient collapsed star that rotates very rapidly and has a strong magnetic field. The work may help to unravel a mystery that has baffled scientists for decades Scientists: Where does all the antimatter that astronomers see in our galaxy come from?
Researchers first discovered this huge structure in 2020, but they didn’t know its full length because it extended beyond the edge of the Chandra detector, the telescope with which the observations were made.
But the same two researchers tried again in February and November 2021 and, this time, they found that the filament is about three times longer than what was seen in the first observation. The filament spans about half the diameter of the Full Moon in the sky, making it the longest a pulsar seen from Earth. The work has just been published in ‘ The Astrophysical Journal ‘.
“It is surprising that a pulsar only 15 km in diameter can create such a large structure that we can see it from thousands of light-years away,” says Martijn de Vries, who led the study. With the same relative size, if the filament stretched from New York to Los Angeles, the pulsar would be about 100 times smaller than the smallest object visible to the naked eye.”
The pulsar in question is called PSR J2030+4415 and is located about 1,600 light-years from Earth. This object, the size of a city, rotates about three times per second.
The antimatter problem
Except for their electrical charge, which is opposite, matter and antimatter are identical in all respects. And as physicists know very well, in nature all particles have their corresponding ‘antiparticles’. Thus, an ‘antielectron’ or positron corresponds to an electron, which is nothing more than an electron with a positive charge, just as each proton has its antiproton and each neutrino, to name just a few examples, its antineutrino. It so happens that when a particle of matter meets its corresponding antiparticle (for example, an electron meets a positron), both are destroyed in a flash of energy.
According to current theory, an identical amount of matter and antimatter should have been generated during the Big Bang. But there is countless evidence that everything we can see around us, even the most distant of galaxies, is made only of matter. As far as we know, there are no ‘anti-planets’ or ‘anti-stars’ up there. And if they did exist, we would certainly have already detected the high-energy gamma flashes resulting from their contact with the ‘normal’ matter around them.
Where, then, is all the missing antimatter? Finding out how we ended up in a Universe full of matter and virtually no trace of antimatter is one of the biggest mysteries facing Physics.
Which, however, does not mean that scientists still occasionally find evidence of relatively large numbers of antimatter particles (especially positrons) with their detectors. But what are the sources of this antimatter?
A source of antimatter
The study authors believe they have found an answer. The antimatter we see in the galaxy comes from pulsars like PSR J2030+441. In them, the combination of rapid rotation and very intense magnetic fields accelerate the particles and create beams of high-energy radiation that give rise to pairs of electrons and positrons. Pulsars then launch these positrons, through beams like the one the authors of this study have photographed, throughout the galaxy.
The mechanism, however, is not so simple. Pulsars are known to generate ‘winds’ of charged particles, which are normally confined within their powerful magnetic fields. PSR J2030+441 is traveling through interstellar space at approximately 1.5 million km per hour, with the wind behind it. A discharge of gas moves in front of the pulsar, somewhat like the pooling of water in front of a moving ship. However, about 20 to 30 years ago, the motion of the bow shock seems to have stopped, so the pulsar caught up with it. This resulted in an interaction with the interstellar magnetic field moving almost in a straight line from left to right.
“This probably triggered a particle leak,” explains Roger Romani, co-author of the study. The magnetic field of the pulsar wind linked up with the interstellar magnetic field, and high-energy electrons and positrons spurted out through a ‘nozzle’ formed by the connection.”
As the particles moved along the interstellar magnetic field line at about one-third the speed of light, they illuminated it in X-rays. And that produced the long filament scientists observed. A complex mechanism, but one that could explain the presence of antimatter in the
A team of researchers from the California Institute of Technology in Pasadena has just published the image of a huge filament, a jet of matter and antimatter more than 60 billion km long. The beam, the largest of its kind ever seen, comes from a pulsar, the compact core of an ancient collapsed star that rotates very rapidly and has a strong magnetic field. The work may help to unravel a mystery that has baffled scientists for decades Scientists: Where does all the antimatter that astronomers see in our galaxy come from?
Researchers first discovered this huge structure in 2020, but they didn’t know its full length because it extended beyond the edge of the Chandra detector, the telescope with which the observations were made.
But the same two researchers tried again in February and November 2021 and, this time, they found that the filament is about three times longer than what was seen in the first observation. The filament spans about half the diameter of the Full Moon in the sky, making it the longest a pulsar seen from Earth. The work has just been published in ‘ The Astrophysical Journal ‘.
“It is surprising that a pulsar only 15 km in diameter can create such a large structure that we can see it from thousands of light-years away,” says Martijn de Vries, who led the study. With the same relative size, if the filament stretched from New York to Los Angeles, the pulsar would be about 100 times smaller than the smallest object visible to the naked eye.”
The pulsar in question is called PSR J2030+4415 and is located about 1,600 light-years from Earth. This object, the size of a city, rotates about three times per second.
The antimatter problem
Except for their electrical charge, which is opposite, matter and antimatter are identical in all respects. And as physicists know very well, in nature all particles have their corresponding ‘antiparticles’. Thus, an ‘antielectron’ or positron corresponds to an electron, which is nothing more than an electron with a positive charge, just as each proton has its antiproton and each neutrino, to name just a few examples, its antineutrino. It so happens that when a particle of matter meets its corresponding antiparticle (for example, an electron meets a positron), both are destroyed in a flash of energy.
According to current theory, an identical amount of matter and antimatter should have been generated during the Big Bang. But there is countless evidence that everything we can see around us, even the most distant of galaxies, is made only of matter. As far as we know, there are no ‘anti-planets’ or ‘anti-stars’ up there. And if they did exist, we would certainly have already detected the high-energy gamma flashes resulting from their contact with the ‘normal’ matter around them.
Where, then, is all the missing antimatter? Finding out how we ended up in a Universe full of matter and virtually no trace of antimatter is one of the biggest mysteries facing Physics.
Which, however, does not mean that scientists still occasionally find evidence of relatively large numbers of antimatter particles (especially positrons) with their detectors. But what are the sources of this antimatter?
A source of antimatter
The study authors believe they have found an answer. The antimatter we see in the galaxy comes from pulsars like PSR J2030+441. In them, the combination of rapid rotation and very intense magnetic fields accelerate the particles and create beams of high-energy radiation that give rise to pairs of electrons and positrons. Pulsars then launch these positrons, through beams like the one the authors of this study have photographed, throughout the galaxy.
The mechanism, however, is not so simple. Pulsars are known to generate ‘winds’ of charged particles, which are normally confined within their powerful magnetic fields. PSR J2030+441 is traveling through interstellar space at approximately 1.5 million km per hour, with the wind behind it. A discharge of gas moves in front of the pulsar, somewhat like the pooling of water in front of a moving ship. However, about 20 to 30 years ago, the motion of the bow shock seems to have stopped, so the pulsar caught up with it. This resulted in an interaction with the interstellar magnetic field moving almost in a straight line from left to right.
“This probably triggered a particle leak,” explains Roger Romani, co-author of the study. The magnetic field of the pulsar wind linked up with the interstellar magnetic field, and high-energy electrons and positrons spurted out through a ‘nozzle’ formed by the connection.”
As the particles moved along the interstellar magnetic field line at about one-third the speed of light, they illuminated it in X-rays. And that produced the long filament scientists observed. A complex mechanism, but one that could explain the presence of antimatter in the Milky Way.
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