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A new computer model reveals the invisible and often bizarre behaviors of circulating particles around rapidly rotating neutron stars, also called pulsars.
A new study conducted by NASA astrophysicist Gabriele Brambilla shows the paths taken by charged particles captured in the magnetic and electric fields near the pulsars. The work is based on a new method of pulsar modeling and offers an unprecedented insight into the inner workings of these exotic celestial formations.
Pulsars are the collapsed remains of massive stars that ran out of fuel, collapsed and then exploded as a supernova. These swirling neutron stars carry a dreadful mass in a small space; A typical pulsar is about the size of Manhattan, but its mass is greater than that of the Sun. When they turn, often a thousand times per second, they exert the most powerful magnetic fields known to astrophysicists. At the same time, powerful electric fields tear the particles off the surface of the neutron star, throwing them into space. From Earth, we can see the rotating beam of gamma rays and radio pulses from a pulsar at extremely regular intervals – an effect often compared to the pulsed beam of the beacon beacon.
The pulsars look like gigantic particle accelerator experiments floating in space and produce a frightening physics, both at the micro and macro scale. Astronomers have been studying pulsars for over 50 years, but they are still unable to fully explain what they observe. Needless to say, we can not create these extreme conditions on the Earth, and we can not observe these objects closely, the closest of which is about 770 light years from Earth. This is why Brambilla and his colleagues turned to computer models to learn more about pulsars and their impact on the behavior of charged particles.
For the new study, published this week in Astrophysical Journal, scientists have turned to a relatively new method of modeling pulsars: a simulation system called PIC, or particle in a cell.
"The PIC technique allows us to explore the pulsar from the first principles. We start with a rotating magnetized pulsar, we inject electrons and positrons on the surface, and then we follow their interaction with the fields and their path, "said Constantinos Kalapotharakos, co-author of the study and scientist at Goddard Space Flight Center of NASA. , said in a statement. "The process is very computationally intensive because particle motions affect electric and magnetic fields and fields affect particles, and everything moves at a speed close to that of light."
The PIC simulation was conducted on two NASA supercomputers: the Discover supercomputer from NASA's Center for Climate Simulation and the Pleiades supercomputer from the Ames Research Center in California. Incredibly, the PIC model follows the movement of each particle, which collectively represents billions of electrons and their anti-matter counterparts, positrons them.
The new computer simulation showed particle movements never before studied by scientists. For example, researchers have observed most electrons moving away from magnetic poles in the pulsar. Meanwhile, positrons were flying at low altitude, forming thin structures called the "current sheet".
A NASA press release explains some of the other observations made in the study:
Some of these particles are likely to become extremely powerful at the points of the current sheet where the magnetic field is reconnected, a process that converts stored magnetic energy into heat and particle acceleration.
A population of medium energy electrons exhibited a truly strange behavior, scattering in all directions, even towards the pulsar.
The particles move with the magnetic field, which recedes and expands outward as the pulsar rotates. Their speed of rotation increases with distance, but it can not last so long, because the matter can not travel at the speed of light.
The distance at which the speed of rotation of the plasma reaches the speed of light is a feature that astronomers call the light cylinder and marks a region of sudden change. When the electrons approach it, they suddenly slow down and many disperse wildly. Others can slide behind the cylinder of light and go out into space.
If that sounds a bit cryptic, I highly recommend you look at the visual simulation (shown in the video above) produced by NASA Goddard, which pretty much illustrates these processes.
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It's easy to understand why physicists are so enthusiastic about pulsars, but SETI's astrobiologists and scientists can also find them useful. Research published last year has suggested that advanced extraterrestrials are more likely to build energy gathering megastructures around pulsars than ordinary stars. The reason is that pulsars concentrate their energy into discrete beams, as opposed to scattering them in all directions, as most stars do.
Anyhoo, Brambilla, his colleagues hope to perform other pulsar simulations to deepen their understanding of their intense magnetospheres and how pulsars may differ from each other.
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