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Pulsar emissions as they had never seen.
Captured images space observatory Chandra NASA have allowed us to study the dynamics of two pulsars with unprecedented detail. The result is crucial to refine models of many astrophysical phenomena. The Chandra space observatory NASA images have provided important new information on some of the most fascinating phenomena of the observable universe: pulsars, which as of headlights sweeping the cosmos with their energetic particle emissions.
Pulsars are a type of neutron star that is born from supernova explosions following the collapse of massive stars. Their peculiarity is to rotate rhythmically as they move in space at speeds that reach hundreds of kilometers per second. Initially discovered as beams of radio emissions, more recently they have also been associated with beams of high-energy gamma rays.
The problem is that rarely fit together the two types of bundles: The shapes of pulses observed in the spectrum range and radio are often very different from each other and some of the objects only show a pulse type and not the other. And this variability of events has generated a lively debate among astrophysicists on the possible nature of pulsars. One of the most accepted theory is that differences in the pulses are due mainly to the geometry of the pulsar, and in particular as they are oriented in their axis of rotation and the magnetic axis with respect to the observation line. In the case for example of nebulae generated by the wind of pulsar (pulsar wind nebulae, PWN), the expulsion of energetic particles occurs along the magnetic field lines of the star. These particles form a bull – that is a form three-dimensional donut-shaped – around the equatorial plane of the pulsar, and of the jets along the axis of rotation.
A spectacular cloud has been spotted around the pulsar Geminga. In addition to being the closest to us – is in fact just 800 light years from Earth – this cloud has three “tails” unusual. The first two are the particle beams that emerge from the hypothetical poles, and which extend for more than half a light year, that is more than 1000 times the distance between the Sun and Pluto, while the third has much more limited size.
The surrounding PSR B0355 + 54, is a very different cloud, that comes up with the pulsar covered with a sort of hat on one side and a double tail on the other, with an extension of almost five light-years from the star. Thanks to Chandra’s imaging capabilities we were able to reconstruct the three-dimensional structure of nebulae generated by the wind of the pulsar with unprecedented detail. Because of the combination of very intense magnetic fields and in rapid rotation, the pulsar are able to accelerate particles to high energy generating a wind whose interaction with the surrounding environment gives rise to a nebula synchrotron known as pulsar wind nebula. With observational advances in X-band, and the recent development of theoretical models in which the INAF researchers have contributed substantially, you can now enjoy high-resolution observations of the morphology of plerioni, to obtain information on the processes of acceleration of particles in pulsar: the structure of their magnetic field, the composition of the wind, the acceleration efficiency, and so on. Since pulsars, it was generally considered a prototype of a cosmic accelerator, the opportunity to study in detail the properties of particle flows generated by them is crucial to check the validity of the theoretical models, often applied to other astrophysical phenomena.
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