Sunday, January 24, 2021, 07:06
In 1967, Jocelyn Bell, an astrophysical doctoral student at the University of Cambridge, studied with a special detector built by her thesis director, professor Antony Hewish, distant sources of electromagnetic emissions, in particular in the reach of radio frequency. With his experimental team in the direction of the constellation of Vulpecula, he detected a fast, intense and fully regular radio pulses source. He received them every 1.33 seconds. When he saw this regularity, the RadioStronomos considered the possibility that it was signals of an intelligent and, half -Joke in a medium seriously, called the LGM source (‘Little Green Men’). Soon similar signs were found in other directions of the room (currently 2500) with times between successive pulses, between a thousandth seconds and 10 seconds. They forgot LGM and they were called pulsars (‘pulsating radio sources’ fuentes pressed the radio). The Nobel Committee has awarded its prize to Hewish and Ryle and left the PhD student who discovered the pulses for the first time.
Later, a pulsars of many wavelengths were discovered in the middle of a gas cloud (scratching), the remnant of a Supernova that exploded a thousand years ago, which is emitted an energy -broadcast one hundred thousand times larger than the sun is emitted. That meant that these signals could be emitted by the elusive neutron stars. Stars consisting of 95%neutrons, along with a small amount of protons and electrons and an outer layer of normal materials (iron, etc.). The diameter is very small, between ten and twenty kilometers and, since the masses are very large, they are the closest objects of the universe (one hundred billion grams per cubic centimeter) with gravity on the surface a hundred billion times that of the earth.
Pulsars is the electromagnetic emission produced by a neutron star that runs at high speed around its axis. The effect is similar to that of a lighthouse that broadcasts a flash in every full rotation. What is the reason for the star to emit electromagnetic signals? The magnetic field of a star experiences a very high compression when the star collapses in one of neutrons. This field has, just like on earth, its two posts and surrounds the star. Protons and superficial electrons are caught in this rotating magnetic field and accelerated with almost the speed of light. In addition, part of the rotation energy of the magnetic field is converted into electromagnetic radiation that is only emitted by the two magnetic poles. That is why radiation reaches the earth when its position is in the emission address. Moreover, to understand the similarity with the lighthouse, the rotary axle of the star almost never coincides, contrary to what is happening on earth, with the direction of the magnetic axis. The pulsars are excellent natural laboratories of the universe and very exact watches.
