Ultrarsions

1989/12/01 Arregi Bengoa, Jesus Iturria: Elhuyar aldizkaria

• Astronomia

Last March J. In a work signed by Kristia and his collaborators, the detection of the pulsation network that was believed to emerge as a result of the birth of the supernova (the SN 1987 A supernova) that occurred two years ago in the Great Magellanic Cloud. Astronomers eagerly hoped that this discovery could be a very important contribution to the theory of pular formation. However, the aforementioned work provides a data that questions this statement; an important fact that has not calmed scientists and has generated new debates.

This peculiarity is the turning speed of the network: 2000 %. On the contrary, astronomers only expected ten or a hundred hertz. The given value is much higher than that of the pulsations mentioned in the title and analyzed immediately. In the next issue we will analyze in depth the problems it generates, but before, as we have said, we will talk about those other rapid pulsars to enter the subject.

The pulse network of Karramarro Nebulosa has its origin in the supernova of the year 1054.

The most precise reference for comparing the speeds of the bracelets is the one found in the Crab Nebula, since its age is known (created by the 1054 supernova). Its speed is around 33 hertz and is decreasing progressively. This braking is a consequence of the energy emission. As is known, pulses that call the net (pulsating star) are produced by the strong magnetic field of the neutron star resulting from the supernova due to its rapid rotation.

Therefore, the emission is made at the cost of the spinning movement, so its speed is decreasing. Normally that crab is usually astirous. That is why we said that the speed of the first pulse was expected to be about ten or a hundred hertz. Until 1982 this picture was totally coherent. The pulse net of the Crab Nebula was the fastest and supposedly the youngest. But from then on there have been found pulsation networks of higher turning speed and it cannot be admitted that they are younger. It has already been tried to give explanations for this group, but also the fastest (barely 700 hertz) does not approach the SN 1987-A. Let's understand what these explanations consist of.

The high speed swing pulses (some hundreds of hertz) usually have another remarkable feature: an extremely low braking value. This means that they lose the spinning energy very slowly. Therefore, the magnetic field, which causes loss, is small. Faced with this, some astrophysicists claim that the pulsions of this group can be formed in different conditions of creation. For example, under low magnetic field conditions, so they would keep the fast turning for a long time. However, they do not offer great details about the conditions of creation.

Others, for their part, propose that these pulsars accelerate again after a great slow down. The idea is based on double X-ray emitting systems. It is believed that these systems are formed by a neutron star and another current, and the emission occurs when falling and stacking (by friction) the matter that the neutron star takes away by spinning around the other star. These propose, therefore, that ultra-fast pulsars would be of the oldest. Hundreds of millions of years later would turn slowly and as the magnetic field also weakened would not emit radiation. Some of these fleas could run over another star, and the matter that would fall from that other one would bring to the net the energy of its movement, thus recovering it.

If this last hypothesis is correct, the ultra-fast pulse should be more abundant in globular clusters. Stellar density is enormous, as thousands of stars accumulate in a sphere the size of the Solar System. Therefore, the probability of capturing a star is much higher. In it, moreover, the number of neutron stars is quite high. The globular clusters, being outside the galaxy plane, have had a fairly independent evolution, reaching the final phase of life with many stars and in many cases with neutron stars. The first positive results have been the studies of some clusters and more elements of the type of bracelet have been found that concern us, but not all in double systems. It seems to be borne in mind that high density of stars can break systems through shocks.

There are still some points that are not clear in this theory, but that indirectly offer an alternative of analysis. The braking of these fleas is extremely heavy, so their period is more constant than the atomic clocks we have on Earth. Therefore, the effects produced by the stars that can pass through the surroundings would be significant, since these effects would give us a direct information of the density of the cluster. Finally, we will say that some observatories have already programmed programs of detection and systematic analysis of pulsions in the clusters.