Universe

Pulsars

Pulsars

The Pulsars they are sources of radio waves that vibrate with regular periods. They are detected by radio telescopes.

The word Press It is an acronym for "pulsating radio source", a pulsating radio source. Clocks of extraordinary precision are required to detect rhythm changes, and only in some cases.

Studies indicate that a pulsar is a small neutron star that spins at high speed. The best known is in the Crab Nebula. Its density is so great that, in them, the matter of the measurement of a ball pen has a mass of about 100,000 tons. They emit a lot of energy.

The magnetic field, very intense, is concentrated in a small space. This speeds it up and makes it emit a beam of radiation that, here, we receive as radio waves through radio telescopes.

The pulsars were discovered in 1967 by Anthony Hewish and Jocelyn Bell at the radio astronomy observatory in Cambridge. Many pulsating stars are known, but only two, the Pulsar of the Crab, and the Pulsar of the Candle, emit visible detectable pulses. It is known that these two also emit gamma-ray pulses, and one, the Crab's, also emits X-ray pulses.

The regularity of the pulses is phenomenal: observers can now predict the arrival times of the pulses in advance of one year, with an accuracy better than a millisecond.

Pulsators are strongly magnetized neutron stars. The rapid rotation, therefore, makes them powerful electric generators, capable of accelerating charged particles to energies of one billion Volts.

These charged particles are responsible for the radiation beam in radio, light, X-rays, and gamma rays. Its energy comes from the rotation of the star, which therefore has to be slowing down. This decrease in speed can be detected as an extension of the pulse period.

Where are the pulsars?

Pulsars have been found mainly in the Milky Way. Full scrutiny is impossible, since weak pulsars can only be detected if they are close.

Radio polls have already covered most of the sky. Their distances can be measured from a delay in the arrival times of the pulses observed in the low radio frequencies; the delay depends on the density of the electrons in the interstellar gas, and the distance traveled.

Extrapolating from this small sample of detectable pulsars, it is estimated that there are at least 200,000 pulsars throughout our Galaxy. Considering those pulsars whose beacon beams do not sweep in our direction, the total population should reach one million.

Each pulse emits for about four million years; After this time he has lost so much rotational energy that he cannot produce detectable radio pulses. If we know the total population (1,000,000), and the life time (4,000,000 years), we can deduce that a new pulse must be born every four years, assuming that the population remains stable.

Recently pulsars have been found in globular clusters. It is thought that they have been formed there by the accretion of matter in white dwarf stars that are part of binary systems.

Other pulsars are born in supernova explosions. If all the pulsars were born in supernova explosions, we could predict that there should be a supernova in our Galaxy every four years, but this is not yet clear.

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