In 1967 the first pulsar was discovered, a neutron star that causes this phenomenon of intermittent light: what it is, what is its origin and how it acts.
Pulsars are neutron stars that emit radio signals at short and regular intervals. The abbreviated term pulsar comes from pulsating radio source, or pulsating star. The first pulsar was discovered by chance in 1967, and its intermittent signals were initially taken for radio signals of extraterrestrials! It is, instead, a phenomenon caused by the extremely high speed of rotation of the pulsating star, which produces radiation towards its magnetic axis. When the rotational and magnetic axes do not converge, the radiation flux is visible on Earth, just like the powerful light of a lighthouse.
A small lighthouse seen from Earth: that's what pulsars are
So what is a pulsar? Pulsars are very dense and compact stars that are about the size of a large city but contain more mass than the sun. They are highly magnetized spherical rotating elements, usually neutron stars but also white dwarfs, that emit beams of electromagnetic radiation from their magnetic poles.
Neutron stars have short, regular rotation periods. This produces a very precise interval between pulses, ranging from milliseconds to seconds for a single pulsar. This radiation can only be observed when an emission beam points toward Earth. As we said at the beginning, we can compare it to the way a lighthouse can only be seen when the light is pointed in the direction of an observer.
Viewed from Earth, pulsars appear as blinking stars, cones of yellow light that turn on and off regularly. In reality, this happens because the pulsar's light beam is usually not aligned with the pulsar's axis of rotation. The frequency of the light pulses also reveals how fast the pulsar is rotating.
In total, more than 2,000 pulsars have been detected. Most of these, rotate on the order of once per second (these are the so-called "slow pulsars"), while more than 200 pulsars have been found rotating hundreds of times per second (called "millisecond pulsars"). The fastest known millisecond pulsars can rotate more than 700 times per second!
What origin do pulsars have
A pulsar is not really a star, or at least it is not a "living" star. As mentioned earlier, the pulsar belongs to the family of "neutron stars" that are formed when a star more massive than the Sun runs out of fuel in its core and collapses in on itself. This stellar death typically creates a massive explosion called a supernova. The neutron star is the dense nugget of material left over after this explosive death.
Pulsars: some characteristics
Neutron stars are typically 12.4 to 14.9 miles (20 to 24 kilometers) in diameter, but they can contain up to twice the mass of the Sun, which has a diameter of about 864,938 miles (1.392 million km). A lump-sized piece of material from a neutron star would weigh about 1 billion tons (0.9 metric tons), "about the same as Mount Everest," according to NASA.
The gravitational pull on the surface of a neutron star would be about 1 billion times stronger than the gravitational pull on the surface of Earth. The only object with a density greater than a neutron star is a black hole, which also forms when a dying star collapses.
The most massive neutron star ever measured is 2.04 times the mass of the Sun. According to Feryal Özel, a professor of astronomy and astrophysics at Arizona State University who specializes in compact objects and extreme states of matter in the universe, scientists don't know exactly how massive neutron stars can become before they become black holes.
Özel also pointed out that the radio wave beam emitted by a pulsar may not pass through the field of view of an Earth-based telescope, preventing astronomers from seeing it. Why do pulsars have a wavelike motion? Pulsars rotate because the stars from which they formed also rotate, and the collapse of stellar material leads to an increase in the pulsar's rotational speed.
The pulsar absorbs matter and momentum from other celestial bodies, gradually increasing its rotational speed. In practice, a pulsar can completely swallow a star and suck the life out of it! For years pulsars continue to fascinate the scientific community and are still being studied, used by scientists for information on the physics of neutron stars that are the densest material in the universe (except for the matter of black holes), but are also studied for the search for planets beyond the Earth's solar system and to measure cosmic distances. Pulsars could also help scientists in analyzing gravitational waves, which could point the way about energetic cosmic events such as collisions between supermassive black holes.