Pulsars: Cosmic Lighthouses

Pulsars aren’t actually stars or at least not “alive” stars. Pulsars are members of the neutron star family, which form when a star with a mass greater than the sun runs out of fuel in its core and collapses in on itself. Neutron stars are normally 12.4 to 14.9 miles (20 to 24 kilometers) in diameter, but they can have up to twice the mass of the sun, which has a diameter of 864,938 miles (1.392 million km). This type of star death usually results in a tremendous explosion known as a supernova. The dense nugget of material left over after this cataclysmic death is the neutron star. Pulsars actually appear as flickering stars on earth as they flicker in a steady rhythm.

Pulsar: 

Pulsars are spheres, dense objects, the size of a large city yet with a mass greater than the sun. Two narrow, constant beams of light that are emitted by the pulsars travel in opposite directions. Pulsars appear to flicker despite the fact that the light from the beam is constant. It’s the same reason why a lighthouse on the water looks to blink when seen by a sailor. The pulsar’s light beam may sweep across the Earth, then swing out of view, then swing back around again as it revolves. 

The light comes in and out of the vision of an astronomer on the ground, giving the impression that the pulsar is flashing on and off. The light beam of a pulsar spins around like a lighthouse beam because the pulsar’s axis of rotation is usually not aligned with the pulsar’s axis of rotation.

Discovery of Pulsars: 

Jocelyn Bell and Anthony Hewish were investigating the stars at the Cambridge Observatory in 1967 when they discovered something unusual. It appeared to be a star-like object producing rapid radio wave pulses. For a long time, radio sources had been known to exist in space. 

But this was the first time anyone had seen anything emit such rapid pulses. They pulsated exactly once per second, like clockwork. Initially, the signal was considered to be coming from an orbiting satellite, but this theory was rapidly debunked. Because of their rapidly pulsing characteristics, these objects were given the name pulsars after numerous more were discovered.

The spinning phenomenon of Pulsars: 

Pulsars spin at a high rate, up to 20 times per second. Scientists believe the spin was created by the conservation of angular momentum from a spinning star prior to its explosion. However, scientists had no idea if the stars that produced the pulsars were spinning at all, but it was later determined that the spin of a pulsar is caused by the explosion itself, not by whether or not the star that created it was spinning.

Radiation by Pulsars: 

Pulsars can emit light in a variety of wavelengths, from radio waves to gamma-rays, the universe’s most energetic kind of light. Radio waves make up the lighthouse-like beams of light that scientists first noticed in the 1960s. These light beams are famous for being exceedingly brilliant and narrow, with qualities that are similar to those of a laser beam.  Gamma-rays are emitted at a different altitude above the surface and from a different location in the space surrounding the pulsar than radio waves.

Lighthouse Effect of Pulsars: 

We detect radio waves every time one of the poles rotates into our line of sight if the neutron star is oriented so that the poles face the Earth. The effect is similar to that of a lighthouse. A stationary spectator will see that the lighthouse’s light blinks on and off as it spins. 

Similarly, as its revolving poles sweep past the Earth, the pulsar appears to blink. Depending on the size and mass of the neutron star, different pulsars pulse at varying rates. A binary companion to a pulsar is possible. The pulsar may begin to attract matter from this partner in some situations. This could make the pulsar spin even faster. Pulsars that are the fastest can pulse over a hundred times per second.

Finding Pulsars: 

Large radio telescopes are still used to find pulsars nowadays. Arecibo, Puerto Rico, is home to the world’s largest radio telescope. It’s been an important instrument in the hunt for pulsars. In recent years, several new pulsars have been identified. A pulsar can be found inside the renowned Crab Nebula (M1). 

A new radio telescope technology known as a multibeam receiver system was recently used in Australia to discover the 1000th pulsar. This device allows radio telescopes to scan the skies simultaneously with up to 13 beams. New pulsars are discovered ten times faster today than they were in the 1970s and 1980s.

Conclusion: 

Pulsars are celestial phenomena that appear to emit very regular radio waves pulses. A handful emits visible light, X-rays, and gamma radiation in short rhythmic bursts. Because these do not line up with the pulsar’s own axis of rotation, the radiation beams swing around like lighthouse beams as the star spins, producing pulses.