Pulsar vs Quasar [The Definitive Comparison]

The cosmos, in all its vastness and intricacy, presents us with a myriad of celestial bodies, each with its unique attributes and phenomena.

Among these, pulsars and quasars hold a special interest for astronomers due to their unique properties and behaviors.

But how do they differ, and what do they have in common?

Let’s delve into the specifics.

What Is A Pulsar?

A pulsar is a highly magnetized, rapidly spinning neutron star that emits beams of electromagnetic radiation out of its magnetic poles. The term ‘pulsar’ stems from the ‘pulses’ of radiation that we detect as the star spins and its beams sweep past Earth, much like the beam of a lighthouse.


Pulsars are remnants of supernovae, the catastrophic explosions that end the life cycle of massive stars.

The core of such a star collapses under its own gravity, and the outer layers are blown away, leaving behind a compact, dense object composed almost entirely of neutrons.

The resulting neutron star is only about 20 kilometers in diameter, but it carries up to twice the mass of our sun.

The intense gravitational field of a neutron star, combined with its rapid rotation and a powerful magnetic field, generates the beams of radiation that define a pulsar.

These beams can include radio waves, visible light, X-rays, and even gamma rays, making pulsars some of the most energetic objects in the universe.

What Is A Quasar?

Quasars are active galactic nuclei – the extremely bright centers of distant galaxies. The term ‘quasar’ is short for ‘quasi-stellar radio source’ because they were initially mistaken for stars due to their star-like appearance. However, quasars outshine even the most luminous stars.


Quasars are fueled by supermassive black holes at the center of galaxies.

As matter from the surrounding galaxy falls into these black holes, it forms an accretion disk – a swirling mass of gas and dust heated to incredible temperatures.

The friction and gravitational energy of this disk generate enormous amounts of radiation, which can be seen across vast distances, even from the edge of the observable universe.

In contrast to pulsars, which are localized objects within a galaxy, quasars are cosmic lighthouses that mark the centers of galaxies and are powerful enough to outshine all the stars in their host galaxies combined.

What Is The Difference Between a Pulsar and a Quasar?

The primary differences between pulsars and quasars lie in their nature, size, and the phenomena they represent.


A pulsar, being a neutron star, is a stellar object with a physical size comparable to a city but with a mass greater than the sun.

On the contrary, a quasar denotes the activity in the core of a galaxy, powered by a supermassive black hole millions to billions of times the mass of the sun.

Energy Source

Secondly, the energy source for these objects is different.

Pulsars derive their energy from the rotation and the intense magnetic field of a neutron star, while quasars get their energy from the accretion disk surrounding a supermassive black hole, which releases vast amounts of radiation as matter falls into it.

Type Of Radiation Emitted

Lastly, the type of radiation they emit varies.

Pulsars are renowned for their radio waves and can emit light across the spectrum, but quasars are extraordinarily luminous across all wavelengths, including the radio, optical, ultraviolet, and X-ray bands.

Do Pulsars and Quasars Share Any Similarities?

Despite their differences, pulsars and quasars do share some intriguing similarities.

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Firstly, both are extreme objects powered by gravity – pulsars by the collapse of a stellar core into a neutron star, and quasars by the gravitational pull of supermassive black holes.

They Emit Radiation

Secondly, both pulsars and quasars emit highly energetic beams of radiation, although they do this in different ways.

Pulsars emit their beams from their magnetic poles, while the radiation from quasars comes from the accretion disk around a black hole.

Celestial Bodies For Research

Finally, both types of objects are valuable tools for astronomers.

Pulsars, with their precise periodic signals, are used to test theories of gravity and study the interstellar medium.

Quasars, visible at the greatest distances, help us to understand the early universe and the evolution of galaxies.


While pulsars and quasars might be fundamentally different, each offers unique insights into the mechanisms that drive the universe, from the life cycles of stars to the behaviors of galaxies.

As such, both remain subjects of avid study for astronomers worldwide.