Quasar vs Blazar (A Comparison and Other FAQs)

Are you confused about the difference between a quasar and a blazar? Do you have some unanswered questions about these luminous phenomena?

This article will provide a description of quasars and blazars, and further highlight where they differ.

We will compare the two objects and answer some frequently asked questions surrounding the topic to help you fully understand the subject. 

Quasar vs Blazar: Explained


Quasars and blazars are both luminous astronomical objects powered by black holes in their core. The difference between the two is simply the angle in which they face. Quasars and blazars are formed when a supermassive black hole has enough material around it falling into the accretion disc to generate sufficient energy to power them. The only galaxies that have enough of such materials are young or colliding galaxies. 

What Is a Quasar?

A quasar is a highly luminous object found in the centre of some galaxies.

It is powered by gas spiraling at intense velocity into a supermassive black hole.

Quasars are amongst the most distant known astronomical objects, their luminosity can outshine all of the stars in the galaxy they reside in, making them visible at distances of billions of light-years.

Quasars are not stars, rather they are young galaxies located at vast distances away from us.

Quasars are highly active and emit staggering amounts of radiation across the entire electromagnetic spectrum.

There is another name for these extremely luminous centers of infant galaxies, known as ‘active galactic nucleus’ (AGN).

There are many different types of AGN, each releasing an intense amount of radiation that powers a massive black hole at its core.

The radiation is created from superheated material in the accretion disk generated by particles of dust, gas, and other matter.

What Is a Blazar?

A blazar is the same thing as a quasar, just at a different angle.

A quasar will be angled slightly towards the earth, whereas a blazar is angled directly towards the earth.

In other words, we’re looking straight down the barrel of the gun. 

Some AGN shoot out colossal jets of material that can travel close to the speed of light.

With a blazar, the earth is directly in the firing line, if close enough.

There is also another AGM called radio galaxy, which is angled straight up and never poses a risk to the earth.

Nonetheless, the nearest blazar, Markian 421, is 2.5 billion light-years away.

In the beginning, when blazars, radio galaxies, and quasars were first discovered, they were thought to be different objects.

We now know that they are the same. 

Quasar vs. Blazar – A Comparison

  • The closest blazar is 2.5 billion light-years away from the earth, whereas the nearest quasar is 600 million light-years away. 
  • Blazars and quasars are not stars, rather they are infant galaxies. 
  • The most distant quasar is 13.03 billion light-years away, hosting a supermassive black hole. The most distant blazar detected is 13 billion light-years away from the earth. 
  • The Milky Way is thought to have once hosted a quasar, but it has long been silent.
  • Blazars are much rarer than quasars. As of 2020, more than 750,000 quasars have been found. However, only 66 blazars have been identified. 
  • The brightest quasar has a maximum absolute magnitude of -26.7, whereas the brightest blazar has a maximum absolute magnitude of -31.4, making them one of the brightest gamma-ray sources in the sky.

How Quasars Were Discovered

The first discoveries of quasars were in the late 1950s using radio telescopes.

At the time, astronomers assumed that what they were seeing were star-like objects within our galaxy, yet somehow they weren’t visible in optical telescopes.

It puzzled astronomers why these stars were only detectable through radio instruments. 

It wasn’t until the early 1960s that the actual location, and therefore distance, of this star-like object was discovered, explaining why optical counterparts weren’t visible through the eyes of a telescope. It was simply too far away.

But still, they could not decipher what the object was. 

Using a hale telescope, they discovered that this ‘blue star’ was in fact quasar 3C273 passing behind the moon.

They continued on to find other quasars with what appeared to be strange emission lines. 

After further observations, it was found that these nonsensical lines were actually normal emission lines highly shifted towards the red end of the electromagnetic spectrum.

Why Are Quasars So Bright?

Quasars shine as brightly as they do because of the matter that they devour.

The matter is forced apart, stretched, torn into bits, and accelerated by the undefiable force of gravity.

The matter interacts with other bits of matter, heats up, and produces so much energy as it has no choice but to emit radiation. 

Quasars can emit trillions of electron volts.

This energy exceeds the light of all stars within a galaxy, totaled.

A quasar can shine as bright as 10 to 100,000 times the Milky Way, hence why they are the brightest objects in the universe.

Where Is The Nearest Quasar?

The nearest quasar to the earth is Markarian 231 at approximately 581 million light-years away.

Markarian 231 hosts two black holes in its center, furiously whirling around each other.

This is a common occurrence if one orbit falls into another.

It is believed that the second black hole was caused by a smaller galaxy merging into it. 


A quasar and a blazar are actually the same thing, except that a quasar is angled slightly towards the earth, whereas a blazar is angled directly towards the earth.

There is another AGN of the same properties called a radio galaxy which is angled straight up, and therefore will not omit anywhere near the earth. 

Quasars and blazars are so bright, yet so far away that their discovery puzzled astronomers for many years.

What at first were thought to be star-like objects, were found to be intensely luminous radiation emits formed by black holes.

There are only two galaxies with enough matter capable of forming such objects; these are young galaxies and colliding galaxies.

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Quasar vs Blazar

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