# Mysterious Quasars: What We Know & Don't Know

• gaugeboson
In summary, quasars can have a redshift factor of nearly 4, making them as old as the universe itself, with some being as old as 10% of the current age. They still exist today, but their numbers have decreased. The illusion of superluminal velocity in their 2 inner cores is due to relativistic and projection effects and not their actual speed.
gaugeboson
If we calculate the distance from us to the nearest quasar, it is huge with a redshift factor nearly equal to 4. Does that make them as old as the universe itself? Do they exist today? Also, why are their 2 inner cores expanding at superluminal velocities?

gaugeboson said:
If we calculate the distance from us to the nearest quasar, it is huge with a redshift factor nearly equal to 4.

The nearest quasar is much closer than that. Though it depends on the definition of "quasar", many would say that 3C 273 is the nearest, with a redshift z=0.173.

Does that make them as old as the universe itself?

Some quasars are nearly as old as the universe, yes. The highest redshift we've observed is around z=6, so at that time the universe was less than 10% of its current age.

Do they exist today?

Yes, though their numbers are greatly decreased. The peak of quasar activity was between redshifts of 2 and 3.

Also, why are their 2 inner cores expanding at superluminal velocities?

This is an illusion induced by a combination of relativistic and projection effects. We measure the angular velocities of quasar outflows and then use the distance to get the linear velocity. If you don't correct for emission delays due to the finite speed of light, then this can sometimes give you an outflow speed faster than c.

## What are quasars?

Quasars, also known as quasi-stellar objects, are extremely bright and distant objects in outer space. They are believed to be powered by supermassive black holes at the center of galaxies.

## How far away are quasars?

Quasars are located at incredible distances from Earth, ranging from millions to billions of light-years away. This means that the light we see from quasars has taken millions or even billions of years to reach us.

## Why are quasars mysterious?

Quasars are mysterious because they emit large amounts of energy and radiation, but their exact nature and mechanisms are still not fully understood. Scientists are still studying and learning about quasars to uncover their secrets.

## What do we know about quasars?

We know that quasars are incredibly bright, distant objects powered by supermassive black holes. They were first discovered in the 1960s and have been studied extensively since then. We also know that quasars can provide valuable information about the early universe and the formation of galaxies.

## What don't we know about quasars?

There are still many unanswered questions about quasars, such as how they are formed, how they produce such massive amounts of energy, and why they are so rare in the universe. Scientists are also trying to understand the relationship between quasars and their host galaxies.

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