Quasars are very faraway objects that radiate tremendous amounts of energy in a manner similar to that of stars.
They shine with a luminosity that is hundreds of billions of times greater than that of stars. It’s possible that these objects are black holes, which produce a tremendous amount of radiation whenever they consume stars or interstellar gas.
There are certain cosmological entities that do not produce the majority of their radiation in the form of visible light, and the region of the electromagnetic spectrum that contains the light that we sense is quite limited. Radio astronomers began to identify highly powerful radio sources that did not necessarily correspond to visible objects when they began their study of radio waves.
The phrase “quasi stellar radio source” is where the word “quasar” originates from.
How to identify quasars?
In the 1950s, they were recognized as such. It was later discovered that they exhibited a redshift that was greater than that of any other item that was known at the time. The Doppler effect, which shifts the spectrum toward the redder end when objects move further apart, was the root source of the problem.
The distance between Earth and the first quasar to be investigated, 3C 273, is 1.5 billion light-years. Since 1980, thousands upon thousands of quasars have been discovered. Some of them are receding from us at rates that are equivalent to 90 percent of the speed of light.
Quasars have been located at a distance of 12 billion light-years from our planet. This number is a rough estimate of the age of the universe. In spite of the vast distances involved, there is often a significant amount of energy that is received. As an illustration, s50014+81 has a luminosity that is approximately 60,000 times greater than that of the Milky Way.
The fact that quasars can be observed makes them all the more remarkable, despite the fact that they are so far away. If a quasar is located several billion light-years away, it has to be as brilliant as a thousand galaxies working together in order for it to be seen as a dim star.
But what’s even more incredible is the fact that this massive amount of energy originates from a location that’s no bigger than one light-year across (less than one hundred thousandth the size of a normal galaxy). Since the luminosity of quasars varies with periods of a few months, we may deduce that their size is far lower than the distance that light can travel in that amount of time.
At first, astronomers did not see any connection between quasars and galaxies. However, as scientists have found galaxies whose nucleus bears similarities to quasars, the gap between these two types of cosmic objects has gradually been filled.
It is now believed that quasars are the nuclei of extremely young galaxies. Activity in the nucleus of a galaxy lessens with the passage of time, but it does not vanish entirely.
Why are quasars important for the universe?
Astronomers are of the opinion that the vast majority of massive galaxies, if not all of them, went through a “quasar phase” in their younger years, not long after their creation. If this is the case, their luminosity began to decrease when the accretion disk that was around their supermassive black holes was unable to receive any more matter for their food supply.
After this period of time, galaxies went into a state of quiescence because the core black holes in them ran out of material to consume. However, observations have shown that the supermassive black hole at the heart of our galaxy occasionally emits radio waves and X-rays as material from the surrounding galaxy falls into its gravitational pull.
It is not out of the realm of possibility for a black hole to shatter whole stars and eat them as they pass through its event horizon, also known as the point of no return.
It is important to keep in mind, however, that our understanding of the progression of galaxies, from active young quasars to dormant middle-aged galaxies, is by no means comprehensive. There are exceptions to every rule, and if we want an illustration of this, we need not go any farther than the Milky Way in our own galaxy.
For instance, current knowledge tells us that our galaxy’s galactic core was the site of a massive explosion referred to as a Seyfert flare some 3.5 million years ago.
How far away are quasars?
But if it were entirely accurate that quasars were located as far out as the boundary of the observable universe, then it begs the question of how they were able to generate such massive amounts of energy. When 1964 rolled around, the very existence of black holes was a topic of heated discussion.
Many scientists regarded them as little more than mathematical oddities since they were certain that they could not actually exist in the universe as we know it.
It was not until the 1970s that a new generation of Earth-and space-based telescopes established beyond a shadow of a doubt that quasars do indeed lie at vast distances, that we were seeing galaxies when they were young, and that the quasar stage is a natural phase of their growth.
As a result, the discussion regarding the nature of quasars continued for quite some time. Astronomers have finally been able to model the identity of the almost incomprehensible powerhouse that lies behind quasars, which are supermassive black holes that consume stupendous amounts of gas and, as a result, radiate vast amounts of energy across the spectrum.
This was made possible by the fact that black holes were finally given the attention they deserved.
Because quasars are young galaxies, seen not long after their birth in the early universe, this explanation explains why quasars sit near the edge of the observable cosmos and why we don’t see them closer: because quasars are active galactic nuclei.