Updated: Aug 4
Author: Dhruv Hegde
Image credit: NASA/ESA/ESO/Wolfram Freudling et al. (STECF)
This paper analyzes and examines the scientific significance of Quasars – with a preeminent focus on Quasar J0313-1806 – through an astrophysical perspective, accounting for observations, calculations, and prior research. This paper will discuss the fundamental characteristics of a Quasar, Active Galactic Nuclei, Supermassive Black Holes, and Redshift; alongside this, the history of Quasar research and the emergence of radio astronomy will be discussed in detail for the purpose of contextualizing the method of measurement for Quasars. Quasars number the millions and hold the key to reconciling the concept of general relativity and gravitational lensing with Newtonian dynamics, possibly paving the way for a unified theory of quantum mechanics that would reveal the theoretical connection of every physical interaction in the universe. The discovery and manipulation of Quasar J0313-1806 has already brought to light greater understanding of high-pressure ion jets and a compounding theory of supermassive black hole formation; however, there is still much to be researched and revealed within the field of Quasars.
Formal introduction to Quasars
Quasars have been an interesting intergalactic entity ever since their initial observation. Within the astronomical community, quasars hold a distinct position as celestial brutes that possess the propensity to expel energy in great magnitude, with even the most enervated keeping a rate thousands of times that of the Milky Way galaxy. However, despite their prolific standing and puissant capabilities, they remain almost unknown to the general public. Nonetheless, research being done on Quasars may be an eminently valued commodity in the near future, for not only are they a predominant factor in the Black Hole Information Paradox, but they also give us an insight into energy conversion and concentrated matter.
Essentially, a quasar is a supermassive black hole that can be classified as an AGN (Active Galactic Nucleus). As many know, black holes are overly compressed volumes of matter that involve rapidly orbiting masses around them; Supermassive black holes, as their name suggests, are black holes with greater-than-typical masses. Think of it like this: a black hole is similar to a human, in that the more matter that it consumes, the larger it will grow, similar to how our body uses food for ATP and nutrients to help us grow taller and stronger; when a black hole is given inordinate amounts of matter to consume around it, it is like a hungry kid being given a feast full of delectable treats, and matter will naturally flow into the black hole and cause the accretion disk to expand. As the accretion disk grows, so does the amount of sheer matter it can reach, which causes an even greater reach for the black hole, allowing it to grow beyond expectation and become supermassive. Bearing resemblance to other AGNs such as Seyfert galaxies or Radio galaxies, Quasars often have a high luminosity factor, shining with an absolute magnitude that is generally between 1*10^3 to 1*10^5 times greater than that of our Milky Way galaxy altogether. One example of this is with Quasar 3C-273 – this was the first Quasar to be experimentally confirmed and calculated – which has a luminosity of 2.45*10^40 Watts, making it approximately 62.8 trillion times brighter than the sun in our solar system. While this may paint the picture of Quasars to be eminently large objects with massive proportions, Quasars are inordinately more dense than scattered spiral galaxies, for over a billion solar masses are generally forced into an accretion disk that is merely light-days across. So while Quasars, as supermassive black holes, are eminently gargantuan and hold their own in terms of cosmic proportion, they are mere specks compared to galaxies and are smaller than most expect due to their highly concentrated mass.
Active Galactic Nucleus
AGNs, as we briefly introduced during our discussion of Quasars, are highly concentrated regions of matter that simultaneously emit radiation across the whole electromagnetic spectrum and produce immense quantities of energy, which causes its immense luminosity factor. AGNs exist within active galaxies and are generally the only discoverable parts of supermassive black holes or Quasars; due to the central expulsion of electromagnetic radiation, they are the only persistent source of lumination in the universe, artificial telescopes are able to detect them from large distances. Within Quasars, or even blazars, the infalling material goes directly into the AGN and is expelled in the form of high-compression jets of radiation.
Grouped with Quasars, Seyfert 1 and Seyfert 2 galaxies are also AGNs that involve high-energy emissions and optical emissions that are similar to that of a Quasar. A Seyfert 1 galaxy can be seen to have both narrow and broad emission lines. They are on the Herculean types of active galaxies and contain millions of solar masses in the form of a collapsing supermassive black hole at the nucleus of the galaxy. Seyfert 2 can be distinguished through only having narrow emission bands on the slower end of the spectrum, but are able to grow slightly larger in size and mass than Seyfert 1. Both of these AGNs are comparable to Quasars in that they share a lot of commonalities or similarities with their absorption and release of matter.
In terms of ideal physical structure, Quasars, like other AGNs, have the structure of a simple black hole, but have an adjusted size and apparent magnitude. The nucleus of the Quasar is continuously active and is where the compressed matter, which is the same matter distorting the spacetime field, resides. Following this portion comes the infamous accretion disk, which is a visual disk full of gas and high-energy matter, such as ionized plasma, that is being drawn into the black hole and its incredible mass; interestingly, matter than enters the accretion disk, regardless of what the initial speed is, accelerates to almost the speed of light before reaching the nucleus.
Now, think back to the example I provided about the growth of black holes into their supermassive counterparts. Do you remember how I drew a comparison between a human consuming food and a black hole consuming matter? Now, adding further onto that example, there is a point in our lifespan, following or into our adolescence, that we begin to stop growing as much. For black holes, this limit on growth potential is called Eddington limit; this limit is a fixed quantity, based on the black hole’s characteristics, that dictates the maximum amount of matter that can be absorbed per unit time before any additional amount of matter will cause external pressure to overpower the active nucleus. Expectedly, this is not a common affair and many black holes do not cease to exist as a result of this limit, with over 95 percent of black holes remaining under the consumption of 50 billion solar masses, which is a common average for a black hole’s Eddington limit.
Importance of Quasar J0313-1806
Quasar J0313-1806 is one of the most, if not the most, important Quasar to have been experimentally confirmed. While it does not hold the record for being the most luminous quasar observed or even the first to have been discovered, it is the most distant quasar that has been experimentally derived so far. As I discuss later, at the time of discovery, J0313-1806 was calculated to be 13.3 billion light years away, making it the most red shifted Quasar to have been observed by humans. Given that redshift is a measure of the rate at which an object gets more distant relative to a given point, those with a greater redshift are far older than the ones with less; based on the observed spectral lines, astronomers can determine the approximate velocity and the age of the Quasar, with this quasar being formed 13.1 billion years ago, eminently close to the cataclysmic Big Bang event.
Additionally, whilst also being a record-breaker in its own right, J0313-1806 also gave scientists insight into the fluid-matter jet that emerges from the expulsion of radiation in Quasars. Following J0313-1806’s discovery, astronomers determined that the ionized jet streams were composed of highly-pressured, volatile gas that moved at 20% of the speed of light. Moreover, the sheer energy that is released from the Quasar also brings about active star fusion, which results in the development of independent solar masses. It is estimated that J0313-1806 produces over 200 solar masses a year, which, compared to the Milky Way’s relative value of 1 solar mass/year, is certainly a significant portion. The high fusion rate and the redshift value measured for J0313-1806 indicate that the host galaxy is moving farther away, at the approximate speed of universal expansion, and is ameliorating in size with each coming year.
However, scientists have been faced with a peculiar problem whilst studying this Quasar. Based on the measured size of the Quasar, and the active galaxy holding it, J0313-1806 could theoretically not become as big as it is without surpassing the Eddington limit if it began merely 13.1 billion years ago. For example, based on a study done by researchers at the University of Arizona, the supermassive black hole that is J0313-1806 would only have grown to be 10,000 times the size of the sun if it were to be mare 13.7 billion years ago and grew by the traditional method. Not only is it younger, but it is also 1.6 billion times as large as our sun, begging the question of how Quasar J0313-1806 got so large without being able to exceed the Eddington limit. The current explanation for this phenomenon came about with a different theory on the formation of a supermassive black hole, but the true explanation for this phenomenon is yet to be experimentally confirmed.
Image Credit: NASA, ESA and J. Olmsted (STScI)
Despite the presence of QSOs (Quasi-Stellar Objects) since the inception of the universe, with a peak population approximately 3 billion relative years into existence, they were only observed through radio wave emissions in 1962. Discovered through radio telescopes that were created by Cyril Hazard, MB Mackey, and Albert Simmons, Quasars were initially thought to be collapsing stars, for collapsing stars were one of the only known sources of radio waves, but this was ultimately revoked due to the fact that the observed Quasar, 3C-373, was far stronger than stars were observed to do during the time. Months later, this same group of Australian physicists were able to decipher that 3C-373 was not a singular source, but rather two interstellar objects that were independently producing large radio wave emissions in almost synchronized fashion.
Following its initial discovery, the Australian physicists aimed to exact its location further, so to receive visual and statistical evidence of its existence; they were eventually able to utilize the Hale Telescope, a 200-inch diameter telescope at Caltech with thickness of 23.5 inches and multiple lenses of focus, upon which they mounted a spectrograph to measure the frequency of the continuous radio wave signals that were being received. Soon, with this additional instrument under their control, the multiple sources of radio emission was found to be two jets of highly compressed gaseous material being released. The radio emissions were simply a byproduct of the massive energy release occurring at the site of 3C-373. From here, the concept of a Quasar was designed and several other tests were conducted to discover the intricate properties that comprise such an interstellar object. For example, the Balmer Spectrum, which consists of a series of various spectral line emissions from hydrogen atoms, was used to determine the redshift of this early Quasar, which was predicted to be closer to the ends of the observable universe.
Interestingly, Albert Einstein, the physicist best known for the General Theory of Relativity and the Photoelectric Effect, was involved in the experimental discovery of Quasars. On January 1st, 1979, experimental physicists were able to capture the first visual depictions of a Quasar. This Quasar, known most commonly as the Twin Quasar, was found as a result of observations for gravitational lensing, a concept that mentions that objects that occupy a mass bring curvature to the space-time plane, with more massive objects causing more severe distortions for light and matter. The Twin Quasar that was discovered that day was not physically composed of multiple Quasars, but involved the distortion and misdirection of light in a way that brought two Quasar images to appear despite its singular presence. Following this discovery, various other Quasars were experimentally detected through radio wave emissions and the Hubble Space Telescope, which emerged in 1990 and helped to spot a distant Quasar whilst simultaneously providing redshift speed and the relative luminance value. However, it was in 1991 where our subject came to focus; on August 20th, the Hale telescope once again provided the advancement of Quasar identification, for it revealed a Quasar approximately 12 billion light years away. This Quasar was none but the J0313-1806, which has the greatest redshift of any observed quasar and has been confirmed as the oldest supermassive black hole in our observable universe. It was calculated to be over 13.3 billion light years away from our solar system and it formed merely 670 million years following the Big Bang, making it one of the oldest possible quasars to even theoretically exist, let alone experimentally.
Since the inception of the 21st century, revolutionary data regarding Quasars have yet to emerge and there has not been statistically significant data indicating any predominant Quasar discoveries in the past decade. In this century, noteworthy discoveries related to the field of radio astronomy have mostly revolved around the 2001 identification of the largest structured mass in the known universe, which involves the connection of several adjacent Quasars and Seyfert galaxies, and the 2006 study done at the Chandra X-Ray observatory regarding the ignition and formation of Quasars. Despite new data being received from over 26 major telescope observatories, Quasars have become less relevant in the astronomic sphere and have become yet another cosmic actuality that remains to be researched and harnessed.
Quasars, as we have discussed, are obviously important for measuring universal expansion rates and how they are manipulated over time; as a result of their large redshifts and their preeminent position, Quasars near the edge of the observable universe allow scientists on earth to measure the relative size of the universe at a given time when the light was first signaled. Following this procedure, comparing the relative size of the universe then to our calculations now, the logarithmic rate of expansion can be found and we can be able to pinpoint the location of the Milky Way galaxy relative to other galaxies and even the oldest interstellar actualities to exist.
Moreover, given that Quasars lie on the basis of General Relativity, it is yet to be shown to operate similarly through classical or Newtonian dynamics. Being able to unify these theories in unison, with Quasars being the medium of connection, would draft the first iteration of a unified field theory for Quantum Mechanics; this “theory of everything” concept would unlock the doors towards the study of theoretical particle interaction and the answers to various astrophysical conundrums, with the Black Hole Information Paradox being just one of them. The world of Quasars holds a lot of promise and intrigue and it could become an enticing field of study in the near future.
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