Quasars (pronounced QUAY-sars) are THE brightest known objects in the visible universe. They are so bright that they outshine the entire galaxy they sit in. They are also THE MOST distant objects ever on record. So, what are quasars? Where are they found? How do they become so bright? What are they made of? How far are they from us? Probably these questions have already bombarded your brain. So let us find the answers to all these questions and learn 25 interesting Quasar facts. Are you ready?
Did you know that the most distant quasar discovered is nearly 29 billion light years away from us?
Interesting Quasar Facts: 1-10
1. ‘Quasars’ is actually a short name for Quasi-Stellar Radio Sources. They actually belong to a family of objects which are together known as the active galactic nuclei (AGN). Of all the objects in AGN, the quasars are the most distant and most energetic objects.
2. Quasars are extremely bright or luminous. They are 100 times more luminous than our entire Milky Way. To put it in simpler terms, the total light emitted by 100 galaxies the size of our Milky Way is less bright than the light that is emitted by a quasar. Our Milky Way consists of nearly 200-400 billion stars!
3. According to scientists, a quasar is a compact region found at the central part of a massive galaxy and that this central region is actually surrounding the supermassive black hole that sits at the very center of the galaxy. A supermassive black hole has a mass equivalent to a billion solar masses (total mass of 1 billion suns).
4. Exactly how a quasar is formed is still a matter of debate and extensive research but the best guess that the scientists give is that the supermassive black hole starts consuming mass from the accretion disc, which heats up the matter (gasses and other material) falling into the black hole. The temperature can rise up to millions of degrees and the matter starts emitting light, x-rays, radio waves and other forms of radiation.
5. An accretion disc is a circular disc like structure usually made of gasses and the matter spins around the black hole at a very high speed. As matter starts falling into the black hole from the accretion disc, the friction between matters gradually heats up the matter, leading to energy emission.
6. The spinning disc of gas and matter form a magnetic field anchored to disc. The vertical magnetic field gets twisted at the top because of the fast spin of the accretion disc.
7. The energy or radiation of charged particles love magnetic fields and prefer to get attached to the magnetic field lines. So, as the disc rotates, these charged particles are shot upward and because of the twisted magnetic field lines, the charged particles form a tight column.
8. These columns are known as the astrophysical jets or cosmic jets or quasar jets.
9. These quasar jets shoot out to long distances but they don’t really originate from the center of the black hole but are rather emitted from spinning disc of gas and matter that gradually falls down into the black hole.
10. The charged particles inside the jets travel at nearly the speed of light, making them visible from a very long distance.
Interesting Quasar Facts: 11-20
11. The quasar jets that shoot out far into the space give rise to a phenomenon known as DRAGN or Double Radio Source Active Galactic Nucleus. This happens because the jets that shoot out of the quasar slam into intergalactic medium that exists between two galaxies.
12. This collision of the jets with intergalactic medium gives rise to massive hotspots which are known as DRAGN.
13. A DRAGN can extend to a distance of 1.5 million light years or more from one end to another end. That’s way larger than the galaxy where the quasar originated and gave birth to quasar jets which eventually produced the DRAGN.
14. Quasars show high redshift. A redshift is defined as an object’s light spectrum (when light is broken down into individual wave lengths, the range of wavelengths is known as spectrum) shifting towards the red end of visible light range. This simply means that an object is moving away from the point from where it is being viewed. Thus, quasars are actually shifting away from earth.
15. Quasars are drifting away from us at the speed of at least 93,200 miles per second (which is half the speed of light). Some quasars move at 93% of the speed of light.
16. Combining the redshift of the quasars with Hubble’s Law, scientists have figured out that quasars are THE MOST distant objects visible to us in time and space. The closest known quasar is 730 million light years away from us and is known as IC 2497. The farthest known quasar is the one that was discovered in June 2011 and named as ULAS J1120+0641. It is calculated to be at a distance of 29 billion light years from earth. Interestingly, this distance is a comoving distance and not a proper distance. So in terms of proper distance, the ULAS J1120+0641 is probably even farther than 29 billion light years.
A comoving distance is a distance between two objects at any given point in time assuming that the objects are not drifting away from each other because of the expansion of the universe. A proper distance, on the other hand, is a distance between the two objects at any given point in time assuming that the objects are drifting away from each other because of the expansion of the universe.
17. Because of the staggering distance of the quasars from earth, they are clearly THE MOST distant objects known to us. Why? Simple! The light of quasar that we see today had to cover a distance of millions or billions of light years. So, taking the case of ULAS J1120+0641, the light of that particular quasar traveled a distance of 29 billion light years!
1 light year = 9.4607 x 1015 meters ≈ 9.461 trillion kilometres = 9,461,000,000,000 kilometers.
Therefore, 29 billion light years = 9,461,000,000,000 x 29,000,000,000 kilometers = 274,369,000,000,000,000,000,000 kilometers = 274,369 quintillion kilometers
18. Quasars are the oldest known objects in the universe, they give an insight into the early years of the formation of our universe.
19. Quasars eventually die. This happens when the supermassive black hole consumes all the matter of the accretion disc and there is nothing left for it to feed on.
20. Perhaps our Milky Way once hosted a quasar but now it is dead. If the central supermassive black hole that sits at the very center of our galaxy comes to life once again, our Milky Way can once again host a quasar. This is not going to happen anytime soon. The only possibility of this happening is when Andromeda Galaxy (the nearest neighbor to our Milky Way) collides with our Galaxy some 3-5 billion years from now.
Did you know that Andromeda Galaxy is on a collision course with Milky Way?
Interesting Quasar Facts: 21-25
21. In general, a quasar with a black hole of 1 to 10 million solar masses will consume 1 solar mass a year. According to NASA, only so much matter per unit of time is present for a black hole that it is capable of consuming. So, for a 1-10 million solar mass black hole, only 1 to 10 million solar mass of matter will be available for consumption and hence, the life of a quasar with a 1-10 million solar mass black hole will be 1 to 10 million years. Thus, a quasar can have a life span of a few million years to a few billion years depending on the size of the supermassive black hole. Today’s largest known quasars burn mass every year that is equivalent to the mass of 1000 suns! Putting that in terms of earth, these largest quasars eat up mass equivalent to 600 earths every single day! This simply means that these super massive black holes that consume 1000 solar masses a year are 1000 times larger than the supermassive black holes of the size 1-10 million solar masses!
22. Most of the galaxies that we know today once hosted quasars during their early life. Gradually as the mass falling into their central supermassive black holes got depleted, their energy output reduced over time and eventually the quasars died, leaving behind the ordinary galaxies.
23. The first quasar that was discovered was in 1950 and was named as 3C 273. As of date, nearly 200,000 quasars have been discovered.
24. Quasars are called quasars because they are detected using radio telescopes. With a normal optical telescope, a quasar will look like a normal bright star. The difference between a quasar and a star is difficult to identify even with Hubble Space Telescope. A normal star will perhaps be a 100 light years away but a quasar will be millions or billions of light years away.
25. Scientists say that quasars, blazars and Seyferts are actually same and they look different simply because they are viewed from different angles. According to them, when the cosmic jet points directly towards us, we name them as blazars or blazar galaxies. When we look at them from side with a doughnut shaped ring of gas, dust and cloud in our direct line of sight, we do not see the bright core and the jets are pointed away from us, making them look less bright. These are known as the Seyferts or radio galaxies. In case of quasars, we are able to look towards the center of the galaxy with the cosmic jets angled in the general direction of earth but not in our direct line of sight.