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25 votes

Why are all quasars so far away?

There are essentially two reasons. First, quasars are rare objects, so even though they are homogenously distributed on large scales, the average distance is large. Moreover, the brightest quasars ...
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16 votes

Why are all quasars so far away?

You have stumbled across a profound observation and almost grasped one of its most important consequences. There are two forms of the so-called cosmological principle. There is the more limited ...
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16 votes

How can gravitational lensing makes a quasar appear brighter?

The quasar gives out light in all directions. The light spreads out in space. Only a very small amount of that light would be pointed exactly in the direction of your telescope. But if a large galaxy ...
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13 votes
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What does "Effective radius of [CII] line is 1.4 kpc" mean?

Defining the radius As the surface brightness (SB) of extended objects does not reach zero at some well-defined radius, we need a measure to be able to compare various objects. Probably the most used ...
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12 votes
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Quasar mass and accretion rates

Tricky to say for sure, but I would imagine it comes about from measurements of the luminosity and inference of the black hole mass in such systems. The most extreme objects radiate at the Eddington ...
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11 votes
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Why are all quasars so far away?

The discussion of the Cosmological Principle above is very relevant, but it is possible that so is a (weak) application of the anthropic principle - in other words if we were in a region of extremely ...
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10 votes

How are neutrinos produced in blazar jets?

Neutrinos are typically produced in AGN jets through what we refer to as hadronic processes. Protons are accelerated to relativistic speeds and interact with nearby photons. Depending on the ...
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10 votes
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Why are quasars so far away that they couldn't be optically resolved in the 1950's?

Quasars have a very low density at the present epoch, but were much more common in the past. Their co-moving space density peaks at redshifts of 2-3. The evolving space density of bright quasars. ...
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9 votes
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Quasars and Gamma Ray Bursts

I think you may be mixing up "Energy" and "Power" a little here. Power is the rate of Energy output per time. If Power is the speed, then Energy is the distance travelled. Quasars look like stars, ...
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8 votes

Difference between quasar and Active Galactic Nuclei?

All quasars are AGN, but not all AGN are quasars. AGN is a terminology that comes later than quasars. Quasars is the term applied at the beginning, when the first objects of this type have been ...
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7 votes
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Difference between quasar and Active Galactic Nuclei?

A quasar is a type of AGN. Its main property is that it's galaxy axis points towards the earth and this way we receive its light and radio signals. That's why they are one of the most energetic AGN. ...
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7 votes

Quasar Redshifts

The optical emission lines of quasars do not come from sufficiently close the the central supermassive black hole to be appreciably gravitationally redshifted. If they did arise from gas near the "...
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7 votes

Why would the merger of spinning black holes within the accretion disk of a supermassive black hole cause them to "shoot straight up" out of the disk?

Let me see if I can try answering both parts of your question. The key is a combination of two things: 1) Most of the binary BHs in an accretion disk will have their binary orbits in the same plane as ...
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Is quasar 2M1310-1714 outside the observable universe?

The redshift of the quasar is 1.975, so it is nowhere near the edge of the observable universe. 17 billion light years is the comoving distance (i.e. where it is now), as you can confirm with this ...
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6 votes
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What is the scale of things you can see with gravitational lensing?

You are right that the stars seen on the sky are within the Milky Way. Only with a large telescope is it possible to resolve individual stars in other galaxies, and only for the nearest ones. I don't ...
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6 votes
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Can we extract power from quasars?

We could, but there isn't enough energy to make it worthwhile. These types of radiation are referred to as "highly energetic" because each individual particle (or very short burst) has comparatively ...
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6 votes
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light emission of quasars

The statement "They're only emitting infrared light" is wrong, or at least poorly phrased. The Ly$\alpha$ forest The Ly$\alpha$ forest (LAF) is caused by the spectrum of the quasar being redshifted ...
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6 votes

Could quasars be interior to the event horizon of a SMBH?

the Quasar Age or Quasar Epoch has ended. As pointed out by James K., the Quasar epoch has not ended. Today quasars are rarer then some Gyr ago, but they are still here. The closest one is about 600 ...
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6 votes
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What does "TON" in TON 618 stand for?

Tonantzitla Observatory. See https://en.wikipedia.org/wiki/TON_618 and https://en.wikipedia.org/wiki/Tonantzintla_Observatory
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5 votes

Is it possible that quasars are not powered by black holes but some other kind of compact, massive object?

The solution to your question is surprisingly simple, I think: A quasar that puts out energy around Eddington luminosity or higher, must accrete at a certain rate, corresponding to the energy output. ...
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5 votes

If quasars are powered by black holes, why are they so bright?

The light emitted isn't actually from the black hole itself but the swirling matter that surrounds it called the accretion disk. The light emitted from the accretion disk is far enough to escape from ...
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5 votes

How to find the distance between two quasars

Edit: I found you a very relevant paper! http://arxiv.org/pdf/astro-ph/0007341v1.pdf seems to be solving exactly your problems for sources with arbitrary angular separation $\alpha$. Equations (12) ...
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5 votes
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What is projected separation and how can I make sense of its unit (h^-1 kpc)?

It means the separation between the two objects if they were both at the same distance away. This separation is found by multiplying the angular separation (in radians) by the distance to the objects. ...
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5 votes
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How does science knows what is the early universe?

I assume you're referring to the recent press release about the quasar J043947.08+163415.7, observed recently using Hubble. The paper about the observations details how the authors measured the ...
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5 votes

How to interpret this spectrum of the "new DESI Quasar at z = 6.53"; what causes the big edge at about 9150 Angstroms?

The jump occurs at the redshifted wavelength of the Lyman-$\alpha$ line, so this is the Gunn-Peterson trough, which is caused by neutral hydrogen in the intergalactic medium suppressing any radiation ...
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5 votes

How to interpret this spectrum of the "new DESI Quasar at z = 6.53"; what causes the big edge at about 9150 Angstroms?

Thomas' answer is completely correct, I'd just like to elaborate a little on the reason for such a spectrum. Quasar spectra generally have broad emission lines, in particular Lyman $\alpha$ at a rest ...
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4 votes

Why are all quasars so far away?

in the early universe there was more diffuse matter in gaseous form available to the black holes. The galaxies were more foggy with diffuse matter and less void, so a BH travelling through a galaxy ...
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4 votes
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Mass distribution in the early universe

It is unfortunate that the usual poor journalism labels the growth of the black hole as "inexplicable" and then further down in the article refers to some possible explanations. The basic problem is ...
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4 votes

Gravitational lensing of quasars

Yes, there are many. One of the first, if not the first was the radio lensed quasar B1938+666, in which a near-IR Einstein ring was reported by King et al. (1998). The answer to your real question ...
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