Questions tagged [quasars]
31 questions
56
votes
2 answers
2002 research: speed of light slowing down?
Back in 2002 there was some research published hinting that $c$ may have been faster at some distant point. It was based on measurements of the fine-structure constant,
$$
\alpha = \frac1{4\pi\epsilon_0} \frac{e^2}{\hbar c} \approx \frac 1{137},
$$
…
Errol Hunt
- 1,146
23
votes
2 answers
How can Quasars emit anything if they're black holes?
We've heard it many times, nothing can escape the gravity of a black hole, even light once it's past the event horizon. If this is true, how can a black hole emit anything? Quasars are massive black holes that have consumed enormous amounts of…
Hunter
13
votes
2 answers
Do quasars exist today?
Are there likely to be any quasars right now, or are all the ones we're seeing old galaxies today, like the Milky Way?
MissingUTAH
- 131
10
votes
2 answers
Which way do black hole jets spin?
The centers of black holes and quasars often have jets coming out the two poles of an accretion disk, say north and south. Is it known if the two jets spin in the same direction or opposite directions to each other?
AnimatedPhysics
- 658
6
votes
1 answer
History of the Milky Way-Quasar
Was our Milky Way a Quasar many years ago? I heard that it is difficult to fuel quasars for many billions of years, after a quasar finishes accreting the surrounding gas and dust, it becomes an ordinary galaxy.
5
votes
1 answer
What is the difference between a quasar and an Active Galactic Nucleus (AGN)?
In answering another Phys.SE question about quasars - Why no new quasars? - an issue arose about which object is the nearest quasar. That got me puzzled. To what is the label "quasar" attached, as opposed to just an "Active Galactic Nucleus" (AGN)?…
ProfRob
- 141,325
4
votes
1 answer
Quasars to a galaxy
Do quasars collapse and make a galaxy or do they eventually spew out enough matter to make one? Because I heard they are the center of galaxies, and I wonder if they can collapse from their own gravity or from becoming unstable, and if so, what…
Kellan Heerdegen
- 103
4
votes
1 answer
What is Cosmic Downsizing?
I've had a quick look at a few lecture pdfs and papers as supplementals to my own given lecture notes, but I can't seem to get a proper explanation for what cosmic downsizing is.
The closest explanation I have is that it is the lower population/size…
Wrothschild
- 147
4
votes
1 answer
Why can't friction in an accretion disk radiate away enough of the angular momentum do create inward spiral?
As almost every source that I'd found explains, it was a challenge for scientists to understand the mechanism by which the total angular momentum in the accretion disc was conserved, while taking the latter (total conservation of angular momentum)…
Max
- 611
4
votes
2 answers
Could quasars produce elements heavier than oxygen?
I have read that supernovae are the main producers of elements heavier than oxygen. I just wonder whether quasars, which have been around a long time just like supernovae have, could have had a comparable material effect on the universe. With all…
Richard Peterson
- 140
4
votes
2 answers
How do we know that Quasars actually produce collimated jets?
How did astrophysicists know this? Of course it's very difficult to directly see the jets from Quasars, so I'm wondering how did they come to the conclusion that Quasars produce collimated jets or beams?
user43783
- 1,137
4
votes
1 answer
What is a quasar flux ratio anomaly?
In the context of strongly lensed, multiply-imaged quasar observations, I sometimes hear about "flux ratio anomalies". What are these? Why are they important?
Kyle Oman
- 18,883
- 9
- 68
- 125
3
votes
1 answer
How do we know that quasars are not white holes?
White holes are speculative in nature. Black holes are known to exist (supermassive black holes in galactic nuclei and stellar-mass black holes in binaries).
My question: if white holes are expected to be very luminous objects, how do we know…
Daddy Kropotkin
- 2,790
3
votes
2 answers
How does a quasar convert mass to energy?
I'm trying to understand where the energy for a quasar comes from and specifically if it comes from converting mass to energy.
I know that as matter falls into a black hole gravitational energy is converted to heat and other kinds of energy but that…
QuasarBoy99
- 31
2
votes
1 answer
What makes black holes pink? (Paul Francis' research)
So, a while back I have stumbled across some articles about "pink black holes" and just put it off as a scam, like many news. But not so long ago I found Paul Francis, an astrophysics researcher, and his very colourful vest was what actually…
