Limits of the Universe

[petrushka.googol]

Quasars are said to define the limits of the observable Universe.

 

Such an aggregation of mass (quasars are super-massive black holes) at the periphery of the observable Universe may curve space time back upon itself and actually define not only the limits of the observable Universe but of the Universe itself.

 

How far is this true?

 

Please elicit your opinion.

 

Thanks in advance.

[Airbrush]

Our own galaxy would appear as a quasar viewed by anyone looking towards us from the "edge" of the universe. Does that make our galaxy the "edge" of the universe?

[imatfaal]

Our own galaxy would appear as a quasar viewed by anyone looking towards us from the "edge" of the universe. Does that make our galaxy the "edge" of the universe?

 

Are you sure about that? Not all galaxies would be seen as quasars from a distance - only those with a particularly voracious accreting super-massive blackhole at the centre. I don't know what the milky way was like 12-13 billion years ago - but I am not sure it was a quasar.

[EdEarl]

Quasars vary in distance from the Earth, see the following:

list of quasars

redshift

[Airbrush]

 

Are you sure about that? Not all galaxies would be seen as quasars from a distance - only those with a particularly voracious accreting super-massive blackhole at the centre. I don't know what the milky way was like 12-13 billion years ago - but I am not sure it was a quasar.

 

Was the Milky Way's supermassive black hole (SBH) ever a quasar? I do believe ALL supermassive black holes begin as quasars simply because that is what happens to gas and dust close to a SBH until all local stuff gets "eaten". After that, it goes dormant.

 

How could a SBH form and not be a quasar upon formation? Even if the quasar stage lasts only Millions of years, it had to be a quasar to begin with.

Edited October 22, 2013 by Airbrush

[BusaDave9]

Our own galaxy would appear as a quasar viewed by anyone looking towards us from the "edge" of the universe. Does that make our galaxy the "edge" of the universe?

No our galaxy is not a quasar.

 

 

Are you sure about that? Not all galaxies would be seen as quasars from a distance - only those with a particularly voracious accreting super-massive blackhole at the centre. I don't know what the milky way was like 12-13 billion years ago - but I am not sure it was a quasar.

Imatfaal is correct. Quasars are massive black holes at the center of some galaxies. They are the brightest objects in the universe. Actually they don't seem to exist anymore. They were much more common early on in our universe. Most quasars are so distant they are almost moving away from us at the speed of light (red shift from the expanding universe).

[Airbrush]

No our galaxy is not a quasar.

 

Imatfaal is correct. Quasars are massive black holes at the center of some galaxies. They are the brightest objects in the universe. Actually they don't seem to exist anymore. They were much more common early on in our universe. Most quasars are so distant they are almost moving away from us at the speed of light (red shift from the expanding universe).

Our galaxy is not a quasar NOW, but when our supermassive black hole (SBH) first formed it was a quasar. How can a SBH form without a quasar stage, no matter how long it lasted? I'm just using common sense, no wiki article to back me up.

 

The question is: do all supermassive black holes begin as quasars? I think the answer is yes. How could it be no?

[petrushka.googol]

The question is: do all supermassive black holes begin as quasars? I think the answer is yes. How could it be no?

 

From my elementary knowledge Quasars are quasi stellar radio sources - super massive black holes red shifted significantly (Doppler) indicating a pristine evolution.

My feel is that while all quasars are super massive black holes, the converse need not necessarily be true.

[BusaDave9]

My feel is that while all quasars are super massive black holes, the converse need not necessarily be true.

I agree. When a massive star becomes a black hole it will not become a quasar unless there is still a lot of matter nearby to fall into the hole and create the energy source for the quasar. A young galaxy could have that matter.

[Airbrush]

I agree. When a massive star becomes a black hole it will not become a quasar unless there is still a lot of matter nearby to fall into the hole and create the energy source for the quasar. A young galaxy could have that matter.

 

We are not discussing stellar black holes that form from a single massive star collapse. We are talking about supermassive black holes with masses of Millions or Billions of solar masses. They had to form very early in the universe, before any stars formed. Their formations would be extremely energetic events. Not all the matter can cram itself into the giant black hole, so most is blasted off as polar jets which lasted less than a Billion years. Those polar jets are quasars. Quasars are the result of the early stage of SBH formation.

My feel is that while all quasars are super massive black holes, the converse need not necessarily be true.

 

I never suggested all supermassive black holes ARE quasars, only that they FORMED as quasars.

 

".....The difficulty in forming a supermassive black hole resides in the need for enough matter to be in a small enough volume. This matter needs to have very little angular momentum in order for this to happen. Normally, the process of accretion involves transporting a large initial endowment of angular momentum outwards, and this appears to be the limiting factor in black hole growth. This is a major component of the theory of accretion disks. Gas accretion is the most efficient, and also the most conspicuous, way in which black holes grow. The majority of the mass growth of supermassive black holes is thought to occur through episodes of rapid gas accretion, which are observable as active galactic nuclei or quasars. Observations reveal that quasars were much more frequent when the Universe was younger, indicating that supermassive black holes formed and grew early. A major constraining factor for theories of supermassive black hole formation is the observation of distant luminous quasars, which indicate that supermassive black holes of billions of solar masses had already formed when the Universe was less than one billion years old. This suggests that supermassive black holes arose very early in the Universe, inside the first massive galaxies."

 

http://en.wikipedia.org/wiki/Active_galactic_nuclei

Edited October 24, 2013 by Airbrush

[BusaDave9]

Such an aggregation of mass (quasars are super-massive black holes) at the periphery of the observable Universe may curve space time back upon itself and actually define not only the limits of the observable Universe but of the Universe itself.

True, near a black hole spacetime is warped. This is true of any gravitational force but in the case of a black hole the space-time continuum is infinitely warped at the event horizon. For a spaceship to stay at the event horizon it would have to travel at the speed of light. Anything beyond the event horizon would have to travel faster than the speed of light. For that reason it can be said that anything beyond the event horizon is not within our universe. Some say a black hole may be a worm hole to another universe or another place and time in our universe. But all that is speculation. Once anything passes the event horizon it can't even send radio waves, light or any signal back past the event horizon.

 

 

 

Not all the matter can cram itself into the giant black hole, so most is blasted off as polar jets which lasted less than a Billion years.

How much "space" is there in a black hole?

It's a meaningless question because space and time don't have meaning beyond the event horizon. The dimensions of our universe are infinitely warped. There is no limit to how much matter can fit "inside" a black hole. If a massive star falls into a black hole nothing of the star exists anymore except the gravity. The black hole will have a stronger gravitational force. For that reason the event horizon will be slightly bigger.

[Airbrush]

There is no limit to how much matter can fit "inside" a black hole. If a massive star falls into a black hole nothing of the star exists anymore except the gravity. The black hole will have a stronger gravitational force. For that reason the event horizon will be slightly bigger.

 

Yes, there is no limit to how much matter can fit inside a supermassive black hole. But not all the matter of a star or cloud of gas/dust, that falls into it, will ENTER the supermassive black hole. A good amount of it is blasted away in polar jets. Those jets are called quasars.