Whichis the heaviest object in the universe ?

[atlantisworp]

If all planets and stars circle around the heaviest object, their must, somewhere, be the one, as center of the universe, where is it dear fellows Americans?

 

[MeteorWayne]

Sorry, but since the objects in the Universe aren't circling anything, there is no such object. There is also no center of the Universe.

Supermassive black holes at the center of Galaxies are probably the heaviest in a small space, but then again, a Galaxy could be considered and object as well. So could a cluster of galaxies.

 

[atlantisworp]

Sorry, but since the objects in the Universe aren't circling anything, there is no such object. There is also no center of the Universe.

Supermassive black holes at the center of Galaxies are probably the heaviest in a small space, but then again, a Galaxy could be considered and object as well. So could a cluster of galaxies.

‘objects in the Universe aren't circling anything‘
‘Orbiting’ is that a bet word for you or is it also wrong?
Black holes are the centers of each galaxy, that means that those are heaviest of each and every galaxy right?
Group of galaxies form a cluster, what do they do. Do they orbit also around something?

,

 

[MeteorWayne]

I assumed you meant orbiting when you said circling.

Not every galaxy has a black hole at the center as far as we know, but it appears that most do.

Groups of galaxies orbit around the center of mass of the galaxy, just as stars in a galaxy orbit around the center of mass of the galaxy, and Sun and the planets in the solar system orbit around the center of mass of the solar system, and the moon and earth orbit around the center of mass of the earth-moon system.

Sometimes the center of mass of the solar system is outside the surface of the sun, and we can actually see the sun orbit around that point.

The center of mass of a system is called the barycenter.

 

[drwayne]

I *think* where the question is leading is something like this (or not)

If one had accurate enough state data on the elements of the visible universe, then it is might be possible
with this data to ascertain a "gravitational center" of the mass distribution that is the visible universe,
and possibly characterize the mass environment there. (A black hole, or simply a large super Walmart)

Wayne

 

[MeteorWayne]

I think that's a generous interpretation of the intent . However, in fact, since most of the Universe is not populated by stars or galaxies, it would be highly unlikely that there would be an object at the center of mass of the Universe, other than a few stray atoms and photons, and possible a Resteraunt. Just as there is no object at the center of mass of the Pluto-Charon system other than a few stray atoms and photons.

 

[drwayne]

I have been wrong before - in the last few minutes.

Wayne

 

[Mee_n_Mac]

The OP might want to look at this page (previously posted here) ...

http://www.atlasoftheuniverse.com/

While I know English isn't his first language and there are translation difficulties, I sense there was a concept on the OPs part that .... because small scale structures in the universe often have a mass at their center, that this was a "law" to be followed at the larger scale of the universe ... with a correspondingly more massive body at it's center. As already stated this doesn't appear to be the case. Nor would it be the expected case.

FWIW : I'll opine that at the center of our observable universe it's more likely there's a Costco or BJs than a Super Walmart. Either that or a very chic jewelry emporium. I'm not sure which.

 

[atlantisworp]

I assume by these explanations, that black holes go no where else or move in orbit of anything at all.
Right?

 

[yevaud]

Well, yes and no. True, once a Singularity has formed, it generally is at the epicenter of the explosion caused by it's parent star's collapse; and yes, Singularities do orbit other bodies. But there's nothing to prevent the circumstances that would allow one to go "rogue," so to speak.

After all, going past the obvious, it's just another stellar object with mass.

 

[MeteorWayne]

I assume by these explanations, that black holes go no where else or move in orbit of anything at all.
Right?

Really, a black hole will continue moving in the same direction it was moving before it became a black hole. It's the same amount of mass, just in a smaller package, so will respond gravitationally in exactly the same way. Of course any force generated in the forming explosion could have an effect, but that's jusy basic gravity.

You really need to spend some time understanding how gravity works, in my opinion. Black holes are not magic, they are just a certain amount of mass compressed in a small space.

 

[Mee_n_Mac]

I assume by these explanations, that black holes go no where else or move in orbit of anything at all.
Right?

I don't understand what exactly you mean by "go no where else". Black holes (BHs) at the center of galaxies go wherever the galaxy as a whole goes. There's some research that suggest it's possible for a BH to escape it's own galaxy during the merger of 2 or more BHs.

http://www.iop.org/EJ/abstract/0004-637X/678/2/780

A solar system, whose sun has collapsed into a BH, continues it's prior path. In our galaxy that would generally mean an orbit around the galaxtic center though ejection from the galaxy is not impossible.

http://www.physorg.com/news2985.html

So the rule is the BH behave no differently than a star of the same mass. It goes whereever gravity tells it to go.

 

[DrRocket]

Re: Which is the heaviest object in the universe ?

If all planets and stars circle around the heaviest object, their must, somewhere, be the one, as center of the universe, where is it dear fellows Americans?

There seems to be a misconception that has propagated in this thread.

It is NOT true that planets and stars circle around the heaviest object. It is not clear that they orbit anything. It is not true that there are necessarily any stable orbits at all. It is not even known if our solar system is stable in the long term (don't worry simulations show that things will be OK for several lifetimes).

What is true is that if there are two isolated bodies, that one can solve the equations of motion governed by gravity. You can solve those equations for the motion of one body with respect to the other, or for the two bodies with respect to their center of mass (the usual equations in text books are not in the center of mass coordinates but describe the motion of one body relative to the center of the other body). The equations are quite similar in either case and the result is an orbit that is a conic section. Commonly that conic section is an ellipse.

In the case of three or more bodies the equations of motion don't provide a solution and the center-of-mass coordinate system does not provide any help. There are no closed-form solutions and the orbital paths may or may not even be stable. You may not have any sensible orbit at all, let alone one around a center-of-mass. Such orbits are basically a complete mystery.

References: Orbital Mechanics by Prussing and Conway
An Introduction to the Mathematics and Methods of Astrodynamics by Battin
http://en.wikipedia.org/wiki/N-body_problem

The universe cannot, no matter how you shake and bake the equations, or slice and dice them, be considered as anything other than a many-body system. Two-body models just don't apply. There is no clear orbital structure and no clear center for orbits that probably are not well defined anyway.

 

[atlantisworp]

‘It goes whereever gravity tells it to go‘
But gravity depends on mass amount, so probably the whole universe orbits around a huge mass or monolite.
Right?
If black holes move as stars do, do they orbit to something heavier them themselves, or is this the limit to human understanding?
Is there any object`(star) in the universe not moving?
I ask this all, because motion and stillness may be the clue to something.

 

[kg]

Re: Which is the heaviest object in the universe ?

[The universe cannot, no matter how you shake and bake the equations, or slice and dice them, be considered as anything other than a many-body system. Two-body models just don't apply. There is no clear orbital structure and no clear center for orbits that probably are not well defined anyway.

How would you describe many-body systems? Say a globular clustar of stars, they are gravitationaly bound together but none of the stars is orbiting anything?

 

[MeteorWayne]

‘It goes whereever gravity tells it to go‘
But gravity depends on mass amount, so probably the whole universe orbits around a huge mass or monolite.
Right?
If black holes move as stars do, do they orbit to something heavier them themselves, or is this the limit to human understanding?
Is there any object`(star) in the universe not moving?
I ask this all, because motion and stillness may be the clue to something.

For the detailed and accurate answer please read Dr Rocket's reply just above your question.

For a rough approximation, please reread my answer above that end with the word barycenter.

We have both answered your question, to different levels of complexity.

We can answer them a hundred times, but it will come out the same. You question has been answered.

As to your third point ("I ask this all, because motion and stillness may be the clue to something"), since there is no center to the Universe, and no reference frame to compare motion to, there is no way to answer your question. It is by definition, an invalid question. Nothing is still, and there is nothing to compare motion to.

Wayne

 

[drwayne]

My wife can tell you what the most dense object in the universe is.

Wayne

 

[MeteorWayne]

Re: Which is the heaviest object in the universe ?

[The universe cannot, no matter how you shake and bake the equations, or slice and dice them, be considered as anything other than a many-body system. Two-body models just don't apply. There is no clear orbital structure and no clear center for orbits that probably are not well defined anyway.

How would you describe many-body systems? Say a globular clustar of stars, they are gravitationaly bound together but none of the stars is orbiting anything?

That is correct. As I said to atlantisworp, Dr Rocket's answer is technically correct. Hope he won't mind if I paraphrase....Once there are 3 bodies in a system, the solution is chaotic. There is no way to predict how the motion of the objects will evolve with infinite precision forever.

And my answer is good enough for shorter periods, objects orbit the center of mass of their gravitational influences. That's good for a while, but eventually Dr Rockets statement that they are unpredictible over long periods becomes correct.

So over short periods, stars in a cluster roughly orbit the center of mass of the whole cluster. There is no need for there to be an object at that point. But wait long enough, and every object in the cluster can wind up anywhere, in any short term orbit, or be ejected from the system entirely. Same as the planets in the solar system. Over short periods (billions of years) they come very close to orbiting the center of mass of the solar system (which is not at the center of the sun, and sometimes isn't even within the sun) but over long enough periods, the planets can wind up anywhere in relation to the sun, even be ejected from the solar system entirely.

 

[MeteorWayne]

My wife can tell you what the most dense object in the universe is.

Wayne

Wayne,

What a "concidence"! Wayne is the exact same answer my wife would give

Wayne

 

[DrRocket]

Re: Which is the heaviest object in the universe ?

[The universe cannot, no matter how you shake and bake the equations, or slice and dice them, be considered as anything other than a many-body system. Two-body models just don't apply. There is no clear orbital structure and no clear center for orbits that probably are not well defined anyway.

How would you describe many-body systems? Say a globular clustar of stars, they are gravitationaly bound together but none of the stars is orbiting anything?

The N-body in dynamics describes any dynamical system consisting of 3 or more bodies. Generally they interact gravitationally, which is the case of interest here.

It is not to hard to describe them,in the sense of writing down a set of differential equations that does the job. But there are no closed-form solutions when the number of bodies is 3 or more.

It may be one that one body is so large that ignoring the others permits a solution as a series of two-body problems -- that is what is done to calculate the orbits of satellites around the earth and I think for most calculations of planetary orbits. But when extreme accuracy is needed the solution is done numerically with a dynamical code that simulates the many-body dynamics.

You would have to ask an astronomer how they calculate galactic rotations and star trajectories in detail, but I suspect that they use some sort of two-body approximation, treating the tenter of the galaxy as one body, or treating the galaxy as constructed of uniform rings which act like a single large body for purposes of the calculation.

But when you start talking about structures like groups of local clusters, I doubt that such an approximation would be accurate. But again you would really need to talk to a specialist to see how they do such problems in practice.

The point is that the many-body problem is fundamentally difficult and can exhibit complex behavior, including paths with no "center". Some call such systems "chaotic" but I have a dislike for use of that term without a rigorous definition, and the use of the term in this context is very loose.

 

[DrRocket]

If all planets and stars circle around the heaviest object, their must, somewhere, be the one, as center of the universe, where is it dear fellows Americans?

There is one answer.

Cosmologists typically assume that the universe is, on the largest scales homogeneous and isotropic. It is that assumption, and consequences of it that permit a notion of global "time" and global "space" to be developed in a model based on general relativity.

With that approximation the center is the location of the original Big Bang. And the answer to that is that it is right here in my office. Right at the point of the "I" on my keyboard. No kidding that is correct. That is the point.

Of course every other point in the entire universe is also the point of origin. Everywhere is the center.

Refer to the balloon analogy for further enlightenment.

 

[SpeedFreek]

Here are some simulations of gravity, to illustrate what DrRocket means when he talks of chaotic systems:

3D Gravity Simulation

Physics - Particle Gravity Simulation - part 1

Gravity Sim 3.0

 

[DrRocket]

Here are some simulations of gravity, to illustrate what DrRocket means when he talks of chaotic systems

Thanks for the simulations speedy, but come on, remember that I said that I dislike the term chaotic systems when it is not used precisely and it almost never is used precisely. :shock:

For an example of imprecise usage, look almost anywhere the term comes up.

For an example of precise usage look in Bob Devaney's book An Introduction to Chaotic Dynamical Systems. The subject of this book is topological dynamics and Bob defines chaos precisely and rigorously in that context.

Most of the people who use the term use it very very loosely for "highly dependent on initial or boundary conditions", don't quantify the term and basically don't know what they are talking about -- and that includes some people with credentials whom you would think were authoritative.

 

[SpeedFreek]

I wasn't using it precisely either, of course. To me, in the context of this thread, it means that smaller things don't travel in circles around larger things, or sit still for very long!

I don't like the term chaotic either, especially when applied to the dynamics of the universe, as it implies a lack of order. The universe doesn't lack order, it just seems to have a very complicated kind of order (in the context of gravity, at least)!

 

[DrRocket]

I wasn't using it precisely either, of course. To me, in the context of this thread, it means that smaller things don't travel in circles around larger things, or sit still for very long!

I don't like the term chaotic either, especially when applied to the dynamics of the universe, as it implies a lack of order. The universe doesn't lack order, it just seems to have a very complicated kind of order (in the context of gravity, at least)!

Actually it is kind of interesting. The physics that governs the dynamics of the universe is stated rather simply and elegantly. The Einstein field quations are just kT=R where k is a constant, T is the stress-energy tensor and R is the curvature tensor. But that simple equation admits many intricate solutions of great beauty.

Similarly Newton's theory of dynamics is summed up with F =dp/dt but the solutions can also be intricate and beautiful.

The term "chaos" is often used as a substitute for "I don't know and I won't admit it, and if I use big words maybe no one will notice." In the case of clear and rigorous usage (see the book by Devaney) that is not true, but it is unfortunately the exception.