Mysterious gas cloud that was supposed to enter Milky Way centralblack hole turned out to be a couple of merging stars instead!

On 18/11/2014 6:25 AM, sean wrote:
This is what I was disputing. How do you know the center of the milky
way is 4 million solar masses? (I assume you are referring to sagitarius A*)
My understanding is that this is only an assumption based on rotation
speeds of the observable stars like S2 etc. Maybe the understanding of
what g forces are at work in galaxy cores are incorrect. For instance we
know from rotation curves that the assumption that most of the mass of the
disc is in the core ,assuming estimates based on illumination,... is incorrect.

We know it's 4 million solar masses because we are using a highly
successful law of gravitation known as Kepler's Laws. These laws
predated Newton's Laws, and in fact were one of the influences behind
Newton's Laws. This law has been successfully used to figure out masses
of orbiting bodies for over 300 years. It's extremely precise, once we
know precise distances and speeds. The more precisely we know speeds and
distances between objects, the more precisely we'll know their masses.

Obviously the mass of the galaxy is spread much more evenly across the disc
then generally assumed. Maybe assumptions about rotation speeds in the core
are also incorrect. I don't see why one couldn't have the observed
rotational speeds near the center of the core without having to factor
in a Black Hole. We have no other precedence for core behaviour so
its odd we have to assume they behave like the solar system where most of the mass *is* at the center. And one of the points I made in previous posts was
that there are galaxy centers that astrophysists agree don't have black
holes (Yousof K cited one) , yet they are essentially disc galaxies with
cores. And as we cant see the rotational speeds of those cores one cant rule
out the possibility that these non BH galaxies also have stars rotating
at faster speeds at the center. Without a central black hole.

If you read about the Triangulum galaxy, which is thought to have either
no blackhole or a very small one, it's not because it didn't ever have
one, but it's possible that its blackhole was ejected after an
interaction with the Andromeda galaxy.

Yousuf Khan

Steve Willner wrote...
http://adsabs.harvard.edu/abs/2014MNRAS.443..791E http://adsabs.harvard.edu/abs/2014MNRAS.443....2E http://adsabs.harvard.edu/abs/2013PASJ...65..118S http://adsabs.harvard.edu/abs/2013AJ....146..121H

there are probably hundreds more in the literature.
I doubt there's even a single rotation-curve paper that
treats galaxy mass as a central point.

Those look like interesting papers thanks, and Ive eyeballed the
abstracts and will try to spend more time reading them in detail.

I can well understand that they *think* that they arent treating galaxy
mass as a central point. But the formulae they use definitely do...ie..
v=sqrt(GM/R). And thats why theyve screwed up with the assumption
fast orbital speeds means massive central black hole. In the same way
theyve screwed up by using the same formula to calculate erroneous
predictions that dont match observed rotation curves for discs....
they used the wrong formulae.
But you have avoided answering my question, so Ill try again..
Where in that formula or any other similar used, is the
part that specifies the mass is distributed across the disc?
I can answer for you if you want and its ...nowhere in that formula.
Bill suggests that even Newton admitted that its a point source as
Im arguing. But that it was 'effectively the same' as if one were
calculating for all the mass in the orbital radius. Maybe that
worked in the 17th century for the solar system. But not now
for core distribution . Newton probably didnt even know such
structures existed. Anyways as now and in his time the n- body
problem was considered impossible to calculate. And a core
distribution is about as complex an n body as we'll ever see.
So until someone does the impossible and calculates an n body
solution for a core then its unscientific to rule out a scenario
where a core with mass distribution across the core can give
very fast rotation curves at the center without a central black
hole. And its even more unscientific to try and calculate for one
using the wrong formula.

On 11/21/14 12:29, sean wrote:
Steve Willner wrote...
http://adsabs.harvard.edu/abs/2014MNRAS.443..791E http://adsabs.harvard.edu/abs/2014MNRAS.443....2E http://adsabs.harvard.edu/abs/2013PASJ...65..118S http://adsabs.harvard.edu/abs/2013AJ....146..121H

there are probably hundreds more in the literature.
I doubt there's even a single rotation-curve paper that
treats galaxy mass as a central point.

Those look like interesting papers thanks, and Ive eyeballed the
abstracts and will try to spend more time reading them in detail.

I can well understand that they *think* that they arent treating galaxy
mass as a central point. But the formulae they use definitely do...ie..
v=sqrt(GM/R). And thats why theyve screwed up with the assumption
fast orbital speeds means massive central black hole. In the same way
theyve screwed up by using the same formula to calculate erroneous
predictions that dont match observed rotation curves for discs....
they used the wrong formulae.
But you have avoided answering my question, so Ill try again..
Where in that formula or any other similar used, is the
part that specifies the mass is distributed across the disc?
I can answer for you if you want and its ...nowhere in that formula.
Bill suggests that even Newton admitted that its a point source as
Im arguing. But that it was 'effectively the same' as if one were
calculating for all the mass in the orbital radius. Maybe that
worked in the 17th century for the solar system. But not now
for core distribution . Newton probably didnt even know such
structures existed. Anyways as now and in his time the n- body
problem was considered impossible to calculate. And a core
distribution is about as complex an n body as we'll ever see.
So until someone does the impossible and calculates an n body
solution for a core then its unscientific to rule out a scenario
where a core with mass distribution across the core can give
very fast rotation curves at the center without a central black
hole. And its even more unscientific to try and calculate for one
using the wrong formula.

v = sqrt(GM/R) is the right formula, if M is the mass interior to the
orbit and the mass is spherically symmetric.

Newton did not "admit that it's a point source." Newton proved
mathematically that the gravitational force from a sphere is the same as
that of a point source of the same mass.

As for the n-body problem, although it does not admit a closed-form
analytic solution, it's very much amenable to numerical integration.
That's "calculating" it quite well. But that has little relevance for
the case at hand. The central mass is about a million times more than
the mass of any of the stars orbiting it, so each star basically follows
its own two-body orbit, and the star-star perturbations aren't
measurable with current observations.

Observed rotation curves for disks do indeed differ from what one would
compute under the assumption that all the mass in the galaxy is
luminous. That's a well known problem, and the only plausible
resolution is that there is a lot of mass that is *not* luminous. (What
that might be is a subject of active research and off topic for this
thread.)

What *is* unscientific is trying to force data into one's theory.
Science operates the other way: finding theories that agree with and
explain the data.

I have said enough in this thread.

-- Bill

On Friday, 21 November 2014 22:01:03 UTC, Bill Owen wrote:
On 11/21/14 12:29, sean wrote:
Steve Willner wrote...
http://adsabs.harvard.edu/abs/2014MNRAS.443..791E http://adsabs.harvard.edu/abs/2014MNRAS.443....2E http://adsabs.harvard.edu/abs/2013PASJ...65..118S http://adsabs.harvard.edu/abs/2013AJ....146..121H

there are probably hundreds more in the literature.
I doubt there's even a single rotation-curve paper that
treats galaxy mass as a central point.

Those look like interesting papers thanks, and Ive eyeballed the
abstracts and will try to spend more time reading them in detail.

I can well understand that they *think* that they arent treating galaxy
mass as a central point. But the formulae they use definitely do...ie..
v=sqrt(GM/R). And thats why theyve screwed up with the assumption
fast orbital speeds means massive central black hole. In the same way
theyve screwed up by using the same formula to calculate erroneous
predictions that dont match observed rotation curves for discs....
they used the wrong formulae.
But you have avoided answering my question, so Ill try again..
Where in that formula or any other similar used, is the
part that specifies the mass is distributed across the disc?
I can answer for you if you want and its ...nowhere in that formula.
Bill suggests that even Newton admitted that its a point source as
Im arguing. But that it was 'effectively the same' as if one were
calculating for all the mass in the orbital radius. Maybe that
worked in the 17th century for the solar system. But not now
for core distribution . Newton probably didnt even know such
structures existed. Anyways as now and in his time the n- body
problem was considered impossible to calculate. And a core
distribution is about as complex an n body as we'll ever see.
So until someone does the impossible and calculates an n body
solution for a core then its unscientific to rule out a scenario
where a core with mass distribution across the core can give
very fast rotation curves at the center without a central black
hole. And its even more unscientific to try and calculate for one
using the wrong formula.

v = sqrt(GM/R) is the right formula, if M is the mass interior to the
orbit and the mass is spherically symmetric.

No it isn't. It calculates gravity as if all the mass is at the center
of rotation. If you disagree show me the part of the equation that
calculates for all the objects and there positions in the volume.
Ive asked for this so many times on this thread and so far no one has
been able to show me . Because they cant.
Its an erroneous assumption that any mass outside the orbit doesn't
affect the orbiting star whose v is being calculated. And its an
erroneous assumption that the gravitational effect of all the mass
being spread around the volume defined by the orbit is the
same as the gravitational effect if all the mass were concentrated
at the center. A good example of this is they preccession of mercury`s
orbit. How did Urbain le Verrier account mathematically for this
anomaly? By adding a small extra mass orbiting inside mercury`s orbit.
But not included at the center.
Im not familiar with his calculations but he shows that the distribution
of mass is very important to orbital paths and speeds. In that if one
added the extra mass to the center, in the sun, one would not get
the same dramatic effect. In other words you can only correctly
calculate for orbital speeds and paths with an n body calculation.
Below you say its easy? Why hasn't it been done? I have read that with
n2 the higher n gets they more `chaos` enters the results. With the
amount of stars in the core, Im sure no one has ever tried.
Newton did not "admit that it's a point source." Newton proved
mathematically that the gravitational force from a sphere is the same as
that of a point source of the same mass.

That's because he calculated for a point source and because with the solar
system its virtually all in the sun anyways. He got so close that it
was acceptable. But he didn't get it exactly! Hence the observed
precession of planets. If he calculated for a mass distribution across the
radius of the volume of the sun with an n body calculation
Im sure the results would agree with the observed preccessions and
we wouldn't need GR. And Urban le Verrier seems to have concurred on this.

As for the n-body problem, although it does not admit a closed-form
analytic solution, it's very much amenable to numerical integration.
That's "calculating" it quite well. But that has little relevance for
the case at hand. The central mass is about a million times more than
the mass of any of the stars orbiting it, so each star basically follows
its own two-body orbit, and the star-star perturbations aren't
measurable with current observations.

Observed rotation curves for disks do indeed differ from what one would
compute under the assumption that all the mass in the galaxy is
luminous. That's a well known problem, and the only plausible
resolution is that there is a lot of mass that is *not* luminous. (What
that might be is a subject of active research and off topic for this
thread.)

The only plausible solution is that the luminosity calculations
are incorrect. And should they be too. If we cant see anywhere near
al the stars in any disc or core, how can we know how much we don't
see? Its bad science to give a less rigorous analysis based on luminosity
the same weight as the very accurate analysis one gets from observed
velocity curves. The reason why theorists have gone for this dubious
approach is that they cant admit that v=sqrt(GM/R) isn't appropriate
to calculate what should be n body calculations
What *is* unscientific is trying to force data into one's theory.
Science operates the other way: finding theories that agree with and
explain the data.
What you suggest, couldn't be scientific by this rule. You have a
theory that there are black holes at galaxy centers. To prove it
you erroneously force the data to fit the theory by making incorrect
calculations. Calculations that ignore the visible mass distribution
seen in cores.

In article ,
sean writes:
A good example of this is they preccession of mercury`s
orbit. How did Urbain le Verrier account mathematically for this
anomaly? By adding a small extra mass orbiting inside mercury`s orbit.

_Small_ extra mass so as not to change the period or shape of the
orbit, only the precession of the nodes. Non-spherical mass
distributions aren't exactly the same as spherical ones, but
spherical, which is equivalent to pointlike, can often be a good
approximation.

Im not familiar with his calculations ...

That last is a good summary of the problem. The people who do these
calculations understand them and their limitations and in particular
understand what the assumptions are, what the data imply, and what
remains uncertain. Various posts here have attempted to explain but
apparently haven't succeeded. Anyone who is still confused will just
have to learn the physics. It's not difficult at the level required,
but it does take proper study.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA

Steve Willner wrote...
orbit. How did Urbain le Verrier account mathematically for this
anomaly? By adding a small extra mass orbiting inside mercury`s orbit.

Small_ extra mass so as not to change the period or shape of the orbit,
only the precession of the nodes. Non-spherical mass distributions aren't
exactly the same as spherical ones, but spherical, which is equivalent to
pointlike, can often be a good approximation.

If spherical mass were equivelent to pointlike then Le Verrier could
have just added that very small (relative to the sun) mass to the suns
mass and explained the preccession using the point like calculation
for v. But he didnt because he had to make an n-body calculation
with that extra little mass outside but still near the sun to correctly
model the preccession.

Im not familiar with his calculations ...

That last is a good summary of the problem. The people who do these
calculations understand them and their limitations and in particular understand
what the assumptions are, what the data imply, and what remains uncertain.

You dont need to be familiar with his calculations to realize he couldnt
solve the preccesion problem with one point like calculation

Various posts here have attempted to explain but apparently haven't
succeeded

Those various posters you refer to didnt succeed because they didnt
understand the basics of physics. After all, none of them understand the
difference between a point like calculation and an n body calculation.
Despite my attempts to try to explain and to teach them.