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NET Angular Momentum of Globular cluster of stars



 
 
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Old March 27th 17, 05:28 AM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
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Default NET Angular Momentum of Globular cluster of stars

[[Mod. note -- I apologise to readers for the delay in processing this
article, which the author submitted on 2017-03-23. Unfortunately there
were some garbled characters in one of the article headers that took a
bit of time to straighten out.
-- jt]]

In article ,
writes:

On Tuesday, March 21, 2017 at 1:18:55 PM UTC-7, Steve Willner wrote:
In article ,
writes:
Is the NET angular momentum of a globular cluster of stars, zero?


OK, it can be difficult to communicate in words rather than pictures and
sketches.............trying again:

I'm just trying to get us on board for a qualitative exploration.


While a qualitative understanding is necessary, it is not sufficient. As
Lord Kelvin said, "I often say that when you can measure what you are
speaking about, and express it in numbers, you know something about it;
but when you cannot measure it, when you cannot express it in numbers,
your knowledge is of a meagre and unsatisfactory kind."

Sure,
with ellipticals, as with globulars, there is a range of oblatness to
the spherical geometry. A flattened structure may (and may not) have
net angular momentum, it depends on whether there are stars rotating in
a preferred (or in counter rotational
e.g. the spiral ngc4138 is counter rotating, so it's possible for stars
in ellipticals to also have this feature
https://en.wikipedia.org/wiki/NGC_4138)
directions about the flattened plane's normal axis. ie, we have E0
through E5 ellipticals.


Note that this refers only to the appearance. So if we look at
something cigar-shaped along the major access, or something shaped like
a disk along the minor axis, we see E0 in both cases.

BUT,

COMPARED TO.... a simple spiral disk, with no central bulge, with all
stars moving around a center in the SAME direction..........like
Saturn's rings. ........... an elliptical and or a globular have

ESSENTIALLY, ZERO angular momentum .


As has been noted here, this doesn't seem to be the case, based on
current observations. There seems to be an appreciable number of
"fast-rotating" ellipticals.

In other words, can we agree that if I have the same number of stars,
and the same orbital radii, ellipticity etc. for every star, with the
sole exception that the globular has stars that appear as spherical
morphology, where as a flat spiral has purely single angular momentum
axis.............

The globular will be nearly zero compared to the flat spiral.

Agreed? If so then I can move on.

rt

 




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