Re: Two Studies (Andromeda Rotation)
From: greywolf42 (mingstb_at_marssim-ss.com)
Date: 06/28/04
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Date: Mon, 28 Jun 2004 13:49:56 -0700
greywolf42 <mingstb@marssim-ss.com> wrote in message news:...
> Bjoern Feuerbacher <feuerbac@thphys.uni-heidelberg.de> wrote in message
> news:cbh14n$g23$1@news.urz.uni-heidelberg.de...
> > greywolf42 wrote:
> > > Bjoern Feuerbacher <feuerbac@thphys.uni-heidelberg.de> wrote in
> > > message news:cbbnf3$l30$1@news.urz.uni-heidelberg.de...
{original statement}
"Geometry is claimed from 'direct measurement of orbital motions in a disk
of gas surrounding the nucleus of this galaxy.' How many people remember a
similar claim about the detection of actual motion in the Andromeda galaxy,
years ago?"
{snip down to Andromeda issue}
> > >>>Do you admit to ignorance about the publication of observation of
> > >>> proper motions in the Andromeda galaxy?
> > >>
> > >>Yes, I admit my ignorance about this.
> > >
> > > Fair enough. I'll dig around and find it. (It was in the '20s, if I
> > > remember rightly).
{snip}
> I will attempt to find the reference for the Andromeda rotation.
> (Which may not occur until next week, as I'm about to depart for the
> weekend.)
I quote from the text "Galactic Astronomy, Structure and Kinematics,"
Mihalas and Binney, second edition, 1981, pages 8 and 10:
"In April, 1920, (H.D.) Curtis and (H.) Shapley met at the National Academy
of Sciences in what has since been called astronomy's GREAT DEBATE. On this
occasion, two primary problems were discussed: (1) the size of our Galaxy
and the distance scale within it, and (2) the distances of the sprial
nebulare and, by implication, the question of whether or not they are
extragalactic systems." (italics in original as capitals)
"Measurements of proper motions in spiral nebulae by A. van Maanen indicated
that the spirals rotate with an angular motion of 0".02 per year. For any
plausible rotation velocity, this implies that the spiral nebulae must be
close. .... At the distances required by the view that the sprials are
separate galaxies, the velocities implied by van Maanen's proper motions
would be ridiculously large."
"The argument that probably had the greatest influence in forming the
opinion of the astronomical community at large was Shapley's point about van
Maanen's proper motion measurements. Van Maanen had an excellent reputation
as a meticulous observer and enjoyed the general respect of the community;
hence his results were almost universally accepted as correct.
Unfortunately, they were purely and simply spurious -- the rotational proper
motions of spiral galaxies are in fact too small to measure, even by the
most accurate present-day techniques. But definitive proof that van
Maanen's work was in error did not emerge for another fiteen years after the
Curtis-Shapley debate. Even today we cannot reconstruct unewquivocally the
causes of the errors in his results. [See Berendzen, Hart, and Seeley,
1976, 'Man Discovers the Galaxies'; for an interesting analysis of this
matter]. The great debate itself settled neither of the questions it
addressed, and opinions remained sharply divided. It did, however, bring
the issues into sharp focus, and it stimulated a great deal of thought."
{snip the rest}
--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail}
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