Re: Seeing in the Dark

oriel36 <geraldkelleher@xxxxxxxxx> wrote:
On Sep 22, 5:55 am, br...@xxxxxxx (Brian Tung) wrote:
Margo Schulter wrote:

One more: William
Herschel may have observed spiral galaxies, but he did not identify
them as such--their spiral nature was not discovered until Lord Rosse
sketched M51 in 1845--some two decades after Herschel's death.


Galaxies were first observationally observed ,as such,in the mid
1920's and Rosse only identified them as spiral nebulae ,read it
yourself unless you have a severe reading disability aloing with an
intellectual and intutive one -

Hello, there, Gerald.

Here I would take Brian to be saying that William Herschel may have
observed objects now recognized as spiral galaxies, but that their
spiral nature was discovered by Lord Rosse in 1845, not necessarily
their nature as galaxies.

In fact, the "island universe" interpretation for some of these bodies
(itself a term of Kant) is nicely presented by William Herschel,
although he doesn't happen to use the word "galaxy."

"In 1845, Lord Rosse constructed a new telescope and was able to
distinguish between elliptical and spiral-shaped nebulae. He also
managed to make out individual point sources in some of these nebulae,
lending credence to Kant's earlier conjecture."

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

What this means is that in 1920 they knew nothing of these massive
rotating stellar islands,in fact they went out of their way to reject
such notions in 1920.I think it is the most hilarious prediction in
all my time dealing with the material but then again,it takes an
astronomer toi know what is being said -

Read the Shapley-Curtis debate of that era and you'll see that Curtis
views spiral nebulae precisely as external galaxies, with Shaplow
acknowledging the attractions of his opponent's views in this debate,
but arguing that other factors make this interpretation less likely.
It turns out that Curtis was right about the nature of the spiral nebulae,
but Shapley right as to the generally greater scale of the Milky Way
itself.

By the way, while the debate was an engaging and lively one, both
of the participants acknowledged some value in the other's contribution.
As it turned out, Hubble and others would use the Cepheid yardstick in
the following decade to resolve the issue; but this marked the point
at which "spiral nebulae as external galaxies" became the generally
accepted view, not then that view was first conceived.

Most appreciatively,

Margo Schulter
mschulter@xxxxxxxxxx
Lat. 38.566 Long. -121.430

.

Relevant Pages

  • Re: Seeing in the Dark
    ... them as such--their spiral nature was not discovered until Lord Rosse ... their nature as galaxies. ... views spiral nebulae precisely as external galaxies, ...
    (sci.astro.amateur)
  • Re: Seeing in the Dark
    ... them as such--their spiral nature was not discovered until Lord Rosse ... Galaxies were first observationally observed,as such,in the mid ... 1920's and Rosse only identified them as spiral nebulae,read it ... She was not saying anything that disagreed with that - Lord Rosse, ...
    (sci.astro.amateur)