Cosmic Background Radiation

This message was posted to the Royal Astronomical Society of Canada members
newsgroup but I would like to see a response from a wider audiance so I'm
posting it to sci.astro.research.

Some time back I was looking through the RASC history book, "Looking
Up", by Peter Broughton and noted the article on Canadian astronomer, Andrew
McKellar where it stated that he was probably the first astronomer to
estimate the 3 degree cosmic background radiation 25 years before it was
measured. This was of course done by Arno Penzias and Robert Wilson from
Bell Telephone Labs in 1965 and measured at 2.7 deg K. I did a search for
more information on the internet and another author claimed the existence of
such radiation was first predicted by George Gamow in 1948. McKellar's
paper was published by the Department of Mines and Resources, Canada,
Publications of the Dominion Astrophysical Observatory, Victoria, B.C.
Volume VII, No. 15, in March 1941. He was studying spectroscopic plates
taken with the 100 inch at Mount Wilson noting sharp CH and CN lines in
stellar spectra. He stated that the three-prism spectrograph at Victoria
barely revealed these lines. From this McKellar stated that the temperature
was 2.3 deg K. compared with earlier temperatures estimated by Eddington,
(3.2 deg k.), for matter in interstellar space. Some have suggested that
this was over looked because it was published in an obscure Journal with
limited circulation! Obscure, perhaps in popular circulation, but not
overlooked. See the book, "Astronomical Spectroscopy" by A. D. Thackery
(1961) on p. 148.
I have read McKellar's paper and am first to admit that much of this is
way over my head. Perhaps one of our professional spectroscopists can
simplify this so a lay person can understand this better. I do think that
McKellar's work should be given more historical credit than it is. Any
comments?

Ed Majden
Courtenay, B.C.

Ed Majden wrote:
This message was posted to the Royal Astronomical Society of Canada members
newsgroup but I would like to see a response from a wider audiance so I'm
posting it to sci.astro.research.

....snip summary of McKellar's results on what turned out to be the CMB...

I have read McKellar's paper and am first to admit that much of this is
way over my head. Perhaps one of our professional spectroscopists can
simplify this so a lay person can understand this better. I do think that
McKellar's work should be given more historical credit than it is. Any
comments?

I'm not so sure about "overlooked" - this work is regularly cited
as an interesting historicl aspect of CMB studies. In fact,
up through the 1970s, followup remained a serious piece of CMB
research, affording access to the one relevant wavelength for
CN excitation across the Galaxy. (In fact, it was intellectually
important as the first evidence that the microwave background
couldn't be a very local phenomenon - sort of the role now played
by C II excited state absorption in QSO absorption lines by
tracing the implied CMB temperature with redshift). I learned
about it from an oldish Annual Reviews article, and am pretty
sure it's detailed in Bruce Partiridge's book (since our library
didn't see fit to buy one...)

To complicate things further, one of the Mt. WIlson spectroscopists
(Adams?) was described as having noted the excess CN temperature about
teh same time. A quick ADS search does show Adams as observing
CN lines, if only because are in the same spectral range as the
Ca II H and K lines he was surveying. McKellar was not exactly
an unknown in astronomical publication - I see here his paper
on the identification of CN as the first known interstellar
diatomic molecule in a 1941 PASP paper, for example. His
interests moved on to cometary spectra and molecules in stellar
atmospheres after the war years. One thing that can be frustrating
for those of later generations (ahem) is that interesting
things can often be hidden in the more discursive papers
written back then, when there were fewer astronomers and
fewer papers tp plow through.

[[Mod. note -- A few minutes ago I mistakenly posted a version of this
article lacking a "References:" header. My apologies for the omission;
here is the full article again, this time hopefully with all headers...
-- jt]]

Ed Majden wrote:
This message was posted to the Royal Astronomical Society of Canada members
newsgroup but I would like to see a response from a wider audiance so I'm
posting it to sci.astro.research.

....snip summary of McKellar's results on what turned out to be the CMB...

I have read McKellar's paper and am first to admit that much of this is
way over my head. Perhaps one of our professional spectroscopists can
simplify this so a lay person can understand this better. I do think that
McKellar's work should be given more historical credit than it is. Any
comments?

I'm not so sure about "overlooked" - this work is regularly cited
as an interesting historicl aspect of CMB studies. In fact,
up through the 1970s, followup remained a serious piece of CMB
research, affording access to the one relevant wavelength for
CN excitation across the Galaxy. (In fact, it was intellectually
important as the first evidence that the microwave background
couldn't be a very local phenomenon - sort of the role now played
by C II excited state absorption in QSO absorption lines by
tracing the implied CMB temperature with redshift). I learned
about it from an oldish Annual Reviews article, and am pretty
sure it's detailed in Bruce Partiridge's book (since our library
didn't see fit to buy one...)

To complicate things further, one of the Mt. WIlson spectroscopists
(Adams?) was described as having noted the excess CN temperature about
teh same time. A quick ADS search does show Adams as observing
CN lines, if only because are in the same spectral range as the
Ca II H and K lines he was surveying. McKellar was not exactly
an unknown in astronomical publication - I see here his paper
on the identification of CN as the first known interstellar
diatomic molecule in a 1941 PASP paper, for example. His
interests moved on to cometary spectra and molecules in stellar
atmospheres after the war years. One thing that can be frustrating
for those of later generations (ahem) is that interesting
things can often be hidden in the more discursive papers
written back then, when there were fewer astronomers and
fewer papers tp plow through.

[[Mod. note -- My new usenet server requires a valid domain on the
"From:" line of all outgoing articles, so I had to edit the sender's
anti-spam address. My apologies for any extra spam this lets through...
-- jt]]

Ed Majden wrote:
[...]
I have read McKellar's paper and am first to admit that much of this is
way over my head. Perhaps one of our professional spectroscopists can
simplify this so a lay person can understand this better. I do think that
McKellar's work should be given more historical credit than it is. Any
comments?

You might want to look at a recent book by Alpher and Herman, _Genesis
of the Big Bang_. The authors were intimately involved in the early
history of the CMBR. Chapter 5 has a discussion of the history, and
includes a couple of pages about McKellar.

Steve Carlip

[[Mod. note -- I have reformatted the text slightly to make it clearer
who said what. -- jt]]

Ed Majden wrote:
[...]
I have read McKellar's paper and am first to admit that much of this is
way over my head. Perhaps one of our professional spectroscopists can
simplify this so a lay person can understand this better. I do think that
McKellar's work should be given more historical credit than it is. Any
comments?

Steve Carlip wrote
You might want to look at a recent book by Alpher and Herman, _Genesis
of the Big Bang_. The authors were intimately involved in the early
history of the CMBR. Chapter 5 has a discussion of the history, and
includes a couple of pages about McKellar.

I haven't read the book which Prof. Carlip is refering to.
I also saw a good dsicussion of Mc Keller's work in the book by Hoyle, Burbidge
and Narlikar: A different approach to Cosmology