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Re: (IAAC) Blue spiral in Cetus (M77, NGC 1068)
At 11:13 PM 7/4/99 +0200, you wrote:
>Dear all,
>
>I wonder if anyone has ever attempted to observe the galaxy M77 (NGC 1068)
or more
>exactly its nucleus through a nebular filter. The galaxy is a well known
>representative of Seyfert galaxies with strong nuclear emission in the
forbidden blue
>green lines of ionized oxygen ([OIII]), otherwise typical of planetaries,
so I was
>quite surprised to read recently in the book 'Problem In Astrophysics' by
Agnes M.
>Clerke (1903):
>
>'Another object of dubious relationships [the description appeared in the
chapter
>'Nondescript nebulae'] is Messier 77 (N.G.C. 1068), Lord Rosse's "blue
spiral" in
>Cetus. The description intimates an anomaly, since true spirals are
"white," and give
>a continuous spectrum. Now the colour of this object corresponds, as might
have been
>expected, to a gaseous constitution, whether of the normal kind or in
certain ways
>peculiar, remains to be proved.'
>
>snip<
>As you can see, Lord Rosse commented on the galaxy's color only once, in
the first
>record, and later focused his attention on the morphology instead. It's
tempting to
>conclude that he saw the galaxy blue because of the [OIII] emission, but
one must
>keep in mind that while the lines are quite strong, most emission come from the
>central region a few arcseconds across so the story is no doubt just a
curiosity.
>Anyway, it should be interesting to try nebular filter (especially combined
with high
>power and aperture) on the galaxy's nucleus. Spectrum or photoelectric scan
published
>by Shields and Oke in ApJ 197:5, 1975 (Fig.2) suggests the filters should
work well.
>
>Clear skies,
>Leos Ondra
What is fun with M77 is to use a direct vision prism on it. I tried with my
20" and you could get a suggestion of the bright lines. I would like to
follow that up again when I have recemented the prism, which fell apart sadly.
Nick
Nick Martin, Bonnyton House, By Ayr, Ayrshire KA6 7EW ,Scotland, UK.
Latitude 55 24'56" Longtitude 4 26' 00".
"Eppur si muove" Galileo Galilei
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