November is the best month to observe our nearest large galactic neighbor, Messier 31. While M31 was observed and cataloged by Persian astronomers in 964, it was not recognized as an external galaxy until 1925, when Edwin Hubble observed a Cepheid variable star in the galaxy and was able to establish that the ‘nebula’ was definitively outside our own galaxy. Hubble’s work settled the ongoing ‘great debate’ about whether the observed spiral nebulae were part of our galaxy or were ‘island universes’ beyond it.
With its bright core, spiral arms and dark lanes of gas and
dust, it is a wonderful object for astro imagers. This image was taken with a narrowband
filter, which highlights red HII regions in the spiral arms. The large image
shows the whole galaxy and the crops of the spiral arms and core show some of
the wonderful detail in this object.
Tech card: RASA 8; DS10C; NBZ filter. The final image integration
time was 2.9 hours of 40 second subs.
Click on the images to see larger versions, then click again to zoom even further.
The bright, greenish patch at the 7 o'clock position is NGC 206, a bright region of star formation in M31 itself.
Details of the red H II regions and swirling dark dust lanes are visible in this crop of the core regions of the galaxy.
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