Barred Spiral Galaxy
|Apparent magnitude: +10.3|
|Apparent dimensions: 11.2 x 6.2 arc-minutes|
NGC 1365 is a barred spiral galaxy, 56 million light years away. It is a bit larger than the Milky Way and at 200,000 light years diameter is comparable in size to our more well known neighbouring galaxy, M31 in Andromeda.
Note the two main spiral arms, emanating from a large bar which also contains the nucleus (which also show a hint of being a bar within a bar).
Galaxies come in several shapes and sizes. Commonly they are classified as elliptical, spiral or irregular. Spiral galaxies are further subclassified as either barred or unbarred or even a mix of the two.
NGC 1365 is classified as type SBb and is one of the finest of barred spirals. For comparison, the Milky Way is classified as type Sb although it, too, does have a small bar.
NGC 1365 is also a Seyfert type galaxy: a luminous nucleus, with very high surface brightness and spectra revealing strong, high-ionisation emission lines. It’s also been a happy hunting ground for supernova researchers – four have been detected over the last 64 years (1957, 1983, 2001 and 2012). Here in the Milky Way it’s been over four hundred years since the last bright local supernova was detected (1604). I guess the odds must increase with larger galaxies.
To the left of NGC 1365, nearly halfway to the edge of the image, lies another small galaxy, which I identified as 6dFGS gJ033312.8-360103. (Great name isn’t it? “6dFGS” is the name of the survey – the six degree Field Galaxy Survey. I’m not sure about “gJ” but it’s possibly identifying the epoch. The remaining numbers are simply the RA and DEC coordinates in the sky).
I was expecting 6dFGS gJ033312.8-360103 to be a very distant “background” galaxy but when I checked, I found that it has a spectroscopic redshift of just 0.004024. This equates to a distance of around 56 million light years – which is the same distance as NGC 1365 itself. So – surprisingly – it appears to be a much smaller galaxy in the same galaxy cluster as NGC 1365!
|Image exposure: |
|Image field of view: |
38.9 x 25.7 arc-minutes
|Image date: |
At 41 minutes, this exposure was not really long enough. I was hoping for at least two hours but astronomy opportunities are restricted by late sunset times and adverse weather conditions. Summertime and daylight saving delays the start time for imaging considerably, compared to winter. When clouds materialise during a session, it can mean loss of target and/or havoc in the guiding system. All these things happened this time around and I was back indoors early.
Images © Roger Powell
|Telescope:||Meade LX-90 200mm Schmidt-Cassegrain ; |
2000 mm f/l @ f/10 (deforked).
|Optics:||Astronomik light pollution filter.|
|Mount & Guiding:||SkyWatcher EQ6-R Pro mount.|
|Imaging camera:||ZWO ASI 071 MC cooled.|
Cosmic Focus Observatory
Above us only sky….
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