NGC 1365

2021-12-29 NGC 1365

Barred Spiral Galaxy

Apparent magnitude: +10.3
Apparent dimensions: 11.2 x 6.2 arc-minutes
Constellation: Fornax

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.

Galaxy classification.
(Wikimedia Commons).

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!

Exposure Details

Image exposure:
41 minutes
Image field of view:
38.9 x 25.7 arc-minutes
Image date:
2021-12-29

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 ยฉ 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.

The Blind Astronomer

Cosmic Focus Observatory

34ยฐ South

Above us only sky….

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14 Comments

  1. As an artificial measure of human-related time, I’m not sure how daylight saving affects observations.

    I assume you mean that because of the longer days, you have a smaller window for observations, regardless of the arbitrary answer to “what time is it?”

    Liked by 1 person

    1. Artificial but also real. As a layman I am happy living with daylight saving, as I have every year of my life – but as an astronomer I hate it.

      At this time of year the Sun would set at about 7.10 pm but with daylight saving that becomes 8.10 pm. If I want to pack up at midnight that still gives me four hours doesn’t it? Nope! Civil dusk is about 8.40 pm. Nautical Dusk is about 9.15 pm. Astronomical Dusk is about 9.55. In practice this means:

      About 9.00 pm the first stars are visible and I can begin polar aligning and about 9.45 pm, if I am quick, I can finish various other essential calibration tasks, locate and confirm my target and be ready to commence imaging by about 10.00 pm. So just two hours of imaging before midnight.

      (If I was prepared to keep going until dawn, then maybe DLS would not be such an issue!)

      ๐Ÿ™ƒ

      Like

    2. But, “midnight” โ€” as all others mentioned times โ€” is an artificial, human-centered measure of time and a self-imposed deadline.

      If Australia all of a sudden got rid of DLS, it wouldn’t change your apparent self-imposed limit of two hours of observations.

      Or is “midnight” an inflexible time limit regardless of when it occurs? What keeps you from observing for an extra hour?

      I mean, I don’t see why it has to be a binary choice โ€” midnight or dawn.

      There’s some wiggle room between those two.

      Like

    1. Yes, I did see that. It’s one of those outstanding discoveries which is a big leap forward in our knowledge of the Universe but which doesn’t really get the attention it deserves. I’m glad you picked up on it!

      Since Betelgeuse began dimming significantly over the last couple of years, I’ve asked several professional astronomers whether precursor stars provide any advance evidence of a supernova about to happen. Apart from the neutrino emission (only seconds before) I was told emphatically that we cannot know what is going on at the star’s core because it takes thousands of years for the photons to reach the surface.

      This discovery seems a game-changer!

      ๐Ÿ™ƒ

      Liked by 1 person

      1. ๐Ÿ™‚ You know, I was actually alarmed when that chatter about Betelgeuse was happening. I mean it would have been spectacular to witness the nova, but just think how misshapen Orion would like a few years hence. It was one of my favorite stars in childhood — the first one I could actually tell was a different color.

        It is mysterious to me how they were looking at this the precise moment it ruptured. It is amazing.

        Liked by 1 person

        1. Betelgeuse will blow up one day. Maybe the news is already on its way to us, if it happened in the last 500+ years. Fear not, it would be the most spectacular event which any of us could ever hope to see – and will almost certainly leave behind some fascinating visual evidence of it’s once glorious past. Probably a neutron star (or a black hole) and the glow of a fast expanding supernova remnant, like M1.

          I can’t wait…

          Liked by 1 person

  2. Beautiful capture, โ€ฆawesome background info and galactic descriptions. Years ago while finding and โ€œseeing โ€œ many (usually Messier) galaxies visually, it was thrill to just see a faint blur. It would have been far fetched to even dream of capturing these beautiful images by โ€œamateursโ€. Well done! M ๐Ÿ™‚

    Liked by 1 person

    1. Thanks, Marty. Yes, I remember seeing those faint fuzzies.

      A few years ago I never dreamed I would be capturing images of galaxies. There may have been some advancement in optics and perhaps a price reduction compared to what telescopes cost back then. However the big advancement has been the development of CCD cameras, followed by low-noise CMOS cameras. That, together with some incredible software applications which manage the imaging and improves target acquisition accuracy has made life much easier for amateurs.

      Like

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