The Circinus Galaxy

What’s so special about this galaxy?

Well, it’s the longest exposure I’ve ever taken (over two hours) but that’s not what I’m getting at.

At 10th magnitude, the Circinus Dwarf Galaxyan active galaxy, is a relatively bright object only 14 million light years distant, making it one of the closest galaxies to us, outside the Local Group.

So we should know a lot about it – but we don’t.

It’s quite astonishing that this object’s main claim to fame is that, despite its close proximity,  it was not discovered until 1977 – maybe a century or two later than most other comparable galaxies!

This is because its direction is in the plane of the Milky Way and as a consequence it is viewed through a rich Milky Way starfield. It is about 48° from the galactic centre and a mere 3° below the galactic plane.

The sheer number of stars and other material in the galaxy’s disc (possibly combined with its southerly latitude) must have led to it being overlooked.

It is a Seyfert type spiral galaxy, with a super massive black hole at its centre. This ten minute video explains a bit about it:

I understand that this galaxy was discovered here in Australia using the 0.5m Uppsala Telescope, then at Mt Stromlo Observatory near Canberra but now one of many telescopes located at Siding Spring Observatory near Coonabarabran, NSW. 

There are so many stars in my two hour exposure (FOV: approx 1.3° x 0.9°) that this image became the first of mine which Astrometry.net failed to identify.

I told you we don’t know much about it!


Object Details:

Designations: Circinus Galaxy; Circinus Dwarf Galaxy;  ESO 97-G13;  LEDA 50779;  PGC 50779;  ESO-LV 970130, IRAS 14092-6506;  2MASS 14130990-6520204.
Constellation:
Circinus.
Visual magnitude: 
+10.5
Apparent size: 
8.8′ x 4.3′
Diameter: 
35,000 light years. (about 20% of Milky Way diameter).
Distance: 
14,000,000 light years (about 70 Milky Way diameters).
Altitude during exposure:
40° above SSW horizon.
Also in image:
The Milky Way galaxy.


EDIT:
Image of Circinus at different wavelengths  ©The Royal Astronomical Society (Koribalski & Jarrett (2012))

Large-scale HI structure of the Circinus Galaxy


Technical stuff follows.
Please feel free to jump to the end and like or comment.

Image:

Exposure:  84 x 89.4 sec =  125 min.
Gain: 270
Date:  2019-08-06
Location:  semi-dark rural.
Conditions:  clear.
Moon: 5 days old, set 11.00 pm

Processing:

Image acquisition:  SharpCap.
Method: Live stacked.
Darks: 10x
Image post-processing:  GIMP.
Cropping:   Yes, to centre target.
Sky:   0.29  e/pixel/s .

Gear:

Telescope: SkyWatcher Esprit  Type: 120ED triplet refractor
Focal: 840 mm F/7 Mount: SkyWatcher EQ6-R Pro
Camera: ZWO ASI 071 MC Pro
Type: CMOS 28.4mm 16 Mpx
Optical aids: Flattener: Y; filter: LP Guiding: No
Polar aligning: QHYCCD PoleMaster Polar Error: 00’ 22”

Geek Log:

[ZWO ASI071MC Pro]
Debayer Preview=On
Output Format=FITS files (*.fits)
Binning=1
Capture Area=4944×3284
Colour Space=RAW16
Hardware Binning=Off
Turbo USB=40
Flip=None
Frame Rate Limit=1 every 4 seconds
Gain=270
Exposure=89.375778
Timestamp Frames=Off
White Bal (B)=50
White Bal (R)=53
Brightness=40
Temperature=-3.9
Cooler Power=100
Target Temperature=-15
Cooler=On
Auto Exp Max Gain=300
Auto Exp Max Exp M S=30000
Auto Exp Target Brightness=100
Mono Bin=Off
Anti Dew Heater=Off
Banding Threshold=35
Banding Suppression=0
Apply Flat=None
Subtract Dark=C:\Users\Roger\Desktop\SharpCap Captures\darks\ZWO ASI071MC Pro\RAW16@4944×3284\89.4s\gain_270\dark_10_frames_-0.8C_2019-08-06T09_39_54.fits
#Black Point
Display Black Point=0.01953125
#MidTone Point
Display MidTone Point=0.340754725333788
#White Point
Display White Point=0.998046875
TimeStamp=2019-08-06T11:35:49.9274014Z
SharpCapVersion=3.2.6062.0
TotalExposure(s)=7507.565352
StackedFrames=84


Image © Roger Powell


 

9 Comments

  1. I can see how that thick population of stars made discovering difficult. Nice job with locating and imaging it. I know very little about the process you use for such long exposures. You said it was about 2 hours. Is that one long exposure or is it many short ones gathered over 2 hrs then stacked? A 2 hr exposure would require exact alignment.

    Like

  2. I’m still refining my polar alignment technique, Jim. It’s never been one of my strengths.This night it was a decent 22 arc-sec but it’s not always that accurate, for various reasons.

    As I have abandoned auto-guiding, the sub-frames need to be short enough to eliminate star trailing and this can be done with a low noise CMOS camera chip.

    The final image was composed of 84 x 89.4 second subs totalling 125 min overall. The image is live-stacked so I can watch it slowly building up.

    👀

    Like

    1. I wouldn’t mind getting my hands on the Spitzer controls for a week or two, to view objects 11.5 billion light-years away. That would be exciting. I understand that it will be retired when replaced by the James Webb telescope, so why not give amateurs a go? 😂

      Liked by 1 person

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