NGC 346 & NGC 371 in the SMC

Object Details:

Designation:  NGC 346   Constellation:  Tucana     Visual magnitude:   +10.3
Apparent size: 14′ x 11′  Diameter: 1149 light years.  Distance: 200,000 light years


A large bright nebula, which is a long way away!

NGC 346 is located in another galaxy, the Small Magellanic Cloud (SMC). Many of the stars in this image are also in the SMC galaxy and one of the brightest of them all, HD 5980, is actually visible in the centre of this nebula.

Here is a blow up (in future: literally) of NGC 346 showing HD 5980:

3741550 cropped to NGC 346 & HD5980
Image cropped to NGC 346 & interesting multiple star system HD5980. On the right, IC1611 & IC1612 are both open clusters in the Small Magellanic Cloud. (Image: R.Powell. Identifiers: Astrometry.net)

HD 5980 is a multiple star system. To quote Wikipedia:

HD 5980 has at least three components amongst the most luminous stars known: the unusual primary has a Wolf–Rayet spectrum and has produced a luminous blue variable (LBV) outburst; the secondary, also a Wolf–Rayet star, forms an eclipsing spectroscopic binary with the primary star; and a more distant O-type supergiant is also likely to be a binary.

Gosh, a stellar system with two eclipsing Wolf-Rayet stars – plus an O-type supergiant which orbits the two WR stars. What a fascinating system that would be for a physicist to study!

Wolf-Rayets are extremely hot stars, up to about 210,000° K  (our Sun is about 6000°K), depleted of hydrogen, and with very strong stellar winds. O type stars are also very hot. So all three stars have a short life-expectancy and each will ultimately go supernova. Not a good star system to reside in.

The SMC itself is one of our closest galaxies, gravitationally bound to the Milky Way. With a declination of -72°, it is only fully visible in the Southern Hemisphere, although theoretically visible as far north as +18°. It’s seen as a misty patch, about 5° wide (six Moon widths).

Here in SW Sydney the SMC is circumpolar (never sets) and looks like a piece of Milky Way that has broken away.

Also in image:
NGC 371, a hexagonal looking open cluster, with a diameter of 434 light years.

3741550 cropped to NGC 371
NGC 371 is listed as an open star cluster but the nebula is obvious, always reminding me of a hexagonal nut. (Image: R.Powell. Identifiers: Astrometry.net)

NGC 299, NGC 300, NGC 361, NGC 376, NGC 395, NGC 416.

IC 1611, IC1612.

See my above image with Astrometry.net annotated overlay.


Technical stuff:

Image & Processing:

Date:  2019-11-07
Exposure:  32 x 89 sec  =  47 min.
Gain:   68

Location:  outer suburban.
Conditions:  clear sky, bright Moon
Sky brightness:   0.78 e/pixel/sec . 

Image acquisition:  SharpCap.
Method: Live stacked.
Darks:  6x

Image post-processing:  GIMP.
Cropping: no

Gear:

Telescope: SkyWatcher Esprit  Type: 120 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: Yes/No
Polar aligning: QHYCCD PoleMaster Polar Error: 2’ 25”

Geek Log:

[ZWO ASI071MC Pro]
Debayer Preview=On
Pan=0
Tilt=0
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=4 fps
Gain=68
Exposure=88.871802
Timestamp Frames=Off
White Bal (B)=50
White Bal (R)=53
Brightness=8
Temperature=-10.5
Cooler Power=92
Target Temperature=-10
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=On
Banding Threshold=35
Banding Suppression=0
Apply Flat=None
Subtract Dark=C:\Users\Roger\Desktop\SharpCap Captures\darks\ZWO ASI071MC Pro\RAW16@4944×3284\88.9s\gain_68\dark_6_frames_-10.0C_2019-11-07T10_56_03.fits
#Black Point
Display Black Point=0.0238095238095238
#MidTone Point
Display MidTone Point=0.547619047619048
#White Point
Display White Point=1
TimeStamp=2019-11-07T11:51:48.8458556Z
SharpCapVersion=3.2.6086.0
TotalExposure(s)=2843.897664
StackedFrames=32

Images © Roger Powell

2018-03-10 Telescope & Roger


 

 

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