NGC 6357

Exposure: 75 minutesField of View: 1.57 ° x 1.01 °Image date: 2021-06-12

The Lobster Nebula

A one and a quarter hour exposure in H-alpha of this nebula in Scorpius fitted very nicely into my telescope’s field of view. It is known as the Lobster Nebula or the War and Peace Nebula. It looks more like a crab or some sort of bug to me.

My Sky Safari app describes the object:

“The surrounding nebula holds a complex tapestry of gas, dark dust, newly born stars and stars still forming. Intricate shapes in the nebula are carved by interstellar winds and energetic radiation from these young stars. The nebula also contains dusty pillars of molecular gas, likely hiding massive protostars shielded by dark discs of gas; and young stars wrapped in expanding “cocoons”.

This nebula spans four hundred light years and is known to be the most prolific region in our galactic neighbourhood for forming massive class O stars and Wolf-rayet stars, exceeding two hundred solar masses.

Magnitude: +10Distance: 5,900 light years.Apparent size: 50′ x 40′

Galactic Neighbourhood

Speaking of our neighbourhood, whilst nebulae like NGC 6357 are suitable places to look for hot, high mass class O and B stars, our more sedate region is not.

A consortium of European astronomers, compiled a Survey of every known star and brown dwarf within a small radius of 10 parsecs (33 light years) from the Sun. They found 422 stars, identifying them by spectral type, from high mass to low mass as follows:

  • Class O (very high mass hot blue-white) stars : 0
  • Class B stars: 0
  • Class A stars: 4
  • Class F stars: 8
  • Class G (medium mass Sun-like) stars: 18
  • Class K stars: 38
  • Class M (very low mass cool red dwarf) stars: 249
  • Class L, T, Y & D (dim brown dwarfs): 105 discovered so far.

The list is bottom heavy!

While our star, the Sun, is certainly a mid-mass, mid-temperature star, classifying it as “average”, is misleading. The most predominant stars by far are red dwarfs and brown dwarfs (many of which may remain un-discovered because they are so dim).

Red dwarf stars (60% of the total) are well known for their dramatic flare outbursts, making them unlikely places for planets where life evolves.

Brown dwarfs (25%) are probably in the same category but for different reasons. They are not really stars because nuclear fusion never occurred and they are too cool to foster life on nearby planets.

The take-home conclusion is that more than 80% of stars are unlikely places to harbour planets which may evolve advanced life-forms. The chances of other advanced civilisations evolving in our neighbourhood at this time seem very remote.

Location of NGC 6357

Position of Scorpius in the whole sky (left) and NGC 6357 in Scorpius (right)

nova.astrometry.net

If the Astrometry images do not appear it is because the Astrometry website is sometimes off line.

Thanks for reading 🙃


Telescope & Imaging Details

Telescope:SkyWatcher Esprit 120 mm apochromatic 3-element refractor; 840 mm f/l @ f/7.
Optics:Field flattener; ZWO Duo-band Hα (656nm) and [OIII] (500nm) filter.
Mount & Guiding:SkyWatcher EQ6-R Pro mount; ZWO ASI120 guide camera.
Imaging camera: ZWO ASI 071 MC Pro (CMOS 28.4mm 16 Mpx).
Software:Control: Cartes du Ciel, ASCOM, EQMOD, PHD2. Imaging: SharpCap, Gimp.
Observatory:34° South.

Images © Roger Powell

I’m one of the founder members of Macarthur Astronomical Society and current webmaster.

15 Comments

  1. Omgosh you take such beautiful photos, you really must publish it all in a book for us less talented star gazers. I’m sure the Campbelltown and Camden tourist info centres would happily consider selling such a book of locally taken photographs!

    Liked by 1 person

    1. That’s a very wonderful comment, thank you very much. I don’t have many locals following my photo-blog, so I appreciate it even more.
      A book? Well, you never know……

      Like

  2. Beautifully imaged. If you had not told me the name, I doubt if I would imagine lobster or crab. But the power of suggestion in the name makes a crab appear. … I agree with your assessment of the star populations around the Sun. Learning more about dwarf star populations with modern detection tools is shifting the odds for life downward. … Last evening just before 9:30 my wife and I walked a couple of blocks. It was the perfect temp. The sky was very clear. The Moon, Mars, and Venus were aligned across the evening sky. Nice view.

    Like

    1. My guess is that if life forms exist out there, the they will most likely be found in mid-range star systems, Classes F,G & K. – and they only represent about 15% of the population.

      The mouse plague here in Oz has been going on for years on country properties but appears to be getting worse. The big problem is that poisoning them has ramifications for other species too.

      Like

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