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Object of the Week July 24th, 2016 - M16 and the Pillars of Creation
M16 and the Pillars of Creation
Type: Open Cluster with Emission Nebula and Dark Nebula
RA: 18h 19'
Dec: -13 47'
Size: 35' x 25' (Brightest part of nebula)
Mag: 6.0
We deep sky observers sometimes crave for the hardest, faintest, most difficult targets for our telescopes, and we tend to forget that some of the most delightful objects are just there, laying ready for exploration, but totally ignored by us as they are “easy”, “well known” etc. And when we “stumble” on these neglected (but well known) objects we just stand there in awe, wondering how we could possibly have missed them! This is how this week’s object was actually chosen…
During the previous new moon period, I identified some possible targets for my next OOTW installment. They were very nice and interesting, albeit generally unknown objects. But I had to wait for them to rise somewhat higher, and at the same time I needed some time to improve my dark adaptation. So I started panning around the Sagittarius area, visiting good old favorites. M22, M24, M17, and finally M16. M16 – WOW! I had seen M16 before, but I had never OBSERVED it!! A huge difference and an important lesson for us! What was to be a quick tour of favorite objects became a week-long study of a single object!
But before I describe observationally this object, let’s study a bit its long history and the modern astrophysics. The object known to us as M16 was first observed by de Chesaux in 1746. Messier included it as the sixteenth object in his catalog, describing it as a cluster of small stars mingled with faint nebulosity – a spot-on description. Modern astrophysicists soon described M16 as star-formation area, a huge area of nebulosity with a cluster of young stars involved. M16 though became really famous to the general public when the Hubble Imaging Team released its famous photo of the “Pillars of Creation”. Huge columns of dark material, five to six light years long, standing dramatically in the center of the bright nebula, creating an unbelievably eerie starry scene as a result of hot hydrogen gas expanding into cooler gaseous regions. The dark pillars were identified long ago in deep photographs of the nebula, and Burnham, in his Celestial Handbook, gave them the title of the “Star Queen and her Throne”, using an amazingly poetic prose. The nebula of M16 is just the brightest part of an extensive nebulous cloud which seems to form one giant nebulous cloud, connecting with M17 further south. Today, the M16 complex is a popular target for astrophotographers, but what about visual observations?
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The whole M16 area. Photo by Bill Snyder Astrophotography
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Pillars of Creation. Photo by ESA - Hubble.
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M16 as imaged by the author.
Most visual observers mention that while the star cluster is quite obvious, the nebulosity is quite faint compared to the nearby bright nebulae like M8, M20, or M17, and filters do help a lot. And most observers consider the “Pillars of Creation” as an extremely difficult object, usually reporting it as an ill-defined triangular dark spot, if seen at all. But is it really so hard? When I “rediscovered” M16 three weeks ago, it was mainly the “Pillars” that got me so excited about this object. The “Pillars of Creation” appear as a dark nebula anchored next to two 9th magnitude stars almost at the brightest part of the nebula.
So, what can be seen with a telescope? Using my 18” Obsession without filters, the nebulosity was quite faint and soft, but could readily be discerned, especially to the west of the cluster. The general shape of the nebulous area could indeed be liked with an eagle with outstretched wings and a turned head. The brightest part of the nebulosity was located in the “neck” area, adjacent to two stars, and with some care, an ill-defined triangular dark area could be discerned next to two 9th magnitude stars.
An OIII filter changed the appearance of M16 quite a bit. The nebula appeared quite more distinct and well defined, and seemed now to extend more than without filters. The “Pillars” area also stood out better, appearing as a dark “V” shaped notch, which at times appeared sharp and at times appeared soft.
Changing to a UHC filter, the overall picture became even more impressive. The nebulosity appeared even brighter, with well defined edges to the east, and a gradual soft fading in the other directions. What’s more, towards the west, a strange striation pattern could be glimpsed at times, appearing like indistinct waves on a remote beach. These striations reminded me a lot of similar striations appearing at times over IC434 in Orion. But perhaps the greatest change was the appearance of the “Pillars” area and of the other dark nebulosities. Unlike the “V” shape evident with the OIII filter, now I could discern easily the whole “Throne and Queen” pillar, black as ink, illustrated against the bright nebulosity. The indistinct “V” shape became a very distinct “N”. In addition, the smaller pillar to the east, which appears in most photos as “hitch-hiking” on the bigger pillar was also very well defined, with a strip of bright nebulosity separating it from the bigger pillar. The whole area when seen in the eyepiece acquires a 3-D effect, with the black pillars appearing to stand in front of the bright nebula. It was this majestic appearance of the pillars area that so much impressed me that I kept returning to M16 night after night. Up until that moment that I observed M16 with a UHC filter, I had never noticed the pillars as such, and to be honest, I did not expect they would be so clearly visible in a telescope. The Pillar formation that I saw is not far from what can be recorded photographically. I re-observed M16 for three consecutive nights, and the view with the UHC filter was plainly fantastic. I have to admit that seeing the actual “Pillars” made me tremble with all sorts of emotions, and especially awe. I felt a tear or two wetting my eyes!
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In addition to the “Pillars”, I spotted another dark cloud protruding in the nebula from the west, and this corresponds well to the “Black Pillar of smoke” described by Burnham (and illustrated in page 1791 of his “Celestial Handbook”). A third spindle-shaped dark nebula seemed to be present at the northwest edge of the nebula, and again this dark cloud corresponds to another of the dark formations which are so plainly visible in photographs. Neither the “Black Pillar of Smoke”, nor the dark “Spindle” were visible without filter and were only suspected with the OII filter.
The huge improvement of the appearance of M16 with the UHC filter over the OIII prompted me to try the nebula with my H-beta filter as well. To my surprise, the image was not bad at all. I could see quite a bit of nebulosity, and the western part was especially pronounced. The “Pillars” area was better with the H-Beta filter than with the OIII, as I could see the “N” shape, though I could not see the smaller pillar. The contrast of the pillars though was lower than with either the UHC or OIII filters.
Independently of the filter used, with my 18” Obsession, the best image was obtained at 129X with my 13mm Ethos. With the 21mm Ethos or 31mm Nagler the nebula did appear brighter, but the relatively small size of the nebula (35x25 arcminutes) means that most details were lost. Even with the UHC filter the “Pillars” area was visible only as a tiny wedge. On the other hand, increasing the magnification decreased the contrast of the bright and dark areas of the nebula, causing the “Pillars of Creation” to be barely detectable with the UHC and OIII filters, and not visible with the H-Beta or without a filter. I suspect that the visibility of the Pillars is correlated with the exit pupil of the eyepiece used as is the case with other difficult dark nebulae, but I did not have the chance to test this idea with many eyepieces.
What about smaller apertures? M16 is readily visible in binoculars as a bright hazy patch, with pinpoints of starlight occasionally piercing the haze. I had a great view of the nebula with my 22x60 binoculars, the “eagle” shape being evident. Using my refractors, the results were pretty similar with 4, 5, and 6 inches. Without a filter, the bright nebula was very soft and faint but readily detectable, though the “Pillars” area was only suspected as a “shadowy” patch of undetermined shape. Again, the UHC filter worked best, the OII was ok, but the H-Beta did not improve the contrast of the nebulosity. With the UHC and OIII filters the “Eagle” shape was readily apparent, and the “Pillars” area assumed a tiny but distinct dark wedge shape. Using my 6” achro (F.L. 900mm) and my 4” APO (F.L. 820mm) the best image was obtained using the 13mm Ethos (69X and 63X respectively), but the image was quite good with the 7mm Nagler as well (128X and 117X respectively. Using my 5” achro (FL 600mm) the best image was with the 7mm Nagler (85X), the other eyepieces giving too small a magnification for decent details). I did not have as much time as I would like to spend on M16 with the refractors, I believe that at least with the 6” it might be just possible under very dark conditions to spot the whole “Pillar of Creation” structures, and possibly even the “Black Smoke Pillar”.
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A challenge for those with big (and huge) scopes might be to spot the longest of the three pillars imaged by Hubble. This pillar seems to be hidden in the “glare” of the two 9th magnitude stars that anchor the “Pillars of Creation” structure even in photographs, so actually seeing it visually should be a great challenge. You now know what my aim will be on the next new moon!
As a final note, keep in mind that spotting the “Pillars of Creation” is a good practice for people who aspire to observe visually the best known dark nebula, the Horsehead Nebula. If you manage to see the dark wedge in the heart of the bright nebula, then you start to get an idea on what you should expect to see in the Horsehead. Except that the Horsehead is considerably larger and the background nebula significantly fainter. But still, seeing the Pillars is a good practice for this most sought after dark nebula.
So, during the evenings of the next new moon period, when you turn your scope towards the Milky Way, remember M16 and all its wonderful challenges and plan to really spend some time on it!
So, next time you are out,
GIVE IT A GO AND LET US KNOW!!!
