Nebula NGC 1982 in Orion
| Image exposure: 75 minutes | Image field of view: 38.4 x 25.4 arcmin | Image date: 2022-03-09 |
Poor old M43, overlooked and neglected. No-one takes any notice of it!
The only claim to fame for this star forming cloud of ionised hydrogen is to be a mostly unnoticed comma shaped appendage on the edge of the famous Orion Nebula M42 – but if M43 were anywhere else in the sky it would surely be a popular target for amateurs.
It barely gets a mention in reference books and even the epic Burnham’s Celestial Handbook dismisses it with a scant reference in a lengthy description of the mighty M42.
M43 is about 1,300 light years distant and two light years in diameter. It actually has two zones, with a streak of dark nebulosity separating the bright comma from a much fainter adjacent cloud. It is surrounded by a number of stars of magnitude between +9.5 and +11.
The very bright star at the centre is magnitude +6.8 NU Orionis (SAO132328).
It is not to be confused with nu Orionis, a 4th magnitude spectroscopic binary star (SAO 95259) located elsewhere in the same constellation.
Who knew that two unrelated stars in the Orion constellation are called “NU” and “nu”? WHY do astronomers do this?
NU Orionis is part of a multiple star system and is a Type B eruptive variable star, the source of the ionisation which illuminates the nebula.
A part of the gigantic Orion Nebula M42 is seen above M43. Of particular note is the small four star arrangement know as the Trapezium, which Burnham describes as “the bright core of a compact cluster of faint stars”. It is located in the brightest part of M42 which often becomes an over-exposed casualty as amateur astro-photographers crank up the settings, in an attempt to capture the fainter surrounding nebulosity.
Here’s one I took earlier….
Roger Powell 2011-01-01
See what I mean? Even I found myself discussing aspects of M42, in a post about M43……..
šµ
| Telescope: | Meade LX-90 200mm Schmidt-Cassegrain (deforked); 2000 mm f/l @ f/10. |
| Optics: | Astronomik light pollution filter. |
| Mount & Guiding: | SkyWatcher EQ6-R Pro mount. |
| Imaging camera: | ZWO ASI 071 MC cooled. |
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I am curious. The dazzling pinks and magentas in the nebula in this image… is this actually what the eye detects through the instrument, solely due to sufficient magnification? Or is there some filtering process which is employed to ‘highlight’ the textural differences? I’ve long loved astronomy and the night sky — my whole life really — but never got into telescopy or astro-photography enough to understand these kinds of matters. If that color is ‘actual’ the the cosmos is even more spectacular than I thought.
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Those are very good questions. If you observe this object using an amateur telescope, you will most likely see it in black and white, which is how the human eye always interprets faint stuff. Coloured light needs to be more intense before it registers.
The nebula is mostly hydrogen gas. As you noticed, there are two principal colours in this image and as you would know, humans normally see things by light from the Sun or a room light etc which reflects towards us. The bluish hues come from starlight illuminating the hydrogen and reflecting as blue.
The dominant reddish hues are not produced from a reflection process. Inside the nebula, many hot young stars are radiating intense ultraviolet and this high energy causes the ionisation of the gas. So the gas itself is the light source, glowing at the specific emission wavelength of ionised hydrogen (656 nm).
Astronomers will often use filters in a way which produces false colours to accentuate contrasts in the image. However, the filter which I used for this image was designed only to block artificial light pollution and allow “natural” celestial light to pass through to the camera unhindered.
Thanks for asking. I hope that helps!
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“If you observe this object using an amateur telescope, you will most likely see it in black and white…”
I can 100% guarantee this description, as that is exactly how I saw it through my Dobsonian tonight. The main gas forms are noticeable but everything is a variety of grey.
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yes that is quite “illuminating” š thanks! really a very wonderful collection of hues.
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Stunning capture . . . as for M42 versus M43 . . . I mean, 42 is the Answer to the Ultimate Question of Life, the Universe, and Everything.
Surely, it deserves the spotlight.
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I never thought of that. Poor old M43, the odds are stacked against it.
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I had a good look at Orion last night including the Trapezium. I also hopped over to see the Winter Alberio 145 Cma.
I enjoyed your poem.
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I love a good double but haven’t observed it. Is it similar to Albireo in Cygnus?
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It is similar in colors, though not as saturated. The separation is 26″ compared to Alberio’s 35″. The pair is not a true binary.
https://rogerivester.com/2017/02/08/winter-albireo-h-3945-double-star-in-canis-major-february-observers-challenge-object/
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