Now, before you folks across the pond from me start getting all patriotic when reading the post title, lighting fireworks and all: it's not the 4th of July, yet ;-)
Had it been, then I would better have picked a Green Rectangle (in Cygnus), as our OotW would have been below the horizon. Therefor, I chose to go with red instead.
The object is a (proto-)planetary nebula in Monoceros, the Unicorn, near the southern border with Canis Major. It surrounds the variable and double star V777 Monocerotis that shines at about mag. 8.8. The position is 06:19:58 -10d38m15s. It's best known as the "Red Rectangle" (Wikipedia).
This peculiar nebula was discovered in the early 1970's and not by using a ground based telescope but - believe it or not - by using equipment strapped to a rocket. An Aerobee rocket, to be precise. These were used in the AFCRL program, which stands for Air Force Cambridge Research Laboratories, later changed to AFGL (Air Force Geophysics Laboratory). Only after it was detected in the rocket program, it was recognised on Palomar plates. Follow-up research involved the Kitt Peak 4 meter reflector.
It's formal designation is AFGL 915, a.k.a PN G218.9-11.7 and IRAS 06176-1036. An image by the HST best reveals the nature of it's nickname but luckily, that does not mean it's out of reach of amateur aperture.
RedRectangle_HubbleSchmidt_1080.jpg
In the discovery paper the nebula is described as:
In the blue, a very weak amorphous nebula is present, very close to the star;
In the yellow, a bright, small elliptical nebulosity surrounds the star, and this oval structure is seen in the D-lines, whereas the spikes are not, only becoming visible in a broad filter;
In the red, the nebula shows an inner, bright, apparently rectangular core close to the star, with prominent bright spikes emanating symmetrically from its corners. Both rectangle and spikes are continuum features rather than line structure;
In the near-infrared the spikes are weakly visible.
The highly symmetrical appearance of the nebulosity is striking, and much detail is apparent beyond the bright rectangular core; for example, there is a second, fainter nebulosity present within the north and south quadrants which terminates sharply and linearly, parallel to the shorter edges of the rectangle. This fainter nebulosity meets the spikes at four small, bright knots which also limit the extent of the brightest portions of the spikes. The spikes persist beyond these knots but with a much reduced surface brightness.
The nebula is about 40" in N-S extent, although wispy extensions can be traced further out.
Using an observing guide similar to the one below (click here to download) I observed this nebula just over a year ago, from the French Alps.
AFGL 915_1.jpg AFGL 915_2.jpg
During that session, the skies were as good as they get in this part of the world. I played around with filters and magnifications to see what the "Lady in Red" would reveal of herself when observed in my 14" SCT. I can't add an SQM value for the observation as my SQM meter had gone haywire after the many sessions I used it since 2008; only so much freezing and thawing the electronics can take... Here's what I observed:
17mm Nagler T4 (168x / 29'): A pale orange mag. 9 star (V777 Monocerotis), quite a distinct orange hue, but no nebulosity is visible.
17mm Nagler T4, Lumicon UHC: Using this filter the star V777 Monocerotis remains visible, with AV a subtly north-south elongated shape is visible.
17mm Nagler T4, Lumicon OIII: Using this filter the shape is elongated NNW to SSE, visible without AV. Thereby the shape of the nebula is discernible. The star V777 Monocerotis remains notably bright with use of this filter.
12mm Nagler T4 (237x / 21') & 12mm Nagler T4, Lumicon UHC / OIII: As with 17mm. Unfiltered the nebula appears a bit ruddy but that is suspected to be due to the color of the star V777 Monocerotis.
7mm Nagler T6 (407x / 12'): Using this magnification and AV the nebula is clearly elongated NNW to SSW.
7mm Nagler T6, Lumicon UHC: Using this filter the nebula is elongated without use of AV and is subtly brighter in the middle.
7mm Nagler T6, Lumicon OIII: The effect of this filter is comparable to that of the UHC filter but is more subtle. The nebula is slightly less elongated.
3.5mm Nagler T6 (814x / 6'): Using this magnification the elongated shape of the nebula is discernible.
3.5mm Nagler T6, Lumicon UHC: Using this filter and AV the elongated shape is clear and the nebula is fainter to the ENE of the middle. There appears to be a knot on the SSW edge, which is notable.
3.5mm Nagler T6, Lumicon OIII: As with 3.5mm and the UHC filter the elongated shape of the nebula is clear and the nebula is fainter to the ENE of the middle. It is clear, too, that the nebula is slightly brighter on the western side in an elongated part aligned NNE to SSW. The suspected knot on the SSW that was visible with use of the UHC filter, is clearer with use of this filter.
A remarkable object.
Working out the observation I determined that the knot on the SSW edge is likely to be a faint star.
The song's lyrics are only fitting:
I've never seen you looking so lovely as you did tonight,
I've never seen you shine so bright,
I've never seen so many men ask you if you wanted to dance,
They're looking for a little romance, given half a chance,
And I have never seen that dress you're wearing,
Or the highlights in your hair that catch your eyes,
I have been blind;
Lady in red is dancing with me, cheek to cheek,
There's nobody here, it's just you and me,
It's where I want to be,
But I hardly know this beauty by my side,
I'll never forget the way you look tonight.
This time of year, with the skies of spring approaching fast, be sure to catch this nebula. It's positioned conveniently near the meridian at end of evening astronomical twilight.
In the vicinity: Only 1 degree east-northeast is another planetary - Minkowski 3-56. Be sure to also pan half a degree southeast of there to observe the reflection nebula(e) Dorschner-Gürtler 56.
Now give it a go, and let us know!
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