Object of the Week August 11, 2013 - CED 211, R Aquarii

CED 211, R Aquarii

Aquarius

RA
23h 43m 49s

DEC
-15º 17' 04"

MAG ~7.5 (variable) for R Aquarii

Type: Symbiotic Star

CED 211 is one of the objects on my “save for steady seeing” list. Last week at the Oregon Star Party featured excellent seeing and I finally got a decent look at this intriguing object. I should note that the delay in getting this posted is because I returned from the OSP the evening of August 12 and discovered it was my turn to post the OOTW – sorry for the delay but the observing was awesome!

Here are my notes for CED 211 as it was nearing the meridian on the night of August 5th:

“Wow, this is really interesting! The star (R Aquarii) has a dirty, ruddy color to it at 155x but at 408x and 695x the color is washed out. The ‘star” of the show is the narrow streak of nebulosity that runs northeast to southwest, with a small knot on the northeast end. How cool is that!

The knot is best seen at 695x but is barely seen at 408x once I knew where to look. The northeast spike is brighter than the southwest counterpart, and the broadband filter (DGM’s galaxy filter) provides slightly more contrast. 2:21am, 21.76 SQM”

Wikipedia has this to say:
“R Aquarii is a symbiotic star believed to contain a white dwarf and a Mira-type variable in a binary system. The orbital period is approximately 44 years.[4] The main Mira-type star is a red giant, and varies in brightness by a factor of several hundred and with a period of slightly more than a year; this variability was discovered by Karl Ludwig Harding in 1810. It has a distance of about 200 parsec, and is one of the nearest symbiotic stars and a well known jet source.[5]
By its gravitational pull, the white dwarf draws in material from the red giant and occasionally ejects some of the surplus in weird loops to form the nebula seen in the linked image.[6] The whole system appears reddened because it is situated in a very dusty region of space, and its blue light is absorbed before reaching us.
The nebula around R Aquarii is also known as Cederblad 211. According to Tom Polakis,[7] as of 1998 no one had succeeded to observe this challenging object visually. It is possible that the nebula is the remnant of a nova-like outburst, which may have been observed by Japanese astronomers, in the year 930 AD.”

I’m sure CED 211 has been observed visually many times since 1998, but it’s interesting that a comment like that would be noted in Wikipedia. Has anyone seen the fainter filaments that are perpendicular to the brighter spikes I saw?

A DSS image looks like this:
Attachment 817

The HST image – it barely looks like the same object!
Attachment 818

My sketch from last week:
Attachment 819 Attachment 820

I also came across a wonderfully detailed amateur image of CED 211 here:
http://www.baskies.com.ar/PHOTOS/R_AQUIARII.htm

“Give it a go and let us know!”

Good luck and great viewing!

Howard,

I observed R Aqr yesterday from a good (but not excellent) site with good transparency and seeing. This is an intriguing object indeed. At 150x the reddish hue was obvious as well as the nebulosity that extends roughly east-west. At magnifications of 500x, 720x and 1000x I made a puzzling experience. At first the object looked very much like in the DSS photo: symmetrical, both arms equally long, and each with a slightly brighter condensation at their ends. Also I suspected a filament to the south. However, the image changed after a while of observing. Now the object lost its symmetry as the western arm appeared longer, about twice as long as the eastern one, and the western condensation seemed to vanish. While my first impression corresponded to the DSS image, the later view was closer to your drawing and to the Hubble photo. I wonder whether the difference between my two views is the same as the discrepancy between the DSS and the Hubble photo. Do you have any idea, why the DSS and the Hubble are so different?

Greetings
Johannes

Hi Johannes,

My guess is that the HST and DSS photos look different because of exposure time and different filters used. My first impression of the nebulosity was a fairly symmetrical glow around R Aquarii and I saw only the brighter spike. After a moment using averted vision the fainter, opposite spike appeared as did the small knot off the end of the brighter spike. It's possible that sky conditions changed just enough to alter your view, but I've have found that sometimes my first impression changes fairly dramatically with continued observing.

Howard,

I have looked into some online resources, and it seems that the Hubble photo covers only the central pair of stars (the black dots) plus the innermost portion of the northern and southern jets, while the DSS photo shows the entire object including the eastern and western arms. Also, if you look at the blue POSS II plates, the western arm has a fainter extension to it that goes beyond the bright condensation. This might account for the ambiguity in my observation. As soon as the extension came into my view the western arm was doubled in length.

Greetings
Johannes

Hi Howard,

I visited the star three years ago with my 27" under nearly perfect conditions (seeing and transparency).

Both condensations were bright and had equal length with small plobs at the ends. The starting points of both condensations were a little bit shifted. The NE arm was much brighter. I could not detect the fainter SE-NW arms.

27", 586x, NELM 7m+, Seeing I
Attachment 836

Hi Howard,

this is an extraordinary object in many respects, excellent choice! It is amazing, that we can observe visually the details of this symbiotic system. This is one of my favorite objects in fall, given that transparency and seeing are good enough. I live at 48° N latitude, so R Aqr is never high above the horizon.

My observations are very similar to those of the others. At high magnification with my 22", the NE arm is curved with a bright knot at the end. The SW arm is much fainter and appears therefore less well defined. I get a somewhat better contrast with the OIII filter.

I have never succeeded to see the more extended but fainter outer E-W segments of Ced 211 (neither with H beta filter).

Have been waiting for this one since last year and viewed it last night with steady skies and acceptable transparency.
[I have edited this in early Oct 2014 as on careful re-listen to my taped observation I am sure I was only seeing the bright elongation and NOT the very dim elongations]

I agree that this is a peculiar and unique object although very tiny and as such requiring very good seeing. But then again, so is Eta CAR in that sort of class as a one of a kind tiny object.

After having brought this up in my 18" where with unfiltered view the brighter extensions off of both sides to me were clearly present on both NE and SW with averted. The direct view as well as averted offered the very rich golden-orange color that was a nice surprise in itself as I had only my chart I made a year ago with no notes taken with me last night or reviewed on this post till today when Steve Gottlieb pointed me back to this post that I had seen last year. It is indeed a tiny object and Steve brought it up in his 24" as well. This object also has the distinction of being on Steves 'DeepMap 600' selected object list of which I have observed all but one of the galaxies/clusters/nebula sort of objects but have not sought out all that many of the stars he lists there, this is well worth the view. I had not thought to use filters so maybe next month as it did not rise to meridian till rather late last night. I had not noticed the knot but did feel that the more eastern extension was easier to detect than the more western arm so perhaps that is partly due to the knot.

Hi,

I know this is a very old thread but I could observe R Aquarius under fair conditions and Bortle 1 sky (Namibia) recently. I saw a S-shaped nebula around a star. The star itself did not have any hue so far at 670x. Firstly I was confused by having observed the brighter reddish star nearby but finally I noted my mistake and observed the right star. Interestingly an UHC filter worked well showing the nebula and knots more easily at first impression. But at the end I observed the object without any filter because all details could be seen as well. BTW OIII fails. At 670x and using a 25” Dobson I could spot a bright knot at south within the “S” which lied close but outside the main arm. At its end I could spot a knot. At north the arm tends to brighten up and becoming hazily and showing a brighter knot outside. After all I checked out some pictures and in my opinion the POSS blue plate is giving the best impression of the nebula.

Oliver

9/29-30/22 R Aqr/Cederblad 211. After failing to confirm seeing anything on the 27th with the 16” at 300x (poor seeing), I was able to see the nebula on the 29th. I was expecting it to run east to west thanks to the DSS image, but I kept seeing it running northeast to southwest! The brighter section sat on the northeast side of the red star while the longer and fainter section was on the southwest. From tip to tip it was about 30” long. The nebula was still visible at 150x. On the 30th I attempted to see it in my 10”. At 260x, it was visible but very difficult. Oddly, it was slightly easier to detect the diagonal “slash” of glow at 200x! So much for Ced 211 being difficult! Here is a link to a CloudyNights post where I do my own OOTW for it.

Scott