Object of the Week February 24, 2013--- NGC 2163

[Howard B]

NGC 2163 = Cederblad 63

Orion

RA
06 07 49.5

DEC
+18 39 27

MAG 11 for the central star, EM* LkHA 208

Type: Bi-Polar Reflection Nebula

Discovered by Edouard Stephan in 1874 using the 31.5 inch Foucault reflector at the Marseille Observatory, NGC 2163 went missing because Dreyer copied Stephan’s declination measurement incorrectly in the first edition of the New General Catalog. For more about the history of how this fascinating object was lost and found again, check out The NGC/IC Project at http://www.ngcicproject.org/ or O’Meara’s Hidden Treasures, pages 174-177.

2163 is a beautiful example of a bi-polar reflection nebula showing two opposing outflows, with the northern flow being the brighter of the two. Notes from my first observation from April 1, 2008 state:

“This bi-polar nebula is considerably fainter than I expected. One side is obviously brighter, but then that’s still pretty faint. The best view is at 253x and is slightly enhanced with the broadband filter. This is a nifty object; too bad it’s not a little brighter. 10:23pm, 21.20 SQM.” (28 inch f/4 from Chuck Dethloff’s front yard, 600 feet altitude)

My second observation from September 28, 2008 was a little better:
“A much better view of this bi-polar nebula than from Chuck’s place – the two flows are quite distinct and relatively easy to see at low power. The northern flow is brightest and most distinct though. Best view at 253x but almost as good at 408x. 4:53am, 21.95 SQM.” (28 inch f/4 from Steens Mountain, 7400 feet altitude)

No surprise, this shows how a darker, more transparent sky and altitude can improve an observation, but also that my first observation was pretty good – even though I had to work harder to see 2163 well and I didn’t benefit from using a higher magnification.

Here’s my sketch from Steens Mountain and a DSS image to compare – note there’s a lot of fainter nebulosity in the area.

N2163_sketch crop.jpg dss_N2163 crop and rotate.jpg

The pinched waist area was pronounced at both observations, which make the north and south outflows resemble an hourglass, although the nebula visually surrounds the star LkHA 208, from which the outflows originate. I haven’t tried a smaller scope on 2163 yet, although O’Meara’s sketch in Hidden Treasures shows both outflows and he used a 4 inch refractor. He notes that the nebula seems separated from the star “by a tiny spit of dust” – what do you see?

“GIVE IT A GO AND LET US KNOW”
GOOD LUCK AND GREAT VIEWING!

[Uwe Glahn]

Hi Howard,

I'm not the real "nebula guy" but this RN looks pretty cool.

I observed this nebula with 16" and noticed "bright but small RN around 11mag CS; cometary outflows to the N and S; N outflow a little bit brighter and ~1' long; S outflow half as long as N, slim with less cone structure; better defined to the W side"

16", 257x, Seeing IV, NELM 6m5+
NGC2163.jpg

[reiner]

Hi Howard,

this is a nice one! I have observed it a few times with different apertures, also as part of my observing project on Young Stellar Objects here http://www.reinervogel.net/YSO/YSO_e.html.

My notes with 22" are as follows:
Ced 62 (NGC 2163) is a bright bilobal nebula around HBC 193 at the border Orion/Gemini that is visible already in medium sized telescopes. Not precisely like an hourglas, the nebulosity is not fully constricted at the position of the star. W side is better defined. N fan is brighter and larger with a brighter streak at its W border. S fan is weaker and appears a bit separated from the star.

It was also well accessible with my 8" Dob from my suburban backyard and appears then as a diffuse elongated glow around the young star with a hint of constriction.

If I understand it correctly, we are observing here a molecular cloud that has been cleared along the rotation axis of the protoplanetary disk of the YSO, forming a kind of double cone with the star defining the tips of the cones. The light that we see is actually light being reflected from the inside of these cones. This is similar as with Hubbles Variable Nebula or PV Cephei and several other nebula of this kind.

[Jimi Lowrey]

Howard,

Nice object and great story.

I have not observed this in years. I will put it on my list for a revisit if the moon ever gets out of the way!

[Astrojensen]

I have observed this one with my 63mm Zeiss. I couldn't really see any obvious details, but there was something "funny" about the star, like it wouldn't really focus.


Clear skies!
Thomas, Denmark

[Howard B]

If I understand it correctly, we are observing here a molecular cloud that has been cleared along the rotation axis of the protoplanetary disk of the YSO, forming a kind of double cone with the star defining the tips of the cones. The light that we see is actually light being reflected from the inside of these cones. This is similar as with Hubbles Variable Nebula or PV Cephei and several other nebula of this kind.

Hi Reiner, this is good to know - I couldn't find any info pertaining specifically to the nature of 2163 other than it's a reflection nebula. Can you direct me to where you found this info? Many thanks!

[reiner]

Hi Howard,

I stumbled over that when I was scanning web and literature for my YSO project. I am not sure if that explanation is right or a misconception. I have to check whether I find it again.

[Andru]

After my observation (see below) I read Reiner's note: "S fan [...] appears a bit separated from the star." That was exactly what I had noted, too. But it doesn't match Uwe's and Howard's observations. It would be interesting to read whether a bigger telescope could confirm one of the versions?

NGC2163.jpg
14", 270x, NELM 6m5, bad seeing

[reiner]

Hi all,

there was the question about what we actually observe: a) the molecular outflow or b) the illuminated inner side of a cone cleared by the outflow in the surrounding molecular cloud. I had always thought it is the latter one, but I did not find the papers where I read this. If I recall it correctly it was from a PhD thesis or a talk by a professional published on the web.

I have also tried to contact a professional astronomer who worked on YSOs. I have also scanned several papers on that but the professionals do not appear to address this question, at least not if it comes to continuous optical emission (outflow is usually studied in emission lines). Now I found one paper that addresses this at least for PV Cephei. The paper by Boyd is here (and it is interesting anyways as it is about the recent variability (for us: visibility :-) ) of Gyulbudaghian's Nebula)

http://adsabs.harvard.edu/abs/2012SASS...31...65B

Boyd says:
"Light from PV Cephei shining on the inside of
the cavity in the surrounding molecular cloud cleared
by the northern outflow creates the variable reflection
nebulosity variously known as RNO125, GM29 or
Gyulbudaghian’s Nebula."

So Gyulbudaghian's Nebula is not exactly Ced 62, but on the other hand, it is not too different. Similar as Howard, I have not found anything in that regard for Ced 62.

As outflow, molecular cloud, jets, and associated Herbig-Haro objects are often confused, I thought it might be good if we find out what we actually observe. If anybody finds further information on this, it would be great to learn about it.

I'll keep you updated if I get a response from the professional astronomer.

PS: I found another interesting site about what we actually see for another YSO, R Mon and Hubble's Variable Nebula by Chris Brown. See here.