The Egg Nebula – CRL 2688

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An Egg nebula? Yes a very impressive Bipolar Planetary nebula located in the Cygnus constellation. I decided to hunt this down when I was not able to see much and I was looking for the exotic to photograph and challenge myself with.  I was captivated by the following Hubble image

Egg Nebula (CRL 2688)
Egg Nebula (CRL 2688) Image credit :Image credit: NASA, W. Sparks (STScI) and R. Sahai (JPL)

When I saw this I just had to see if I could get an image myself. it’s one thing to see it in textbooks, but another to see it with your own eyes and capture your own photo.

While trying to find out information on this I couldn’t find much if anything at all. most descriptions were very very short. So like always let’s get a bit of information about what we are seeing.

Egg? Why an Egg?

It is notable by it’s characteristic appearance. From what I was able to gather the Egg nebula get’s the “egg” name from the visible “shells” which are visible. [1] The material of the planetary nebula (PN) has a velocity that has been measured at 19.7 ± 0.3 km s-1 , while the mass ejection rate is inferred to be about 1.3 × 10-4 M&sun; yr-1 [2] The nebula has a patch which is obscuring a bit of the view. This obscured area is most likely dust [3] It is possible the particles are large graphite particles. [4] the last notable feature is the two tailing angles of light directly opposite of each other. They appear to be jets which are in an unknown state of activity, meaning they could or could not longer be active.

What are these shells and what does this mean? Well, as we talked about before a Planetary nebula is formed when a star of lower mass, much like our beloved Sun, will do. It ends the end of it’s life and as it burns out of fuel and can no longer sustain the pressures that require it to continue the process of fusion, it sputters and casts off layers of its atmosphere and mater into the void. here we see a young Planetary nebula in it’s infancy as it is being born. . .relatively cosmically speaking. In my previous photos of Planetaries, or one of my firsts, the Ghost of Jupiter, or The Cat’s Eye or the Saturn Nebula, the gas has been cast off in those and it has expanded quite some distance.

This star is in the preplanitary nebula stages. You are seeing a PN being born. one thing that made this interesting is this quote by NASA:  “Light vibrating in the plane defined by each dust grain, the central star and the observer is preferentially reflected, causing an effect known as polarization” [5] The Egg is also a reflection nebula which means that the gas in the nebula is not substantially ionized, its temperature is low, and dynamical effects due to pressure gradients can be ignored.

If you want to read up on two very detailed reports on this I am goign to link 2 very detailed papers on this object. They go into great depth and so far I have not been able to find much other than a few photos with regurgitated information. The two articles are well worth a read and can be found here: The Astrophysical Journal, 492:L163–L167, 1998 January 10 q 1998. The American Astronomical Society  and THE ASTROPHYSICAL JOURNAL, 487:809–817, 1997 October 1, 1997. The American Astronomical Society.

That’s nice but what did you see?

eggfinal
The Egg Nebula I took this shot after 2 nights of searching on 9-6-2013

I was proud of the 6SE in capturing this. when you are looking with your eyes the central star in this photo is the size of  small star and a portion of the others I could not see with my eyes. I only was certain after I Left the shutter open. for a good length of time, I don’t remember the actual setting I had just started to make notes and I wasn’t sure exactly what I needed to take down. For the capturing camera I used my Orion StarShoot Deep Space Video Camera II.  Again, I am not advocating the purchase of a product, I am linking to make it easier for you to look up the equipment if you do not know what I am referring to.

Sold! Now how do I locate it?

So you want to hunt the egg yourself? This is the fun part. Search the web and you find very very little on how to find it. In my search I found this article by Doug Scobel “Doug’s Deep Sky Challenge—An Egg Hunt in Cygnus.[6] While I want to give you direction he covers it pretty clearly. I did email him with my photo and added one suggestion to make it a bit easier.

See I had a bit of difficulty in star hoping. I am always getting turned around in my head while trying to navigate while using my scope .  . . it is because I am using a prism. so You flip the image by using a reflection of the inverse. . . what really helped was the following steps. If you use a prism like I do I took the image of the photo on Doug’s page :

dscobel.38c
Sky map Image by : Doug Scobel

What I figured to do is to take sky maps and put the image into photo shop. . .then flip or rotate them as needed depending on what gear I am doing. . . . A screen shot of the Celestron 6SE instruction manual[7]

6se image rotation
Image rotation on the Celstron 6&8 SE telescopes depending on the Equipment you use. Image is from the Celstron instruction manual provided with telescope purchase.

So from this while using the Prism diagonal, and keep in mind you can do this with ANY Star chart to help star hop. it makes it like following a map. .

flippeddscobel.38c
Same image just plugged the original into MS paint and click rotate, then flip horizontal

Now we are starting to get some where if you are like me and are bad at star hoping. In the guide he mentioned here “Near the center of the field you should be able to easily find the double star Yale BSC 8051 (BSC = Bright Star Catalog), whose components are separated by about 1.2 arc-minutes and are of magnitudes 6.0 and 8.7. Chart 1 shows where to put the Telrad circle.“ [6]  what will help you find this and get you in the ball park is the SAO number of that double is 70794, I had to refer to the SIMBAD database to find it. It was a pain because the program called stellarium (Think that’s the spelling) only had the HIP number of 103734. With this you should be able to find it. In the Celestron mount you can go to the star by using that SAO 70794, the Celestron mount does not know what that BSC# is, so to save the leg work and a few days looking , SAO 70794 = Yale BSC 8051that is the star labeled in Doug’s trapezoid. When you find this, like I did you have an easy shot using the map, as I edited it. the SIMBAD entry for the Egg is here.

Statsistics & Data:

Now that you know a bit more about it and how to find it. what are some bits of information on it?

the Egg Nebula
Observation data: J2000 epoch
Right ascension 21h 02m 18.75s[1]
Declination +36° 41′ 37.8″[1]
Distance approx[8] 3000 ly   (920 pc)
Apparent magnitude (V) 14.0[8]
Apparent dimensions (V) 30″ × 15″
Constellation Cygnus
Physical characteristics
Radius 0.2[8] ly
Absolute magnitude (V) 4.2[8]
Mass 1.8 solar Masses[9]
Temperature 6,200°C (central star)[9]                    -123°C (cloud) [9]

Size: 0.6 light year diameter
Mass: 1.8 solar masses
Temperature: 6,200°C (central star)
-123°C (cloud)

References:

  1. Sahai, R., & Trauger, J. T. 1996, S&T, 91(5), 12
  2. Knapp, G. R., & Morris, M. 1985, ApJ, 292, 640
  3.  Latter, W. B., Hora, J. L., Kelly, D. M., Deutsch, L. K., & Maloney, P. R. 1993, AJ, 106, 260
  4. Amos harpax, Saul Rappaport, and Noam Soker (22 January 2014). “The Rings around the Egg Nebula“. THE ASTROPHYSICAL JOURNAL, 487:809–817, 1997 October 1
    1997.http://iopscience.iop.org/article/10.1086/Retrieved 11 December 2015.
  5. The Egg Nebula; March 23, 2008; Nasa
  6. Doug Scobel “Doug’s Deep Sky Challenge—An Egg Hunt in Cygnus.”http://www.umich.edu/~lowbrows/reflections/2012/dscobel.38.html Retrieved 11 December 2015.
  7. Celestron (2006). “Celestron Nexstar 6se & 8se Instruction manual”PDF: www.ou.edu/lunarsooners/index/…/orange.pdf
  8. “SIMBAD Astronomical Database”. Results for Egg Nebula. Retrieved 2007-01-05.
  9. Center for Magnetic Self Organization in Laboratory and Astrophysical Plasmas (2006-09-07). “The Egg Nebula.” http://www.cmso.info/eggneb Retrieved 11 December 2015.

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