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Cosmic Challenge: Jonckheere 900


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Cosmic Challenge:

Jonckheere 900

March 2017

Phil Harrington

This month's suggested aperture range:

Giant Binoculars

 

3- to 5-inch (75-127) telescopes

 

Target

Type

RA

DEC

Constellation

Magnitude

Size

Jonckheere 900

Planetary nebula

06 26.0

+17 47.4

Gemini

12.4p

9.0"

 

Few amateur astronomers are familiar with the name Robert Jonckheere. Jonckheere was a French double-star observer who conducted research at a number of observatories over his six-decade career, including the Strasbourg Observatory in France, the Royal Greenwich Observatory in England, as well as McDonald Observatory in Texas. His life's work culminated with the 1962 publication of his General Catalogue of 3,350 Double Stars, an expansion of his earlier Catalog and Measures of Double Stars discovered visually from 1905 to 1916 within 105° of the North Pole and under 5" Separation.

 

Above: Winter star map showing the location of this month's Cosmic Challenge.

Credit: Map adapted from Star Watch by Phil Harrington

 

Above: Finder chart for this month's Cosmic Challenge.  

Credit: Chart adapted from Cosmic Challenge by Phil Harrington
Click on the chart to open a printable PDF version in a new window

Of those 3,350 double stars, the one listed here is particularly unique. In 1912 using a 13-inch refractor at the University of Lille's observatory in France, Jonckheere discovered a vague, blurry pairing embedded in a planetary nebula. Jonckheere announced his discovery the following year in Astronomische Nachrichten (volume 194, page 47) and included it as entry number 900 in his catalog.

 

Strangely, subsequent observations by Edward Emerson Barnard through the 40-inch refractor at Yerkes Observatory in 1913 and 1915 turned up the planetary, but showed no sign of the embedded binary star. Barnard described the planetary as "a brightish, ill defined, bluish white disc, possibly a little brighter in the preceding partthere is no central condensation and no trace of the central double star" (Astronomical Journal, vol. 30, issue 719, p. 208-208; 1917). That's odd, since Jonckheere, a seasoned observer, clearly described seeing two stars within the nebula. How could he make such an error?

 

Jonckheere's planetary nebula, abbreviated as J 900 in most references, lies within the constellation Gemini and is bright enough to be visible through 4-inch telescopes aimed its way. Zeroing in on J 900 is a simple task thanks to its prominent location near the feet of the Gemini twins. Beginning at Alhena [Gamma (γ) Geminorum], hop northwestward to 23 Gem and then onward to 20 Gem, both shining at 7th magnitude. Continue due west to an asterism of 8th-magnitude stars in the shape of an upside-down kite, flying half a degree west of 20 Gem, and then onward another 45' westward to a rhombus of 9th-magnitude suns. J 900 is found 10' west of those four stars. An unrelated 12.5-magnitude star lies just 11" southwest of J 900, which at first blush looks like a wide double star. This illusion was not what Jonckheere reported in his discovery announcement, however.

 

The biggest challenge posed by J 900 is not from how dim it is, but rather, by how small it is. Through my 4-inch refractor at 40x, J 900 disguises itself very effectively as just another faint star, only revealing itself when flashed with a narrowband or oxygen-III filter. A magnification of 200x hints that J 900 has a tiny disc, although distinguishing an exact shape is impossible. The central star, at 16th magnitude, is also well below our detection threshold.

 

Above: J 900 as sketched through the author's 4-inch refractor.

 

So, what exactly did Jonckheere see? Barnard's report provides an important clue. In his description, Barnard noted that the nebula appears irregularly illuminated. When viewed through large telescopes, J 900 displays an oddly rectangular shape accented by two opposing bright lobes, one to the west and one to the east. In all likelihood, that is what Jonckheere saw. He simply misinterpreted the two brighter regions as a double star.

 

Have a favorite challenge object of your own?  I'd love to hear about it, as well as how you did with this month's test.  Contact me through my web site or post to this month's discussion forum.

 

Until next month, remember that half of the fun is the thrill of the chase.  Game on!



About the Author:

Phil Harrington writes the monthly Binocular Universe column in Astronomy magazine and is the author of 9 books on astronomy.  Visit his web site at www.philharrington.net to learn more.

Phil Harrington's Cosmic Challenge is copyright 2017 by Philip S. Harrington.  All rights reserved.  No reproduction, in whole or in part, beyond single copies for use by an individual, is permitted without written permission of the copyright holder.

 


  • SaberScorpX, okiestarman56 and oalithgow like this


9 Comments

I wasn't aware of this one.  Looks like a challenge for the local poor seeing in large aperture.  I will give it a try this coming month conditions permitting. 

    • PhilH likes this

I'm new to the Cosmic Challenge...sorry to say I hadn't hit upon it previously.  This month's object, J 900, caught my attention.  Two weeks ago I began observing a list of about 600 planetary nebulae visible from my latitude (derived from the SAC database with some data filters).  I observed J 900 on February 24 from my somewhat light-polluted location at the edge of the Las Vegas valley.  My "planetary nebula" scope for this non-dark-sky location is a Meade 16" LX200 classic.

 

Through the 16", at 150x J 900 was visible and revealed its emission line nature when flashed with a narrowband filter as you note.  At 400x, it presented a small disk.  Without a filter at 400x, it still showed up and was a pleasing small object next to the 12.5 mag. star you noted.  This is definitely an object that can be seen well under less than dark skies.  In fact, it probably won't look that much better under a dark sky since the high magnification needed to see it spreads out the background skyglow.

 

Just a couple notes that made things easier:

 

- For objects NOT in the LX database, the RA and Dec should be precessed to 2017.  As I discovered my first night out entering RA and Dec manually, using J2000 coordinates will result in a significant error (for the 16", about half the FOV in my lowest power eyepiece).  Using precessed coordinates to the current year results in much better pointing accuracy.

 

-I downloaded 30 min x 30 min POSS2 red images (and mirror-reversed them for the SCT) for use as finder charts. 

 

Jay

    • PhilH likes this

Also as:PK194+02.1 and in SIMBAD its PN VV 28

listed as J900 in Burnham's Vol 2 on p 911 as " vS, B, mag 12. diam 10"; nearly stellar."

It's also part of the AL Pn observing program. I remember observing it years ago. I'll give it a try again later this month.
Photo
Dave Mitsky
Mar 07 2017 10:22 PM

I learned about J900 from an article in Astronomy back in the 1990s and have observed it a number of times since then. 

 

https://futurism.com...jonckheere-900/

 

I've also seen J320 in Orion. 

 

http://www.pbase.com...image/150620355

Only recently found this articles....really loving them. It reminds me of the SmallWonders by Tom.

And now that i have a deacent telescope and hercules is on the horizon, guess i will start this challengues with the 1st one "Gallaxies around M13"

 

Thanks a lot for thaking the time to write this articles Phil.

Got it tonight despite the overbearing moon.  With the moon and in town I used the 10" f/5.  Seeing was  probably 3/10 for the 10" at the time.  Transparency was good. 

 

At 114x it was non stellar, but uncertain.  At 250x it was clearly a non-stellar fuzzy patch with a star a few arc seconds away to the south.  A Farpoint UHC made the patch stand out more and the star faded.  I didn't try to analyze the shape further due to the seeing and moon.

 

In the original Uranometria set it is plotted under PK 194+2.1 as mentioned above.

    • PhilH likes this

Got it tonight despite the overbearing moon.  With the moon and in town I used the 10" f/5.  Seeing was  probably 3/10 for the 10" at the time.  Transparency was good. 

 

At 114x it was non stellar, but uncertain.  At 250x it was clearly a non-stellar fuzzy patch with a star a few arc seconds away to the south.  A Farpoint UHC made the patch stand out more and the star faded.  I didn't try to analyze the shape further due to the seeing and moon.

 

In the original Uranometria set it is plotted under PK 194+2.1 as mentioned above.

Nice job, especially with that Moon so nearby!  waytogo.gif

My first observation of J 900 was over 35 years ago with a C-8.  I'm sure I took a look since it was listed in Burnham's or perhaps plotted on Becvar's Atlas of the Heavens.

 

8" (12/21/81): At 100x, fairly faint, stellar. Used 250-333x to confirm disc.  Seemed slightly elongated at high power with a 13th magnitude star just south. Takes high power well.

 

A few years later I also observed it with my 13" Odyssey I and noted a bluish color.

 

13" (1/11/86): at 144x appears moderately bright and very small but definitely non-stellar.  Takes high power well and an obvious disk is seen at 214x.  A mag 13 star is just off the south edge [11" from the center].  The disc is quite prominent at 535x, slightly elongated NW-SE with a bluish tinge.

 

With my 17.5" I noted a "brighter central spot", though I don't know if I was glimpsing the CS or the brighter lobe.

 

17.5" (12/28/00): At 280x appears a bright, compact, high surface brightness disc, ~8" in diameter with a bluish color.  Forms a close double with a mag 13 star off the south edge.  At 380x, the planetary was slightly elongated and a brighter central spot was highly suspected several times.

 

Steve



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