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Cosmic Challenge: NGC 2371 - 2372
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Cosmic Challenge: NGC 2371 - 2372
February 2025
Phil Harrington
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Target |
Type |
RA |
DEC |
Constellation |
Mag |
Size |
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NGC 2371 - 2372 |
Planetary |
07h 25.6m |
+29° 29.4’ |
Gemini |
13 |
55" |
Gemini offers two intriguing planetary nebulae for stargazers: the well-known Eskimo Nebula (NGC 2392) and the lesser known but equally fascinating NGC 2371 - 2. While the Eskimo Nebula dazzles with its bright, structured halo resembling a face framed by a parka, NGC 2371 - 2372 (traditionally abbreviated NGC 2371 - 2) presents a more subtle, ghostly charm.
Many early observers mistakenly interpreted NGC 2371 - 2 as two separate objects. William Herschel, who discovered this two-faced object in 1785, described it as "two, faint of equal size, both small, within a minute [of arc] of each other; each has a seeming nucleus, and their apparent atmospheres run into each other." This led John Dreyer to list this planetary twice in his New General Catalog. Dreyer also listed M76, the Little Dumbbell in Perseus twice (NGC 650 and NGC 651) for much the same reason. Maybe we should christen NGC 2371 - 2 the "Littlest Dumbbell."
Actually, NGC 2371 - 2 already has a couple of nicknames: the Peanut Nebula for its double-lobed shape and the Double Bubble Nebula for its similarity to a piece of bubble gum still in its twisted wax paper wrapper. But to me, photos like that below that reveal faint extensions remind me of Darth Vader's TIE Advanced x1 Starfighter with its distinctively bent wing panels.
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Above: Evening star map. Credit: Map adapted from Star Watch by Phil Harrington |
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Above: Finder chart for
this month's Cosmic Challenge.
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Today, we understand that NGC 2371 - 2 is a single object with bipolar tendencies. The nebula’s estimated age is roughly 10,000 years, based on the expansion rate of its ionized gas shells. The angled view that we have of the planetary from Earth shows two bright lobes connected by a faint, equatorial ring. The lobes are composed of ionized hydrogen, oxygen, and nitrogen, giving the nebula a greenish-blue hue in optical images. Surrounding the main structure is a faint halo, remnants of earlier mass-loss episodes. Its central star, the incredibly hot remnant of a red giant, has a surface temperature estimated at 240,000° Fahrenheit. This star is in the final stages of its evolution, transitioning to become a white dwarf. It shines at 18th magnitude and likely only visible in the largest backyard telescopes.
Although I have read reports of it being seen through telescopes half the size, NGC 2371 - 2 always proves troublesome through my 8-inch (20-cm) scope from my suburban backyard. Observers with 3- to 5-inch (7.6- to 12.7-cm) telescopes might want to give it a go from dark (Bortle 1-3) skies.
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Above: NGC 2371 - 72 as taken by the author using a 6-inch (152mm) f/2.2 Celestron Origin Home Observatory. Details can be found on my Astrobin posting. |
The nebula spans roughly 1.4 arcminutes across, which corresponds to a physical size of about 1.5 light-years. Its small apparent size also means that, once it is spotted, NGC 2371 - 2 is best seen at higher magnifications. By cranking up to at least 150x, and by using averted vision, the nebula's disk appears to have been severed in two (see my digitized sketch below). The two lobes are oriented northeast-southwest. The southwestern lobe (cataloged separately as NGC 2371) impresses me as slightly brighter than the other (NGC 2372).
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Above: NGC 2371 - 2 as seen through the author's 8-inch (20-cm) f/7 Newtonian at 158x.
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Good luck with this month's Cosmic Challenge! And be sure to post your results in this column's discussion forum.
Until next month, remember that half of the fun is the thrill of the chase. Game on!
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About
the Author: |
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Phil Harrington's Cosmic Challenge is copyright 2025 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. |
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- Jon Isaacs, John O'Hara, warddl and 1 other like this
8 Comments
Last night was unseasonably warm with clear skies so I gave this a try. I piggybacked a 5" SCT on a 16" GOTO SCT. With a magnification of 100x in each telescope, I used nearby NGC 2392 to determine the alignment of the 5" relative to the 16". Moving on to NGC 2371-2, it was easily visible in the 16" but not immediately seen in the 5".
When attempting observations of difficult objects, I follow the quip from Lone Watie in the movie “The Outlaw Josey Wales” to “endeavor to persevere”. After noting the location of NGC 2371-2 in the 16" relative to stars visible in the 5", and blocking out all extraneous light, I was able to see a faint smudge with averted vision after several minutes of peering in the 5".
I had high expectations that using a UHC filter would help. While the smudge of NGC 2371-2 was still visible in the 5", field stars were dimmed down so much that it was difficult for me to stay oriented (background skyglow was also dimmed to the extent that it took a little effort to make sure my eye was correctly positioned to see the total field of view). I believe I was better dark adapted at this point since, after removing the filter, NGC 2371-2 was easier than it had been previously. Perseverance paid off!
In the 16" with a UHC-type filter, the view of NGC2371-2 was enhanced while still having enough aperture to see the brighter field stars. The best view was at 200x, with 400x being too much magnification. The difference in brightness of the two lobes was notable.
Phil:
Again I must say I enjoy your cosmic challenges. There are three basic classes:
- I know this one well. This has two subcategories, I know the numbers or I have to look it it.
- That looks doable, I'll put it on my list
- No way Jose.. I'm not seeing that even with the 22 inch under 21.3 mpsas skies. Maybe if I get cataract surgery.
NGC 2371-2372 is one of my favorites, one that I've observed many times many scopes. It is doable from bright urban skies (18.2-18.6 mpsas) in my 10 inch F/5 with an O-lll filter.
For star hopping I use a 4 star asterism consisting of two pairs at right angles with one pair pointing almost directly at NGC-2471-72.
Well this is a very strange coincidence. I started trying to image NGC 2371 on 1-20-25. The image was not good so I kept trying on the next clear night, 1-30-25. Still didn't look right. So I tried again last night. But first I went to Cloudy Nights and searched for NGC 2371 hoping to see how others imaged it. And there it was as the February Cosmic Challenge! Here's nine hours of five minute exposures with an 8 EdgeHD, .7 Celestron reducer, ASI533MC Pro and a UV/IR filter from last night. Thanks Phil!
great color!
It's been quite a few years since I've observed NGC 2371-2 last time, so of course I had to give it a shot. Yesterday evening, I was out with my Zeiss Meniscas 150/2250 taking a picture of it, while I observed it visually with a 6" f/8 Meade Starfinder Dobsonian. Both from the Bortle 3 backyard at my parent's farmhouse.
Starhopping to the planetary is fairly straightforward, using the asterisms Jon outlines in his post above. I simply aimed the finderscope at approximately the right spot, and the planetary was visible as a little smudge in the 6" at 51x (24mm ES68). The double lobe nature was visible at once. Increasing the magnification to 87x (14mm ES82) and 111x (11mm ES82) brought considerable more detail into view. Now the two lobes were quite different, with one being much brighter than the other, and having a nearly stellar core, that isn't quite centered in the lobe. The central star wasn't visible.
The photo turned out so-so. I had some difficulties with the flats, so I had to crop the image a fair bit, to mask off the ugliest parts. I also had to throw away a lot of frames, due to trailing from gusts of wind. Here's the result:
NGC 2371-2, February 18th, 2025. Zeiss Meniscas 150/2250, 40mm ES52. 23x30 seconds at 6400ISO. OnePlus Nord CE3 Lite, Deep Sky Camera app. Stacked in DSS, edited in Windows Pictures. Cropped version, due to poor flats. Many frames had to be thrown away, due to wind.
Clear skies!
Thomas, Denmark
Reading Thomas's post yesterday, it reminded me to give NGC-2371-72 a try this evening. Thomas was attacking it from dark skies with a 6 inch. I was attacking from bright skies with my 13.1 inch Starsplitter and an O-lll filter.. The skies measured 18.1 mpsas overhead, 17.8 in in the area of interest.
I was able to see it as two fuzzy spots at 150x..
Jon
Here's an AI denoised Seestar S50 image of NGC 2371-2 (the Double Bubble Nebula) that I captured last night from the orange zone Naylor Observatory.
I also observed NGC 2371-2 using the observatory's 17" f/15 classical Cassegrain at 170, 259, and 324x.
Attached Thumbnails
I cropped and resized the above image of NGC 2371-2.
Attached Thumbnails