Another nearly perfect circle in space!

By Phil Plait | August 4, 2011 7:03 am

Hard on the heels of my post on Abell 39 last week comes another nebula that forms perhaps an even more perfect circle: PN G75.5+1.7, aka the Soap Bubble Nebula:

[Click to ennebulenate.]

That’s really cool. As I pointed out in the earlier post, these are called planetary nebulae, and are the results of the dying stars blowing off winds of gas. They are very rarely circular, instead coming in all kinds of fantastic shapes. It’s thought that you might not get a PN unless the star is binary or swells up to eat its planets as it dies; when that happens the star can get spun up and eject the gas more easily.

It’s not really a circle, of course: it’s a sphere, or more properly a spherical shell. It really is like a soap bubble! The bright edge is due to an effect called limb brightening, which I explained in that earlier post.

This isn’t really well understood, but to get one this symmetric the star must be a loner, and spherical ones are pretty rare. The Soap Bubble is extremely round, maybe even more than Abell 39, so that in itself is interesting. It’s also located near to a vast complex of gas and dust, which is weird: I’d expect the surrounding material to mess up the nice, neat, spherical structure of this nebula. Most likely the Soap Bubble is actually between us and the complex, in relatively empty space.

Also nifty is that this object was discovered by an "amateur", Dave Jurasevich. I know Dave; he works at Mt. Wilson in California and helped us run the 100" Hooker telescope when we were filming Bad Universe. He’s a good guy, and discovered the Soap Bubble in 2008 while photographing the sky in the constellation Cygnus. It’s a good story, which he recounts on his site.

The picture above is from the 4 meter Mayall telescope at Kitt Peak, taken by Travis Rector (his name may be familiar; I’ve posted stuff by him before). He used two filters: one picks out light from warm hydrogen (colored orange in the picture) and another that selects oxygen (colored blue). Planetary nebulae strongly emit at that latter wavelength — it’s not that they have more oxygen, it’s that oxygen is a very vigorous producer of light in thin gas — so it looks blue in this photo.

In the comments of my Abell 39 post are links to even more pictures of nearly circular planetaries. If I had known about all these a few years back when I was working on Hubble, I would’ve applied for time to observe them. A spectrum of these guys might reveal a lot more about them, and give us a clue as to why they are so nearly perfect. It would tell us if they are expanding evenly in all directions, for example, and maybe the density of the material around them.

I wonder how many of these exist? I’ve never seen a catalog of them. It would be interesting to know more about them, like position in the sky, age, and so on. Someday, our own Sun will expand into a red giant. If it swallows Mercury and Venus, as we expect it will, it might be a planetary nebula too. I wonder what it will look like, 6+ billion years from now…?

Tip o’ the [OIII] filter to Astron/JIVE. Credit: T. A. Rector/University of Alaska Anchorage, H. Schweiker/WIYN and NOAO/AURA/NSF.

Related posts:

A nearly perfect circle in space
A glowing bubbly bauble in space
The knotty Cat’s Eye halo
A delicately violent celestial shell game

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (24)

  1. Chief

    Now this one looks like its from Explorers.

    I wonder if more would be located above and below the disks of galaxies and less around the rims.

  2. Grand Lunar

    I wonder if this will be the Sun’s appearence when it enters the planetary nebula phase.
    Although I bet that the giant planets might fudge it up a bit.

    Anyway, keep ’em coming Phil! These are great!

  3. SkyGazer

    Space is full off beauty!
    Maybe it´s the work of an Intelligent Smoker.

    And off topic.

    Want a laugh?
    See this:

  4. Joel

    So what is the big patch of nebulosity in the background?

  5. Bob Finn

    So if you had studied these when you were working on Hubble, would they be called “Hubble Bubbles?”

  6. QuietDesperation

    Is there spectrographic confirmation that it is, in fact, soap?

    OMG, it’s Space Scrubbing Bubbles! They travel from planet to planet, cleaning and sterilizing the surfaces!

    Intelligent Smoker.


    Oh dear, did I insult the smokers in the audience?

    I should post an appropriate pony pictu- … ah, the hell with ya.

    would they be called “Hubble Bubbles?”

    Hey! Science is serious!

    It’s a real fumble to mumble silly rubble like “Hubble Bubble”. Science’s foundations would stumble and begin to crumble as people grumble about your hubble bubble, and the resulting jumble would be double trouble.

  7. SkyGazer

    @Oh dear, did I insult the smokers in the audience?
    Nah, just the morons, but they are offended by everything.

  8. Bob Finn
  9. Sam H

    @ 1 Chief: I can see that myself!! That was a cheesy but very enjoyable movie :)
    @6 Quiet Desperation: WIN.

    It’d be nice to know how big this thing is – so far as I can see there’s no star centred exactly in the middle (although the brighter top-left member of that tiny triangle in the middle seems the most likely candidate). And also – why must the sun swallow planets in order to form a planetary nebula? Wouldn’t that happen regardless?

  10. Thomas

    Someone forgot to use their coaster.

  11. SkyGazer

    @Phill Plait for your info:
    NASA to launch Lego figurines to Jupiter.
    Jupiter, his wife Juno and Gallileo!

  12. Whomever1

    Enough about this crap–start talking about the liquid water flows on Mars! Whoot! Whoot! Whoot! NASA’s tv broadcast was amazing.
    I do wonder one thing about big objects like this–or even more so on a galaxy sized object. Does it make any difference to the analysis of a galaxy (seen millions of light years away) that the nearer edge is about 100,000 years younger than the farther edge? Or is that such a trivial moment in time on these scales that it doesn’t matter. I’m imagining the bubble here if we modeled it in 3D would look flattened in back, and pointed towards us.

  13. MarkW

    How big is the nebula? Is is a few AU? A few LY? Anyone?

  14. dave cortesi

    Was listening to a SciFri discussion of Voyager 1 locating the heliopause and it occurs to me: is not the Heliopause the exact same phenomenon as a planetary nebula? Only, of course, much more tenuous?

    Or to put it another way, is a planetary nebula just the heliopause (stellopause?) of a star whose solar wind (stellar wind?) is just a heckuva lot stronger than Sol’s?

  15. Silent Bob
  16. Smitty

    @ Chief:

    I second that. Totally looks like the Explorers force bubble.
    Strangely enough despite seeing other SciFi flicks before that one, It was seeing Explorers as a kid that really got me thinking about space, what’s out there and how to get there.

    Oh and hey, what’s that in the bottom left of the bubble? Is that a Proplyd?

  17. QuietDesperation

    Yes, and as a result Einstein never accepted quantum mechanics.

  18. Silent Bob



    “God does not play dice like pipes”.

  19. Anchor

    Now THAT is a photogenic setting in Cygnus.

  20. Bob

    That’s not a moon!

  21. @6 QuietDesperation, you’re trying a little too hard man

  22. cynthia

    Ooooo i love bubbles!

  23. The nebula in the background? The Milky Way goes through Cygnus.

  24. Aidan

    The dark patches are lack of gas/dust I guess, but that one in the lower left of the circle is SO round. Must be awfully tempting to over interpret features like that.


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