By Phil Plait | January 11, 2011 7:06 am

Looking at this Hubble image, you might think it’s another run-of-the-mill yet spectacular spiral galaxy, nearly edge-on, with a pretty spiral in the background. But then you let your eyes scan down to the bottom…

Hey, what the heck is that giant green thing?

That, me droogs, is Hanny’s Voorwerp. Click the image to, um, to… envoorwerpenate.

OK, you ask, what’s a Voorwerp? Well, it’s Dutch for "thing". Doesn’t help much, though, does it?

All right then, let’s back up a bit: Hanny van Arkel, who discovered it, is not an astronomer. But she was reading a blog entry by Brian May, who is the guitarist for Queen as well as an astronomer. He had written about Galaxy Zoo, a project where you can classify galaxies on your computer. Being a Queen fan, Hanny checked it out, and started looking at galaxies… which is how she found this weird green smear of light. She asked about it, and astronomers took interest… and the result is this amazing Hubble image of a very odd object.

What is it? Well, the green color is a dead giveaway that it’s a giant cloud of gas; the green comes from glowing oxygen, spread ethereally thin. The nearby galaxy must be involved, as there’s no other source of illumination, which in turn means this thing is pretty big. In fact, it’s the same size as our galaxy, 100,000 light years across!

The thinking is that there is a supermassive black hole in the center of that galaxy (which is named IC 2497). For a long time, that black hole was swallowing down material, and it turns out to have been a sloppy eater: as material falls in, it piles up in a disk outside the Final Plunge. This disk heats up, and various forces can combine to create huge jets of energy and matter that scream out in opposite directions.

At the same time, well outside the galaxy, there is a stream of gaseous material hundreds of thousands of light years long that was basically minding its own business. Then one of these beams of energy from the center of IC 2497 slammed into it, lighting it up and making it glow like a neon sign.

But there’s also matter in those beams, and that has apparently compressed the tip of the Voorwerp on the side facing the galaxy (facing upwind, if you like). In the image, you can see how the tip is yellow; that light is coming from stars that are forming as the gas is compressed. These stars are being born well outside the galaxy itself! What a view any potential future civilizations will have: an almost entirely black sky, with a giant galaxy hanging there looking down on them. They’ll have interesting mythology, I’d wager.

Anyway, at some point, maybe 200,000 years ago, the material going into the black hole at the heart of IC 2497 choked off. Maybe the material just ran out, the last of it falling into the hole. When that happened, the searchlight beams shut off. The Voorwerp is still glowing, because it takes thin gas a long time to lose its glow, but eventually it’ll stop glowing too.

When I first saw the image, I thought the Voorwerp was cone-shaped, like a megaphone pointed a bit away from us. That circular hole was what gave that impression, but my old friend Bill Keel, an astronomer involved with this observation, speculates it may be a shadow of some object near the black hole, like "a fly on a projector". There’s material there, but we don’t see it lit up because it’s in a shadow. Bill thinks this may be the case because there’s no other obvious way to create a big hole like this in the material itself; an explosion or wind from a star would have to be titanic to create such a hole, and there’s no apparent streamers or filaments you’d expect to see.

Scientifically, this is a fantastic object. Nothing like this has been seen before, so everything we learn about it is new. But the other story is equally wonderful. I’ve shown a picture of Hanny here, because I want you to see that she is what is known in the über-geek world as "a normal person". She’s a school teacher, and liked music, specifically Queen (a woman of excellent taste). Because she liked Brian May, and Brian wrote about Galaxy Zoo, she discovered this object. You can read about it in her own words on her website, in fact.

The thing is, she liked science. She wasn’t an astronomer beforehand — I suspect she has a pretty good grasp of it now! — but decided to try her hand at identifying galaxies. And now she’s deservedy famous; she discovered something no one had ever seen before, and even with Hubble observations still leaves quite a bit to be understood.

I love citizen science projects like Galaxy Zoo and its offshoots. It doesn’t always take a degree, or years of training, to make an impact of science.

All it takes is interest. That can lead to love, and a degree, and training… or just to more interest. But clearly, that can be enough.

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (60)

  1. Mapnut

    Yahoo News is right on top of this story, with a reasonably good article. I was tentatively annoyed that they just called it a “blob” – why didn’t they call it a nebula, says I? But then nebulas aren’t usually 100,000 light years wide. Even Phil only manages to come up with “thing” and “smear”.

    The article said that the stars being formed are less than 2 million years old. An astute commenter pointed out that if the Voorwerp is 650 million light years away, the stars are really 652 million years old.

    Who will discover the next Voorwerp?

  2. Sam H

    This is amazing! If that nebula is the diameter of our whole freaking GALAXY, then that must be the largest known nebula in the universe! And it ain’t pink like usual – IT’S GREEN!! So amazing how the universe can destroy our expectations! Just imagine what’s out there :D!!!

    The main citizen science project I currently have an interest in is PlanetHunters. The only problem is that identifying a planet’s light curve is tricky. How many dips does it take? How deep should it be? What I need them to do is show the light-curves of known Kepler planets, so we can know what new ones will look like.

  3. Oli

    How do we know there isn’t a giganormous gas cloud around the entire galaxy, just not illuminated by the black hole?

  4. chris j.

    if the voorwerp truly is extragalactic, then the biggest question on my mind is how a 100k l.y. cloud of oxygen could have formed in the first place. true intergalactic gas should be about 75% H and 25% He. looking more closely at it, the lumpiness superficially resembles structures we regularly see in gas and dust clouds in the milky way. the fact that there is no visible source for illumination does not mean that there isn’t one, and finding it can be tricky.

  5. Messier Tidy Upper

    Great story and image. Thanks BA & my congratulations and well done to Hanny. :-)

    Looking at this Hubble image, you might think it’s another run-of-the-mill yet spectacular spiral galaxy, nearly edge-on, with a pretty spiral in the background.

    Do you mean background or foreground? 😉

    It looks to me as though there’s one prominent tilted spiral (barred spiral actually? I think?) in the centre there & then a much smaller (satellite? background?) edge on spiral centre right below it but above Hanny’s Voorwerp – plus a lot more fainter background galaxies to the top left and across the bottom below Hanny’s Voorwerp as well. :-)


    PS. @ kuhnigget, just letting you know that I haven’t forgotten the religion discussion on that other older thread from a few days ago – I’ll get back to you with a response to your comment on that later today (screen time) / tomorrow in my timezone. I really must get more sleep than I’ve been getting lately. Apologies about the delay.

  6. Brian

    I still prefer my name for it: The Great Green van Arkel Seizure

  7. Ron1

    “envoorwerpenate” – to enthingenize, another enplaitenized word.

  8. Edd

    Oli: Actually we do know that. In http://arxiv.org/abs/0905.1851 we show much more neutral hydrogen extending beyond the illuminated part of the Voorwerp. If you take a look at the PDF on that page you can see diagrams showing the radio emission measured in the area.

  9. Gary Ansorge

    Wow! A giant frog getting ready to ingest its prey.

    Great pics.

    Gary 7

  10. Josh

    Is it just me who thinks that a Voorwerp sounds like something out of a Douglas Adams novel?

  11. But what the heck is that below and to the left of the Voorwerp? That thing with the two evil slanty eyes staring right at us! Galaxies? Hah! It’s the evil Dark One™ of intergalactic space, and the Voorwerp is actually his shiny green cape!

  12. Bad Wolf

    In an amazing example of coincidence I was reading this entry and the comments, with the TV on in the background (tuned to MSNBC) and they were talking about the SAME THING at the same time!


    OT, this story is yet another example that smart girls are also pretty – as if we needed any more proof.

  13. This is just COOL! I wish these sort of things got more coverage in the mass media. It’s just an incredibly inspiring story.

  14. zep

    It isn’t easy being green…

  15. Joel

    thanks for clarifying Phil. I was wondering how the object might be classified. I’ve read a bit about Lyman-alpha blobs and at first thought this object might be considered in that category, but your explanation makes a good deal of sense.

    PS- i don’t think i’ve ever read you discussing LAB’s but i could be wrong?

  16. CB

    But what the heck is that below and to the left of the Voorwerp? That thing with the two evil slanty eyes staring right at us! Galaxies? Hah! It’s the evil Dark One™ of intergalactic space, and the Voorwerp is actually his shiny green cape!

    It’s not the Evil Dark One’s cape, it’s clearly his party hat!

  17. Stargazer

    New interesting object, citizen science, Brian May, yup this is a kickass story.

  18. Universe Today has a nice evolutionary diagram as to how the original cloud is a long trail from the new galaxy, based on the collision of galaxies that created it, and that the illuminated part is that part of the cloud trail that stretched under the black hole’s pole.

    There have been 17 or 18 other such voorweep’s found since, but Hanny’s was the first and by far the largest. Awesome stuff.

  19. There are several hundred (very cool) citizen science projects listed at scienceforcitizens.net. Something for everyone!

  20. GebradenKip

    Actually, “voorwerp” is Dutch voor “object”, not “thing”.

  21. Smart_Cookie

    It rather looks like a trail left by a cloaking Klingon Bird of Prey.

  22. Any idea what kind of ‘scope she used to find it?

  23. Ken ( a different Ken)

    OK, I finally got around to ordering a bunch of copies of Hanny’s comic book for my daughter’s Brownie troop. Should make a nice complement to the astronomy unit I’ll be doing with them next month. :-)

    (astrogear dot org is where said comic can be purchased – that’s Dr. Gay’s store, didn’t see it mentioned above though I’m sure you all already know).

  24. CB

    Any idea what kind of ‘scope she used to find it?

    Probably the Hubble Space Telescope, but possibly any of the scopes listed on this page: http://www.galaxyzoo.org/story

    But in any case, a big one. 😉

  25. Dave Regan

    Todd W:

    She was playing with Galaxy Zoo, a web site. So she didn’t need clear skies, didn’t have to stay up until late at night, she could just sit in her comfy chair and say “I can classify the galaxy as spiral, but what is that other thing?”.

    Up until she looked at the image, it may well have not been touched by human eyes, just automated survey telescopes.

  26. Radwaste

    CNN, decaying rapidly, has a blurb about this that just isn’t right. They called it, “300,000 miles across”.

  27. Bad Wolf:

    OT, this story is yet another example that smart girls are also pretty – as if we needed any more proof.

    And remember… “You can’t fix stupid.” :-)

  28. @Dave Regan

    Ah, yeah. Thanks. Makes more sense now. I should’ve read more closely.

  29. BJN

    Pronunciation: http://en.wiktionary.org/wiki/voorwerp

    Sounds like “four vairp”

  30. Y’know, looking at that picture, it almost looks like a particularly tall tree lit up from some off-screen light source, with a galaxy ominously dominating the sky. It’d make a good sci-fi/fantasy/horror book cover. Maybe something for a Lovecraft reprint? Very beautiful and eerie.

  31. oIo

    Yep GebradenKip (Fried Chicken? Really?), the correct translation would be “object” in stead of “thing” (which would be “ding” in Dutch).

    The pronunciation “four vairp” comes close, though the W is not really pronounced as a V but pretty much like the English one.

    Class dismissed.

    Well, at least something good came out of listening to Queen *shudder*…

    Awesome image. Looks like Cthulhu to me though.

    “Ph’nglui mglw’nafh Cthulhu R’lyeh wgah’nagl fhtagn.”
    “Ph’nglui mglw’nafh Cthulhu R’lyeh wgah’nagl fhtagn.”
    “Ph’nglui mglw’nafh Cthulhu R’lyeh wgah’nagl fhtagn.”

  32. Jamey

    I’m looking at the picture, and I noticed something kind of odd…

    At first, I thought it was JPEG artifacts, but then I looked at the original TIFF, and saw the same effect.

    Around the green glows are areas that are darker than the general background. My first thought was over-saturation of the CCD – which doesn’t usually look like that anyway, but it was just a guess. So then I looked at the area around the core of the main galaxy, which should be nicely over-saturated as well – and didn’t see any of that.

    So, is there so much nebulosity that there’s a fair bit of light-blocking going on, as well?

  33. CB

    Oh, I found later on that same page it says that the Voowerp was originally imaged from the Sloan Digital Sky Survey which uses a 2.5m telescope, and it’s that image Hanny was looking at. It was later imaged by Hubble which is the picture above.

  34. Edd

    To Dave – actually I think we know she wasn’t the first person to see it – but she was the first to *ask*. So there’s a lesson there about having an exploring and questioning mind :-)

  35. ophu

    I bet it had an unusual Genesis.

  36. Dave

    Romulan Warbird de-cloaking of the port bow!

  37. QuietDesperation

    Hey, what the heck is that giant green thing?

    If I had a nickel for every time I’ve been asked that…

  38. dre

    And just for the record, Hanny is holding a Brian May model guitar in her portrait, a replica of his famous “Red Special” that he hand-built with his father in 1963, and which he’s been playing ever since. He has licensed a couple of different manufacturers to produce the replicas over the last couple of decades.

    She must really be a fan of his. Or maybe… he’s a fan of her.

  39. It looks like an interstellar snotrocket.

  40. r0blar

    Cthulhu fhtagn! :)

  41. C’mon. Am I the only person who saw the headline, looked at the image, and said, “Gee, it does look kinda like a skeletal green TARDIS at that!”?

  42. You can see a Dragoncon 2010 panel clip here where the comic book was initially released: (starting at 4:07) The panel, held Friday, September 3rd at 10:00 PM, featured a live interview with Hanny. It was one of the most memorable Dragoncon panels for me.


  43. Gary Ansorge

    37. QuietDesperation

    “Hey, what the heck is that giant green thing?”

    Yeah, me too but mine is OLD. What’s YOUR excuse?

    Gary 7

  44. Woohoo! We made the BA blog! Edd answered some of the things I would have. As to 650 versus 652 million years – we run out of verb tenses and I think everybody gets that “now” would generally mean “at the epoch we observe for the galaxy”. Oxygen versus hydrogen – the optical spectrum shows that the gas has something like 20% of the level of heavy elements we see in the Sun. That fits if it was gas in the outer disk of a galaxy (possibly IC 2497 itself) which was pulled out by tidal forces during an interaction or merger event, the one that left its spiral arms twisted out of a flat plane. There is a lot more detail and background on the Galaxy Zoo blog (www.galaxyzooblog.org)

    Julie Frey – that was my 17-year-old watching over the Skype laptop at the DragonCon event.

    Jamey – the dark regions, I think, result from the PhotoShop polishing needed for the public-release to reduce artifacts caused by the ACS detector’s increased sensitivity to cosmic-ray damage. Just last week STScI released software to reduce those effects (it figures).

  45. Is it me or could Voorwerp be actually another word for space fart? #forever14yearsold

  46. Zucchi

    If Hanny’s Voorwerp had shown up in Star Trek, I would have thought it was another silly imaginary astronomical object they dreamed up as a plot device. Amazing universe. (And, Yea for Hanny van Arkel!)

  47. mfumbesi

    Thank you for the background story (the Queen and Brian May connection) it made for a rich and very much human tale.

  48. Peter Hook

    GebradenKip Says:

    — Actually, “voorwerp” is Dutch voor “object”, not “thing”. —

    More on GebradenKip’s comment: The Dutch word “voorwerp” is a calque on the Latinate word “object” which itself means ‘thrown’ (“-ject-“) ‘against’ or ‘in front of’ (“ob-“). The “voor-” part corresponds to “ob-” and the “-werp” part to “-ject-“. (“werpen” – ‘to throw’)

    From http://www.etymonline.com: OBJECT. late 14c., “tangible thing, something perceived or presented to the senses,” from M.L. objectum “thing put before” (the mind or sight), neut. of L. objectus, pp. of obicere “to present, oppose, cast in the way of,” from ob “against” (see ob-) + jacere “to throw”

  49. Messier Tidy Upper

    Just saw the Voorweep get a good mention on Letterman tonight (Aussie-time) too. :-)

    @12. Bad Wolf : OT, this story is yet another example that smart girls are also pretty – as if we needed any more proof.

    We don’t – & yes indeed. :-)

  50. QuietDesperation

    Yeah, me too but mine is OLD. What’s YOUR excuse?

    Gamma rays.

  51. Loc

    When I first saw the image, it reminds me of the the Gamma rays, in HULK. Wonder what kind of affect it would have on living organism?

    On a side note, a girl with brains as well as beauty, can’t go wrong with that.

  52. You can have a copy of the story in the way of a comic book here:


    I pre-ordered it some few months ago and it arrived in time. It is a great way to learn about the real story and how citizen science could be done with outstanding discoveries as reward!

  53. Anchor

    @#1 Mapnut: “The article said that the stars being formed are less than 2 million years old. An astute commenter pointed out that if the Voorwerp is 650 million light years away, the stars are really 652 million years old.”

    I get more than mildly annoyed whenever anyone ‘astutely’ points out how old things ‘really’ are because they attach a special significance to our particular distance from a particular object. The fact of the matter is we see those stars in the Vorwerp to be 2 million years old. Right now. There they are. they’re 2 million years this instant. It is utterly meaningless to think of them as ‘really 652 million years old’, not just because of the glaring assumption that the value of 650 million light-year distance is significant in its tens’ spot, let alone ones digits, but because there is absolutely nothing about our distance from the Vorwerp that should preferably set the age of those stars. Those stars can have any arbitrary age, depending on what galaxy you are viewing them from. And from the vast majority of locations available in the universe that are farther-flung than ABOUT 650 million light-years, they don’t exist at all yet, and the issue of their ‘real age’ doesn’t even arise.

    Its an old tiresome story and even many professional astronomers can’t resist the opportunity to superficially dramatize an astronomical story for popular consumption about some distant object or another, by pronouncing some object to be ‘really’ such-and-such age by adding in the utterly irrelevant light-travel time to it. It’s ridiculous and misleading and utterly inconsistent with elementary Special Relativity. Light waves or photons experience ZERO time in their journeys from WHEREVER they may come from. We see objects as they are NOW, not at some future time. Right NOW we see the Voorwerp as it IS now, not the way it will be in 650 million years. The only present moment that holds any relevance is the one we and any other observers have, not some arbitrary point in the future.

    Scale it up to the Cosmic Microwave Background, and the correct answer to the question of ‘how old’ that primordial hydrogen and helium is is ‘several hundred thousand years’, certainly not ‘13.7 billion years’. We are seeing the CMB the way it is NOW, not the way it WILL BE 13.7 billion years from now. (If it was 13.7 billion years old, it would look like our neck of the woods, not a clumpy distribution of primordial gas). To be sure, it has taken the microwave photons 13.7 nillion years to reach our PRESENT location, but that only tells us what the conditions were like WHERE we are now 13.7 billion years ago, the way it was like around here 13.7 billion years ago in OUR past. It is NOT a datum for its age. Yet we constantly see references in popular articles and books about how the CMB is 13.7 billion years OLD.

    See? Are we talking about “old”? Or are we talking about the future or the past? Confused? Its no wonder.

    The paradigm, which is a major source of this confusion in the public mind, has become so ingrained in the astro pop-culture its become difficult to even mention the peave without some sanctimonious person (often of expert rating) sneer forth with a lecture, something like, “Oh, we know that, but we all know it takes light time to reach us, so these objects really ARE that old…so lighten up, its really okay to say so.”

    Is it? Really?

    Well, in the case of the magnificent Vorwerp (=”object” in Dutch, btw), my reply would be: wake me up in 650 million years when I can ACTUALLY see those 650 million-year-old stars (actually, I’d have to stay asleep substantially longer since the Vorwerp and its host galaxy will have continued to recede as part of the expansion of the universe throughout that time, but that’s a relatively minor quibble)…but I’d be having this ghastly nightmare while asleep for the better part of a billion years about how this ridiculous paradigm continues its stranglehold on people’s wits for eon after interminable eon, outliving even the universe it contains (you know how nightmares can be sometimes) and somebody will inevitably be telling me in that far future while I enjoy gazing at 650 million-year-old stars there (in what used to be that Vorwerp, cause it will probably look very different and more like a dwarf galaxy…if it hasn’t by been swallowed by the host galaxy in the meantime) that the Vorwerp stars aren’t just a mere 650 million years old, but that they’re REALLY over…aaack…back to sleep, and ad nauseam throughout eternity. 😯

    Wake me up when we stop making silly mistakes instead. Oh. That might take even longer. Sheesh. Never mind. 8)

  54. Jesper

    Oh come on commenters, do we have to have the argument *again* of the exact translation of the Dutch word “voorwerp”? Does it really matter if you translate it with “thing” or “object”?

    Every time Phil mentions it on his blog this discussion starts again in the comments…

  55. Jojo

    @Anchor. Whew…

    I think you were trying to make a point but for the life of me, I can’t figure out what it was.

  56. oIo


    no it is not the most important thing in the world but a translation is either wrong or right or as right as possible within context. With that attitude we can just start making up what words in other languages mean and end up with young women suddenly being virgins bearing children.

    The Dutch word voorwerp is correctly translated to the English word object . No discussion needed, it is how it is.

    (in German it would be Objekt by the way, as in Danish and Swedish and also French -but then without the k)

  57. Cool photo, that big green mass is a troop of martians migrating to a new planet, everyone knows that :)

  58. Grey Lens

    Anchor, what are you trying to say? If you are trying to espouse that time does not exist, which many theorists now believe may be the case, you did not communicate well.

    Assuming we leave that out of our discussion and assume time does exist… Photons travel at finite speeds (yes speeds, speed varies dependent on medium), ergo the images we observe are of an earlier time. Even the sunlight outside our door left the sun approximately eight minutes ago. We really do not know if the sun is still there as we observe it, we have evidence it was there eight minutes ago.

    As we observe objects at increasing distances we observe them as they existed longer ago. Is it confusing to try to set a distance to these ancient objects? Yes! Are we talking about how far away they are (from us, not from a variant viewpoint) now, or how far were they when these photons began their journey?
    There is no clear standard to which everyone weighing in adheres (actually pro’s simply refer to the red shift and avoid the confusion). The point that relativity will give observers at some third location a different result is truly irrelevant to what we observe.

    It would be more accurate to say those stars are believed to have been around 2 million years old when the light we are observing began its journey to us approximately 650 million years ago based on our current interpretation of the red shift.

    Do you think we should require everyone who discusses matters like these to couch each statement in such a “politically correct” manner?
    I opine that it would not be an improvement over the current imprecision.

    Yours truly, Grey Lens.


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