Galaxy on edge

By Phil Plait | November 8, 2010 8:42 am

Spiral galaxies are among the most magnificent objects in space. Grand and sprawling, they are icons of the night sky.

Like a snapshot of coins tossed in the air, we see them at all angles, from face-on disks to nearly edge-on lines. And sometimes we catch them so precisely to the side that what we see is hard to believe is real. But then we get pictures like this one from Hubble of the galaxy NGC 4452:


[Click to galactinate, and yes, you really want to.]

Holy perpendicularity!

There are lots of edge-on galaxies in the sky, like NGC 253 and NGC 4710, but this one is extraordinary. The alignment is perfect, and the disk is incredibly thin. Our Milky Way is 100,000 light years across and 2500 or so light years thick (a ratio of 40:1), but NGC 4452 looks even thinner than that; measuring off the picture I get a width-to-thickness ratio of 100:1.


eso_ngc4565Other things are obvious, too, and honestly a bit weird. For one thing, the central bulge of the galaxy is very small; in most edge-on galaxies it pokes above and below the disk like in NGC 4565, shown here. In that picture you can also see lots of dark dust; that’s actually complex organic molecules that are very efficient at absorbing visible light. They’re created when stars are born and when they die, and dust clouds tend to huddle close to the center of the disk.

[Note added later: It occurs to me there might be dust in the galaxy despite what I say in the next paragraph. That’s because dust doesn’t show up in the infrared very well, and one of the filters used was IR (as I note in a following paragraph). Also, the kind of camera used isn’t as sensitive in the blue as it is in the IR, so that might also suppress seeing any dust that might be there. So take the next paragraph with — haha — a grain of salt.]

But NGC 4452 appears denuded of dust! I’ve never seen a galaxy quite so clean. I think it would actually pass the white glove test. As it happens, this galaxy is part of a nearby cluster called the Virgo Cluster, a collection of hundreds of galaxies about 60 million light years away. In between the galaxies is a thin fog of gas, and as the galaxies orbit each other they plow through this gas. The high speeds at which they travel can actually strip them of their own gas and dust, like when you open your car window while driving to get rid of, um, say, an obnoxious smell. Perhaps this is what happened to NGC 4452.

The disk is surrounded by a fuzzy glow, which would be the collected light from billions of stars above and below the disk. Note that if you look to the extreme edges of the disk, the fuzzy glow appears to subtly bend down on the left and up on the right. The galaxy is warped! This is common in disk galaxies (the Milky Way and nearby Andromeda galaxies are warped, and you can also see it in NGC 5866). It’s usually caused by a gravitational torque, an off-center tug, from a nearby galaxy. Since NGC 4522 is in a cluster, it’s not too surprising there might be some galaxy that could do this.

And finally, one more thing. Look at all the distant background galaxies in the picture! There are dozens of them scattered about, most much, much farther away. Mind you, this picture of NGC 4452 is a short exposure; just a combination of 12.5 minutes using a blue filter and 20 using an infrared one. This means the sky is filled with galaxies!

And each one is an island Universe, made of billions of stars along with massive gas and dust clouds, and each as spectacular and amazing as this one seen up close.

Image credits: ESA/Hubble & NASA; ESO

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (49)

  1. Practice

    Just want to point out, the galaxy disk doesn’t appear to be uniform, its glow fades in and out.

  2. Chris

    Somewhere in one of those galaxies an alien is looking back at our little smudge of a galaxy wondering what kind of life is living there and realizing there is no way it’d ever be able to find out.

  3. The Mutt

    There is nothing wrong with your television set. Do not attempt to adjust the picture. We are controlling transmission. If we wish to make it louder, we will bring up the volume. If we wish to make it softer, we will tune it to a whisper. We will control the horizontal. We will control the vertical. We can roll the image, make it flutter. We can change the focus to a soft blur or sharpen it to crystal clarity. For the next hour, sit quietly and we will control all that you see and hear. We repeat: there is nothing wrong with your television set. You are about to participate in a great adventure. You are about to experience the awe and mystery which reaches from the inner mind to… The Outer Limits.

  4. The Mutt: that was exactly my first thought as well. :)

  5. kkozoriz

    “In this galaxy there’s a mathimatical probability of three million Earth type planets, and in all the universe three million million galaxies like this, and in all of that, and perhaps more, only one of each of us. Don’t destroy the one named Kirk.”

    McCoy to Kirk, in the episode “Balance of Terror”

  6. Jeff

    “Holy perpendicularity!”

    you got it , buddy. I’ve never in my life seen one that edge-on view,

    we are living through amazing times in astronomy and this blog is one good window to it.

    I remember in 3rd grade, the closest I got to science was when they had the kids order two scholastic book service books for probably five dollars and I ordered “planet X” and “the ice ages” , if you remember those old-style books.

  7. Robert

    What would the effect of the lack of dust be on star (and planet) formation? If stars form from collapsing gas/dust clouds and all that gas and dust has been blown away, does that mean this galaxy consists of only older stars and that no new ones are being formed?

  8. Amazing to find a galaxy evidently so undisturbed by strong interacctions in the Virgo cluster. Is it way out in the fringes?

  9. Bouch

    Looks to me like we’re looking into the top of the monolith. “My god, its full of stars!”

  10. Bob_In_Wales

    With apologies to Brain Aldiss …

    Galaxies Like Grains of Sand!

  11. Should be working

    OH WOW!!!! It would be futile of me to ask that you stop posting neat, awe-inspiring stuff while I’m working, wouldn’t it. Could you save the ‘oh wow lookit-that!!’ science until my next staff meeting? (2nd Thursday of the month) This makes a mockery of the blog name, you know.

    Keep up the super posts. My science students are gonna get a brain-full of astronomy this term!

  12. RickJ

    There’s an entire catalog of flat galaxies that lists 2574 at NED or 2573 in the original listing.….314…97K (a near 13 meg PDF download)

    Oddly NGC 4452 isn’t in the list.

    In my imaging of galaxies I’ve picked up many such edge on, bulge-less galaxies. Some in the catalog others not. They are more common than I’d realized. Most however are either far smaller or further away as they are quite tiny in angular size. NGC 4452 may be the closest.

    I love strange galaxies like these. They have a lot to teach us once we figure out why they are strange. See Universe Today for a “new” supernova in a very strange looking smudge of a galaxy. Well two apparently tearing themselves apart. I found them more interesting than the SN. Tried an image in dawn skies. I’ll post to Baut’s astroimaging forum when I get it processed in a day or two. SN was so bright it pretty well drown out its galaxy so will take some processing to separate the two.


  13. andy

    Given the low dust levels I’d guess NGC 4452 is a lenticular galaxy rather than a spiral. Lenticulars don’t seem to get much attention outside the scientific literature, which is a shame.

  14. It almost looks like an edge-on view of the slowly rotating monolith orbiting Jupiter in 2001: A Space Odyssey.

  15. Chris

    As the man says, Hubble gotchu.

  16. Chris

    On the left of the center, there’s a star visible… has it been determined if it is part of the galaxy or if it’s in front of it?

  17. John D (Vancouver)

    Absolutely awesome! Thank you for this!!

  18. JohnW

    Looks like the HBO logo they show before a show starts.

    I half expect to hear the “Curb Your Enthusiasm” tuba start up.

  19. What’s really cool is that I count over 200 galaxies in that photo.

  20. Kyle

    Thing I noticed is if you move the side to side rapidly there almost appears to be a “dark” ( of smudge of darkness) X around the central bulge….optical illusion or a structure in the disk? Inquiring minds want to know.

    Ditto Squid but I didn’t count I just saw a whole bunch.

  21. I see your NGC 4452 and raise you NGC 4762 (more pictures here), which is also dust-free, also has an outer warp, and is also in the Virgo Cluster. (Alas, the image is not quite as stunning, since it’s not a mosaic of multiple exposures and no one’s rotated the galaxy to horizontal.)

    andy @14: Yes, NGC 4452 is a lenticular galaxy.

  22. Rob Knop @ 8:
    Actually, NGC 4452 is pretty close to the center of the cluster, at least in projection. (But it might be away from the center along our line of sight; unfortunately, there isn’t a direct distance measurement for it, so it’s rather hard to tell.)

    RickJ @ 13:
    I think the Karachentsev et al. catalog you mention was meant to include only very thin, edge-on spirals (which are likely to have measurable gas in them); lenticular galaxies like NGC 4452 were probably left out deliberately.

  23. AJ in CA

    I had no idea there was enough material in extragalactic space to have any discernable effect on galaxies themselves.

    I wonder if any of that gas (including whatever is knocked off of passing galaxies) will ever coalesce into a globular cluster?
    Is it possible that after the last galactic stars have formed and grown old (there being more perturbations and shockwaves inside galaxies to force gas together) that a few lonely stars might one day form in the space between the galaxies, after a trillion years of extremely slow contraction and collisions?

  24. Lavocat

    There appear to be four “nodes” in the disk as well: one on each end and a pair towards the center, juxtaposed to the core.

  25. AJ in CA

    I love these deep-field photographs, showing untold numbers of distant galaxies in the distance. Our own galaxy is mind-bogglingly big enough…

    It’s humbling to think that even if we as a species manage to survive and explore and pull off an Asimovian feat of epic colonization, ultimately expanding across the whole Milky Way, exploring billions of worlds over hundreds of millions of years – even if our most hubris-filled sci-fi scenarios one day came true… Even then, we’d STILL only have managed to discover and occupy a few tiny parts of one single galaxy that exists among billions, stretching out further then we can reach or even see.

    Even as gods, the universe would dwarf us utterly.

  26. Darren Evans

    The lack of central core bulge is odd.

    I’m going to naively as if it’s possible that there’s not a single black hole at the centre but two black holes orbiting each other around a central point?

    Is such a formation of black holes even possible in Galaxy formation?

    How far apart would they have to be to have such a minimal bulge effect on the central stars?

    I’d also guess two orbiting black holes in a Galaxy would make for unusual spiral arm arrangments if we viewed the Galactic disc from above but our view is obviously edge on.

  27. AJ in CA

    @#27 Darren Evans: Well, binary stars are quite common, particularly in the crowded space near the center of a galaxy, and if both stars are massive enough, they should collapse into black holes when they “die”. I’m not sure if supermassive black holes form differently then regular black holes, or simply form and then accrete lots of matter (and maybe other black holes as well).

    This is just speculation on my part, but I think that a supermassive clump of gas and dust can never collapse straight into a black hole, because before that happens, the material will form a very high mass star, and at a certain ultra-high mass, a star is hot enough that its radiation pressure blows off its outer layers (and any other gas in the area – this is the Eddington Limit).
    This would mean that even supermassive black holes would form first as “ordinary” large stars that just happened to be in very crowded surroundings, where there’s lots of gas (and stars and anything else) to slurp up once the black holes form at the end of the stars’ life.
    The one thing about the binary black hole idea that I’m really unsure of is what happens to the angular momentum of the holes as they accrete more matter? Do they orbit more closely as they become more massive?
    IIRC, one of the stated purposes of trying to identify gravitational waves through experiments like LIGO was to look for the gravitational disturbances caused by orbiting neutron stars or black holes, as these waves would presumably be extremely strong (as far as gravity waves go) and have an easily recognizable repeating signal.

    Annnnnyway, my (uninformed layperson) opinion is that the answer to the first two questions is “probably definitely, with possible caveats” and my answer to the second two questions is “I have no freaking idea because I’m not a physicist and probably will never be one because I suck at math” :)

  28. Sue

    NGC 4452 doesn’t meet the major axis to minor axis ratio requirement of the Flat Galaxy Catalogue or the Revised Flat Galaxy Catalogue. It would have to be more than 7 times longer than wide, and it isn’t on the blue images used for the FGC or the blue and red images used for the RFCG. Call them up on Aladin and measure for yourself. Perhaps this image appears different because it goes into the near infrared.

  29. Douglas Troy

    Holy Galactic Frisbee PlaitMan! The Universe is amazing.

  30. jess tauber

    Now what we need is a simulation of a spiral galaxy being flipped like a coin. Heads I win. Tails you lose.

  31. Messier Tidy Upper

    @ ^ jess tauber : But the lenticular – & also spiral too – galaxies have neither heads nor tails but just arms! 😉

    EDIT : Although I guess you do get tidal tails … so-oo .. I’d call tails! 😉

    Awesome image, excellent write-up. Thankyou BA. :-)

  32. Messier Tidy Upper

    @27. Darren Evans Says:

    <blockThe lack of central core bulge is odd. I’m going to naively as if it’s possible that there’s not a single black hole at the centre but two black holes orbiting each other around a central point?

    Yes, I think that’s possible and I vaguely recall having seen / heard somewhere that the Andromeda galaxy has such a double nucleus with two black holes at its core.

    Is such a formation of black holes even possible in Galaxy formation?

    I’d think so given the idea that galaxies grow through merger and the consumption of smaller dwarf galaxies. If a galaxy engulfs a few others logically, the other galaxies core should fall inwards and eventually join up but there’d almost certainly be a stage where there’s more than one supermassive black hole in the galactic centre. These Supermasive Black Holes (SMBHs) would attract each other via gravity and likely end up orbiting each other and then merging to form one larger one although I haven’t immediately got any sources for you to confirm that, I’m afraid.

    How far apart would they have to be to have such a minimal bulge effect on the central stars?

    Sorry, this one I don’t know & won’t even venture a guess on.

    I’d also guess two orbiting black holes in a Galaxy would make for unusual spiral arm arrangments if we viewed the Galactic disc from above but our view is obviously edge on.

    Perhaps but not necessarily. If the second SMBH came from another galaxy it would be tidally disrupted and eventually intermingle with the original one and at the core the bulge would seme to hide the effect and the drama from the rest of the galaxy. Two orbiting SMBH’s close to each other would probably, I’d imagine, have as little effect on the surrounding arms as two stars in a tight binary have on orbiting planets – ie. outside of a zone where orbits are unstable or impossible the planets just orbit the centre of the systems mass (barycentre) normally.

    But I could well be mistaken here.

    Does anyone else know more here & care to enlighten us all please? 😉

  33. Messier Tidy Upper

    D’oh : For some reason the first quote from #27 Darren Evans didn’t appear there.

    It’s meant to be :

    The lack of central core bulge is odd. I’m going to naively as if it’s possible that there’s not a single black hole at the centre but two black holes orbiting each other around a central point?

    *Then* my reply to that of :

    Yes, I think that’s possible and I vaguely recall having seen / heard somewhere that the Andromeda galaxy has such a double nucleus with two black holes at its core.


    Although that on checking here :

    It looks like I was wrong about that anyhow. :-(

    Also, might I recomend you ask this on the Bad Astronomy Universe Today (BAUT) forum here :

    as well? (If you haven’t already.) Folks there may be able to find an answer for those too. :-)

  34. RickJ

    Thanks for the information. I was going by Phil’s 100:1 ratio estimate. I didn’t look at the blue POSS 2 plate. See now it has a much larger central bulge than seen in the HST image. Red plate bulge is not as big but still larger than seen in the HST image. Near IR has it even flatter. Some of the difference may be in processing as well as wave length. Easy to bias processing toward flat when that’s the idea in the processors head.


  35. Anchor

    It’s a lenticular galaxy that’s been undisturbed for quite a while. Dust-free lenticular or smooth-armed spiral systems (so-called ‘SO’ systems) are quite rare, and any which might present themselves almost perfectly edge-on to our line of sight would be even more rare. Given the gigantic numbers of galaxies available to our view, however, spotting one and imaging it at high-res with the Hubble (given it’s busy load) was bound to happen sooner or later. But this is indeed an exceptionally beautiful catch!

    If one scans ones eyes slowly laterally along the horizontal, one will notice a very subtle but distinct “X” structure centered on the core region. That comes about from stars imported from another galaxy that have preferentially assumed orbits from some merger in the distant past of this system. The most extreme examples of the phenomenon create what astronomers dub ‘box-shaped’ cores. It’s quite easy to recreate the phenomenon with simple programs that are freely available on the net.

    UFO enthusiasts may now commence declaring this marvelously symmetrical object to be an example of an artificial construct.

  36. Anchor

    Phil says, “Our Milky Way is 100,000 light years across and 2500 or so light years thick (a ratio of 40:1), but NGC 4452 looks even thinner than that; measuring off the picture I get a width-to-thickness ratio of 100:1.”

    You have to be careful not to overplay it. We DO understand that our galaxy’s disk is comprised of an inner and outer disk component, just like every other disk galaxy we see. And it is not very accurate to declare that our galaxy’s disk has a thickness of “2500 or so light years” when our Milky Way’s disk not only sports an inner and outer component, but also exhibits considerable warping from a given plane. The reality is always a might removed from a specific declaration of thickness. For example, many non-optical wavelength surveys of our galaxy plainly show our galaxy’s disk to be either considerably below or above that figure. But if a DIFFUSE distribution of stars alone determines it, one can’t put a figure to it other than by some distributive grounds, such as saying, for example, ‘50% of the stars in the disk are confined within x light years of the midplane”. I do not think that our Milky Way would be significantly different from NGC 4452 in that particular respect.

    But in this particular case with NGC 4452, you obviously discount the outer diffuse component of the disk, which is clearly evident in the image. THAT ratio exceeds 6:1. It’s probably similar to that of our galaxy, as well as any disk galaxy. It is probably NOT terribly special in that regard.

    It is also interesting to see on scanning it horizontally to find vague but significant variations in brightness along the disk that appear to be symmetrically positioned with respect to the core. That indicates that, if viewed perpendicularly to this line of sight (so that we view it face-on), this galaxy would exhibit some structure departing from a smooth distribution with radius.

  37. Aleksandr Motsjonov

    “organic molecules”? o_O WTF?

  38. JMW

    How about this: the Lightsaber Galaxy?

  39. JMW: Exactly what I was thinking! Must be full of jedi in there…

  40. Captn Tommy

    In the “Astronomy Picture of the Day” explaination of this, the galaxy is refered to as Lenticular. This as I believe is a sort of spinning elliptical galaxy, which would explain the star cloud around NGC 4452, and the lack of dust. This could be a very very old galaxy.

    It could be that this galaxy is quite different looking from the diskside view.

    When I saw this picture I for one thought, “Light Sabre”

    Captn Tommy

  41. mocular

    Phil, seems you’ve been scooping APOD recently. Are you getting inside info?

  42. therm

    There is a huge population of stars outside the “disk”, APOD has a link to a document that is actually written by someone who’s done some research on it. The short exposures show the thin disk, long exposures show the extents of the star cloud. Measuring the length and width from that photo is like seeing a face on Mars, the image doesn’t show the entire picture.

  43. Anchor @ 36:

    Lenticular/S0 galaxies are actually not that rare — probably about 10-15% of bright galaxies.

    I’m not sure about an X structure in this particular galaxy; that may be (mostly) an optical illusion. In any case, while such structures could, in some cases, be the result of minor mergers, the majority of them (i.e., so-called “boxy” or “peanut-shaped” bulges) are internally generated: they are the inner, vertically thick parts of stellar bars, seen close to side-on. (And I suspect a significant past merger would not have left this galaxy’s disk as thin as it is.)

  44. Ben Linus

    @kkozoriz: Kirk to Bones: “Shut up!”

  45. Messier Tidy Upper

    @40. JMW Says:

    How about this: the Lightsaber Galaxy?

    I second that. Very apt. :-)


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