Flying saucer galaxy!

By Phil Plait | April 7, 2009 9:15 am

Hubble spies invading saucer from space!

Hubble image of spiral galaxy NGC 7049
Click to Brobdignagify.

OK, it’s not an alien spaceship. But Holy Haleakala, what a gorgeous galaxy! It’s NGC 7049, a kind of hybrid galaxy, one that is part disk (like our spiral Milky Way) and part elliptical. These types of galaxies are fairly rare. They are shaped like disk galaxies — a flattened disk surrounding a central bulge — but have almost no gas compared to a normal spiral galaxy. It’s the gas that makes spiral galaxies obvious to the eye. As gas orbits the galactic center in a disk, odd gravitational instabilities build up, creating spiral-shaped traffic jams in the disk. Gas piles up there, collapses, and forms stars. The stars light up the gas, and from a few dozen million light years away, you see a gorgeous spiral galaxy.

But NGC 7049 is not gifted with gas, so the disk is fuzzy and featureless… almost. This galaxy does have a ring of beautiful dust lanes circling the center, which is unusual even for these types of galaxies! We see the dust in silhouette because it absorbs light from stars, blocking the starlight behind it. It takes a considerable quantity of dust to absorb that much light, which is weird– dust is usually formed when there’s lots of star formation. But without gas, NGC 7049 can’t make new stars, and so there shouldn’t be much dust. What gives?

My first thought when I saw this picture was that the galaxy must have recently eaten a smaller galaxy and taken on all its dust. And it turns out that may very well be the case. Studies of these types of galaxies shows that some do have gas, but in some cases the gas is orbiting the galaxy in the wrong direction, the opposite direction as the stars do. That’s a sure sign that a smaller galaxy got too close, collided with the larger galaxy, and finally merged with it. In some of those events the geometry of the collision with smaller galaxy will yield a counter-rotating block of stars, gas, and dust.

So that’s probably what happened to NGC 7049. And now, a few hundred million years later, we reap the benefit of being able to see this spectacular and lovely galaxy.

Image credit: NASA, ESA, and W. Harris (McMaster University, Ontario, Canada)

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (51)

  1. Joe Meils

    Wow. I got the same sort of thing when I stir my coffee creamer in, then add a sprinkle of chocolate powder to the foam. Stir lightly.

  2. OtherRob

    Thanks for posting that. It’s just incredible.

    Is the bright object at 1 o’clock a star in our own galaxy or something serious happening in the NGC 7049?

  3. Amy F.

    It’s a foreground star in our galaxy.

  4. Cheyenne

    “Brobdignagify”? Is the BA creating new additions to our dictionaries? Shweeeeeet….

    I never knew you could have counter-rotating gas, stars, dust, etc when two galaxies merge. I love me some new science learnin’ from this blog.

    Hope all goes well with the Hubble repair mission. These photos are just awesome.

  5. TheBlackCat

    OK, it’s not an alien spaceship.

    That’s just what they want you to think.

  6. “Which shall it be, Passworthy? All the universe, or nothingness? Which shall it be?”

  7. Todd W.

    @Amy F.

    It’s a foreground star in our galaxy.

    That made me think of a question: have we ever observed a star not in a galaxy? A lone star (or small cluster) out between galaxies? I’m guessing no, but is it something that could be possible? Perhaps from the collision of two or more galaxies, some of the stars get flung away…

  8. Jeff

    very interesting

    or , the dust may be the remnants of a wild burst of supernovae early in this galaxy’s history, which blew out the remaining gas and left only supernovae products behind

  9. dWhisper

    One of my favorite things about this blog (and quite honestly astronomy in general) is learning something new and surprising in just about every read. Like the commentor above, I had no idea that you couldget a counter-rotation in a galaxy. And that just brings a few more questions to mind… will the two rotating masses interact with one another enough to cause bursts of formation usually seen with these collisions? I get that a huge chunk of what we see is empty space, but I’m curious how two distinct masses moving through the same space in opposite directions would interact.

  10. @Todd –

    My favorite picture that Phil has posted was the one of Mira flying through space (Top Ten 2006). Big bruiser of a star that is traveling at 291,000 miles per hour. It’s in our galaxy but if there are stars that are cruising around that fast it wouldn’t surprise me if they could escape a galaxy. But does anybody have a definitive answer to Todd’s question? I think that is pretty interesting too.

  11. “My first thought when I saw this picture was that the galaxy must have recently eaten a smaller galaxy and taken on all its dust.”

    Nobody likes a cosmic bully.

  12. Erasmussimo

    The explanation is obvious. This was a bad little galaxy when it was a boy, and it never picked up after itself as its mother tried to teach it to do. Now it’s covered with dust. It should be dubbed “The Pigpen Galaxy”.

  13. It’s obviously a crown of thorns.

  14. *sighs*

    The universe is just so friggin’ HUGE….!

  15. Brian

    There are certainly lots of pictures of galaxies that have been disturbed by a close pass with another galaxy, causing stars to get flung outward in little streamers (and in some cases triggering the creation of new stars). Does that count?

    Or how about globular clusters? Those are often referred to as satellites of their galaxies.

    (Really, in order to answer Todd’s question, you need to define where exactly a galaxy ends. They don’t have clearly defined borders.)

  16. Gary Ansorge

    That is so cool,,,no, really, it’s cool as in not particularly energetic.

    Todd W: Our sun is revolving around the Milky Way at about 18 miles/sec or about 64,800 miles/hr. So Mira, at 291,000 mi/hr could easily leave this galaxy far behind. I expect there are expelled stars, traveling the intergalactic void but they would be hard to find. So dim against the galactic noise,,,

    GAry 7

  17. Gary Ansorge

    Oops. I goofed. The suns velocity around the galactic core is about 220 km/sec, not 30,,,” mumble, mumble,,,recalculating,,,).
    ,,,so that would be about 480,000 mi/hr. Mira at 291000 mi/hr would therefore still be constrained to this galaxy,,,

    ,,my bad,,,

    GAry 7

  18. Wow, that really is gorgeous. Thanks for posting this image :)

  19. DavidHW

    I came here to say precisely what Naked Bunny with a Whip did. LOL. You just *know* someone will say this is a sign given unto us for the Easter season to renew our faith.

  20. Icepick

    Every time I see a shot like this it takes me a couple takes to shake “artist rendering” out of my head and push “REAL” in. Just amazing.

    The thing I always want to know is relative distances of the other objects. Obviously, some are much farther away while the star at one o’clock I take (from other posters) is much closer.

    It would be cool if you could zoom these shots ala Google Earth.

  21. I have nothing witty nor profound to share, because I am just in awe of that photo.


    Thanks for sharing, Phil.

  22. Joe Meils

    Todd W.,

    It happens all the time. Stars are often kicked out of a galaxy when the two collide, or other gravitational disruptions. In fact, I remember reading somewhere, (maybe Astronomy a few issues back?) that our sun and others on the outer rim of the Milky Way stand a good chance of getting kicked out when we collide with Andromeda, billions of years from now. (provided our solar system is still around by then)

  23. Retrogarde

    When does it stop? Every time you think you’ve seen it all there is just another gorgeous picture with features never been seen before. It’s amazing. Thank you for posting this.

    Now I think of it, when we see clouds of dust, is this really dust i.e. tiny particles, or is there debris, asteroid like objects and (wandering) planets as well?

  24. Todd W.

    @Joe Meils

    I understand that it is possible for a start to get flung out of a galaxy; just wondering if it has ever been observed. Do we have any pictures of a star that is outside the bounds (whatever those are) of any galaxy?

  25. Siphoneuphoria

    Aw, and I just made a Volcano picture my background… decisions… decisions.

    Hey, maybe it’s Dust

  26. dWhisper


    My understanding is that such a view would be extremely unlikely, but not exactly impossible. I don’t think there are any pictures of lone stars, but plenty of objects that straddle the lines between stars and galaxies have been observed.

    Ultimately, a star “between” would need to have sufficient mass/luminosity that we could see it, and as stated by an earlier comment, the edges of a galaxy aren’t clearly defined (and much larger than what we see). Globular Clusters, for example are in that grey area between something in our galaxy and something orbiting it (as are a lot of dwarfs). We’ve imaged them simply because there are so many.

    But the chance of catching a rogue just wandering, gravitationally unbound, is remote, since we might not be looking for it, or able to distinguish it from fore or background stars. We’ve undoubtibly imaged them before, but being able to recognize it as such. What we have seen are stars that are escaping our galaxy, exceeding the speed of the rest of the stuff around it). HE 0437-5439, for example, is currently “in” the Milky Way, but not bound to it. In fact, it originated in the LMC, and just happens to be cruising through our little corner of the galaxy. Eventually, it’ll be out of it, and into the darkness again.

    I tried searching, but didn’t come up with a concrete answer that we have/have not seen anything in between, but it’s certainly an interesting question.

  27. Todd W.


    Thanks for the response. I wonder, will the first such confirmed lone star be nicknamed “Texas”?

  28. Click to Brobdignagify.

    Hm. When I clicked, it ginormicated. Should I check my software?

  29. OtherRob

    It’s a foreground star in our galaxy.

    Thanks, Amy F. I figured it probably was on the theory that if it had been, say, a massive supernova in the far galaxy that Phil would’ve mentioned it. :) But I appreciate the confirmation ’cause I’m not an astronomer and I don’t even play one on tv…

  30. Didac

    The greatest flying saucer-looking galaxy is Sombrero Galaxy (M104).

  31. Maybe it’s my age, but ‘male pattern baldness’ came to mind at first sight.

    Imagine the comb-over!


  32. Gary Ansorge

    As a hair challenged friend once told me, ” We all start out with the same amount of testosterone, some just waste theirs growing hair,,,”.

    I guess this galaxy saved theirs for some other use??? Hope they’re having fun out there.

    GAry 7

  33. QUASAR

    How far away is it?

  34. Amy F.

    @Todd W.
    I don’t have a link onhand but I believe there have been “lone” stars observed in dense galaxy clusters that have presumably been flung out of their parent galaxies by all the close encounters/mergers that occur in those clusters.

  35. At around 11 o’clock in that picture, there’s what appears to be a dwarf irregular (satellite?) galaxy… Kinda reminds me of Optimus Prime.

    (And I’m sorry, I don’t know why I keep making Transformers references when I post here. Believe me, I don’t anywhere else!)

  36. Astro-doh

    So is the glowing stuff stars, or gas or what?

  37. wench

    That’s so beautiful. Felt crappy this morning; glad to wake up to something so lovely in my tweetstream.

  38. dre

    Unbelievable pictures like this lead me to believe that astronomy is a centuries-old conspiracy, and all we’ve ever seen are “artists’ renderings”. I just can’t figure out how so many attention-starved nerds could keep such a huge secret for so long.

  39. meadcd

    guys, come on … it’s not “Brobdignagify”, it’s “BrobdiNgnagify” … sheesh…

    for those as confused as i was:

    Brobdingnag: the region in “Gulliver’s Travels” where everything was bloody huge :)

  40. Gary Ansorge

    Nerd conspiracies are all over the place. Artists, by their very nature(seeking to expose the figure locked within the stone), spill secrets indiscriminently . NErds aren’t as attention starved as they/we seem,,,

    GAry 7

  41. Okay, this made me gasp.

  42. You say “But NGC 7049 is not gifted with gas.”

    Ah, but if only the same were true of Rush Limbaugh.

  43. Jon

    I’m just going to post what I said out lous when I saw this picture:


  44. Kevin Mason

    I wonder both types of galaxies are in fact the same, but at different stages of development. Maybe this image caught the change from elliptical to a spiral?

  45. Torbjörn Larsson, OM

    Oh, so what’s where the Xeelee works their astromagical extradimensional ring circus!

    Click to Brobdignagify.

    Oh, that’s so Swift boating! The peninsula was Brobdingnag and the link actually Lilliputify the image.

    I suddenly feel like I’m visiting a Houyhnhnms’ blog.

  46. Robert Carnegie

    Since the discovery that most of the mass of many galaxies is “toxic” dark matter, they have to be taken over or merged with larger galaxies to stay in business. I for one welcome the new incoming board of AndroMilky. Of course we all knew Barack Obama would do what it took to save the universe, but, well, done, Mr. President!

  47. alfaniner

    “You just *know* someone will say this is a sign given unto us for the Easter season to renew our faith.”

    Fox”News” headlined their article “‘Crown of Thorns’ Galaxy Photographed in Space”, although no mention of that term was used in the article proper.

  48. !astralProjectile

    And in other flying saucer news: $250 and 50 hours of community service for hoaxing UFOsters. (Actually fire/air traffic dangers)

  49. Chaplain Rich

    GOOD FRIDAY IS TOMORROW AND YET GOD REMINDS US IN THIS PHOTO THAT HE IS IN CONTROL AND HE LOVES US SO MUCH THAT HE SENT HIS ONLY SON WHO BORE OUR PAIN AND SUFFERINGS!! Luke 21:11 (New American Standard Bible) and there will be great earthquakes, and in various places plagues and famines; and there will be terrors and great signs from heaven.


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