Two Galaxies Walk Into a Bar…


Two galaxies walk into a bar. The young, regular spiral galaxy and the mature, barred spiral both order a drink. But the bartender only gives a drink to the barred spiral galaxy. The regular spiral galaxy says, “Hey, why didn’t I get my drink?” The bartender replies, “You’re too young, plus we don’t serve your type.”

Extremely lame joke, I know. But now that I have your attention, one of the latest studies conducted by the Hubble Space Telescope show that barred spiral galaxies were less plentiful 7 billion years ago than they are today. This confirms the idea that bars are a sign of galaxies getting older and reaching full maturity; they are no longer in their “formative years.” Using Hubble’s Advanced Camera for Surveys, astronomers say this study of the history of bar formation provides clues to understanding when and how spiral galaxies form and evolve over time.

And if anyone can come up with a better “two galaxies walk into a bar” joke, post it in the comments below. The winner gets a free subscription to Universe Today.

Hubble looked at more than 2,000 spiral galaxies in the Cosmic Evolution Survey (COSMOS). A team led by Kartik Sheth of the Spitzer Science Center at the California Institute of Technology discovered that only 20 percent of the spiral galaxies in the distant past possessed bars, compared with nearly 70 percent of their modern counterparts.

Bars have been forming steadily over the last 7 billion years, more than tripling in number. “The recently forming bars are not uniformly distributed across galaxy masses, however, and this is a key finding from our investigation,” said Sheth. “They are forming mostly in the small, low-mass galaxies, whereas among the most massive galaxies, the fraction of bars was the same in the past as it is today.”

The findings have important implications for galaxy evolution. “We know that evolution is generally faster for more massive galaxies: They form their stars early and fast and then fade into red disks. Low-mass galaxies are known to form stars at a slower pace, but now we see that they also made their bars slowly over time,” he said.

Artist's illustration of the Milky Way.  Credit;  NASA
Artist's illustration of the Milky Way. Credit; NASA

Our own Milky Way Galaxy was recently determined to have a central bar. Our galaxy is another massive barred spiral, and its central bar probably formed somewhat early, like the bars in other large galaxies in the Hubble survey. “Understanding how bars formed in the most distant galaxies will eventually shed light on how it occurred here, in our own backyard,” Sheth said.

COSMOS covers an area of sky nine times larger than the full Moon, surveying 10 times more spiral galaxies than previous observations. In support of the Hubble galaxy images, the team derived distances to the galaxies in the COSMOS field using data from Hubble and an assortment of ground-based telescopes.

Astronomers believe bars form when stellar orbits in a spiral galaxy become unstable and deviate from a circular path. “The tiny elongations in the stars’ orbits grow and they get locked into place, making a bar,” explained team member Bruce Elmegreen of IBM’s research Division in Yorktown Heights, N.Y. “The bar becomes even stronger as it locks more and more of these elongated orbits into place. Eventually a high fraction of the stars in the galaxy’s inner region join the bar.”

Bars are perhaps one of the most important catalysts for changing a galaxy. They force a large amount of gas towards the galactic center, fueling new star formation, building central bulges of stars, and feeding massive black holes.

“The formation of a bar may be the final important act in the evolution of a spiral galaxy,” Sheth said. “Galaxies are thought to build themselves up through mergers with other galaxies. After settling down, the only other dramatic way for galaxies to evolve is through the action of bars.”

Yes, there’s always lots of action in bars. Especially when two galaxies walk in.

Original News Source: HubbleSite

42 Replies to “Two Galaxies Walk Into a Bar…”

  1. Best joke? Free subscription to Universe Today!? Ooh – I’ve got one! Uhh, waaait a minute…

  2. If your uncle Jack helps you off of an elephant,
    Will you in turn help your uncle Jack off an elephant…

  3. Two galaxies walk into a bar and the spiral galaxy orders two bottles of bud.

    “I’ve got no problem serving you” says the bartender, “but your friend will have to leave.”

    “Why?” asks the spiral galaxy

    “Because he’s barred!”

  4. An exploding star walks into a Mexican bar, orders a drink, and just sits. And sits. And sits.

    Everybody wonders why he doesn’t go home, until they realize he’s a nova.


  5. Two galaxies walk into a bar…

    The other patrons were star-struck.

    Thanks! I’ll be here all week!

  6. a galaxies walk into a bar.
    Bartender says, “what’ll it be?”
    Galaxy says, “I’ll have a cosmopolitan”


    (terrible, I know)

  7. Two galaxies walk into a bar but before ordering drinks, one galaxy turns to the other and says “Hey, pretty big in here isn’t it?”

  8. Aaaaaah! They jokes! They hurt!

    But…cannot resist…

    Two galaxies walk into a bar. They both exclaim at the same time, “Ach! Who put this stupid piece of metal here?!”

  9. Two galaxies walk into a bar. One orders a beer , the other orders prune juice.
    “Whats up with that? says the galaxy with the beer.
    The other galaxy replies “I have been irregular for so long, I feel like I have a black hole in my core.”.

  10. Just curious. Why is there only one “bar,” and that bar is (essentially) straight? Could there ever be two bars, forming an “X”? Or could a bar be bent, with one stub at the 12 o’clock position and the the other stub at the 4 o’clock positon? Lots more to learn about galaxy evolution.

  11. A middle-aged galaxy walks into a tavern with a younger date. Both order a drink, but the bartender only serves the younger one. When the older galaxy asks why, the bartender says “The young one is prettier, besides, you have your own bar.”

  12. Two galaxies were on the verge
    of the process of beginning to merge.
    It wasn’t just luck,
    But a cluster f…
    Due to their relative urge.

  13. Two spirals walk into a bar. Bartender notes their close interaction and throws them out saying, “We don’t allow mice in here!”.

  14. Two spirals walk into a bar. Bartender refuses to serve them as his spectrometer shows they exceed the ethanol limit.

  15. Two spirals walk into a bar. They order two drinks each but the bartender points out they have no hands. They respond, “yeah, but we got two arms”.

  16. I have read both Nancy’s and the NASA prerelease and was a little shocked with the mixed messages presented in both articles. I am unsure why both miss the current researches into barred sprial galaxies and the significant improvement in the evolution of barred spirals. Both misses out on the recent discoveries into this interesting topic – the nature of barred spirals themselves!

    To make clear and give an explain; There is strong implication that the evolution of the barred spirals are both sonewhat transitent for galaxies of this sort.

    The quote of Brudce Elmegreen – a staunch investigator of galaxy formation and evolution is quoted only in saying; “The tiny elongations in the stars’ orbits grow and they get locked into place, making a bar. The bar becomes even stronger as it locks more and more of these elongated orbits into place. Eventually a high fraction of the stars in the galaxy’s inner region join the bar” explains how bars are forned, but it doesn’t explain there dissolution and their general instabilities.

    As for the evolution of galaxies, there is a view that there is during the formation of galaxies that there is significant transfer exchange (c.99%) of angular momentum between the central disk out to the spiral structure. [1] As they evolve, they reverse this exchange, and instead tend to form a single bar in the core of the galaxy

    It has been known for sometime, that there has some strong evidence that the spiral arms are feeding gas into the central regions by sprial patterns. This seemingly explains the unexpectedly bright nuclei of some Sc or Sd sprials. I.e. NGC 1300 in Eridanus, NGC 1097 and NGC 1365 in Fornax.
    One of the best recent papers explaining the phenomena (via simulations) was made by Bournaud et al. (2005), who found their lifetime as finite, and these may only exist of one to two billion years before disintergrating. He explains that the bars eventually; “weaken due to growing central mass concentrations, and due to the gravity torque and angular momentum transfer from the infalling gas to the stellar bar.”
    Bournaud (2005) [2], again explain this in a seperate paper, he says; “But another overlooked mechanism, the transfer of angular momentum from the in falling gas to the stellar bar, can also strongly weaken the bar. In addition, we show that gravity torques are correctly reproduced in simulations, and conclude that bars are transient features, with life-time of 1-2Gyr in typical Sb-Sc galaxies…”

    Even more recently, Dabattista & Victor (2006) investigated the disk structure in barred spirals bt doing computer simulations and mesing with the parameters. Here they found other torque effects were placed on the bar, determining that; “We find that bars are robust structures that survive buckling and require a large (~20% of the total mass of the disk) central mass concentration to be destroyed.”

    An example of some of the computer simulations and investigations into barred sprils as made recently by Saigo [5]

    “The bar mode changes the… disk into a fast-rotating bar. The angular momentum is transferred from the bar to the outer infalling envelope, and spiral density waves are emitted outward. The bar shrinks into a smaller round disk after the angular momentum transfer. This increases the accretion rate temporarily. The disk grows through accretion and becomes unstable against the bar mode again. Accretion is dynamical and that its rate is highly variable in the early disk.”

    Those interested in the dynamics and evolution of barred spirals should see Sellwood (1996) [6]

    This better explains the last paragraph of Nancy’s article, which states;
    “The formation of a bar may be the final important act in the evolution of a spiral galaxy,” [Kaitik] Sheth said. “Galaxies are thought to build themselves up through mergers with other galaxies. After settling down, the only other dramatic way for galaxies to evolve is through the action of bars.”

    There is also some recent work on barred spirals, in that they may form, dissolve, then form again over several billion years, whose process ramps up the star formation, then relaxes for a while, reorganises, then starts the process again. They may also do so in different periods, depending on the size of the galaxy and the way they were organised when they ere first formed.

    Again, like most of the star formation regions, angular momentum. its conservation, and dissipation of its energy are the keys to the
    final outcomes of the celestail object we observe. (Its a pity that we don’t educate novices of its importance and fundemental importance in object formation and evolution. Were it so, ths Press Release may have had far more impact.

    As a comment, I think the problem with the NASA Press Release from the Hubble SIte is that it it too slick for what it is trying to explain to the novice or advanced novice.


    As too the “joke”, I think it is a terrible distraction from the gist of the article, and from the responses I figure that many have missed the point altogether.

    Two galaxies walked into a bar and said; “let’s go ballroom dancing” In barred spirals, at least, their mutual gravitational embrace is far more elegant. (Also the closer you move together, the faster you go – courtesy of the conservation of angular momentum.

    [1.] Jan Palous “The Evolution of Galaxies”. (2007)

    [2.]Bournaud, F.; Jog, C. J.; Combes, F. (2005) “Galaxy mergers with various mass ratios: Properties of remnants”

    [3.]Bournaud, F., Combes, F., B. Semelin: MNRAS., 364, L18 (2005).
    “The lifetime of galactic bars: central mass concentrations and gravity torques.”

    [4.] Debattista, Victor P., “The Secular Evolution of Disk Structural Parameters” ApJ., 645, 209 (2006)

    (5.] Saigo, Kazuya; Hanawa, Tomoyuki; Matsumoto, Tomoaki; “Evolution of First Cores in Rotating Molecular Cores” ApJ., 645, 381 (2006)
    [6.] Sellwood, J. A.; Bar Formation, Evolution and Destruction.

  17. Two galaxies walk into a bar and to their horror see the Eagle nebula wrestling and penetrating a rouge black hole with one of its “elephant” trunks. The nebula then retracts the trunk and turns to the galaxies and says “I would like to see any galaxy do that!”. The younger of the two galaxies floats over and says “I think I can do that, but don’t know if I can open my black hole that wide”… 😉
    I know, I know…

  18. Two galaxies walk into a bar and start to order a drink. The Bartender says “Hey, how’d you two get in here!!” The two galaxies look at each other, confused. “Uh, we walked in here.” Said one of the galaxies. “Thats impossible!” Says the bartender, “You don’t have any legs.”

  19. Two galaxies walk into a bar…

    The old galaxy says “have you read Universe Today?”

    The young galaxy replies “it’s ghey.”

  20. two galaxies and a rabbi walk in to a bar.

    the first galaxy orders a glass of mogen david.

    the rabbi looks at him and says, “that’s funny, you don’t look jewish.”

  21. Two galaxies, one old, one young, get in line for entrance into a posh nightclub. Once they finally get up to the door, only the young one is allowed in.

    “Why can’t I get in?” says the older galaxy.

    The bouncer says, “Because you’re a barred spiral, that’s why!”

  22. Two spiral arm galaxies walk into a bar. The mature one orders a a Pan-Galactic Gargle Blaster. The bartender looks at them and gives the mature one the drink. His ID showed he was 42. The younger one wasn’t subsequently barred and blown up by the vogons to make way for a space way 🙂

  23. Two galaxies walk into a bar called the meaning of Life……and as soon as they walk in there’s a mixture of scientists and religious people scattered all around the floor …..
    The two galaxies sit down , call for the bartender abd get their drinks , the galaxies then realize there’s a person at the end of the bar , They then called for the bartender again , the bartender angrily answers ” What??? YOU guys are drunk already!!! , the galaxies respond pointing at the guy at the end of the bar and exclaim ” no , but he is ” …the bartender calmly counters ..” no , he came in like that “

  24. Two galaxies walk into a bar, but before they can even order any drinks the bartender stops them and says “I’m sorry, we don’t serve food!”

    …think about it…

    …does this joke only work in the UK?

  25. Two galaxies walk into a bar and ask to see the drinks menu. Four hours later they still haven’t ordered anything and the barman is getting really fed up.

    “If you’re not going to order anything I’m going to have to ask you to leave.” says the barman

    “We do want a drink” says the first galaxy, “but there’s too much choice. We just keep going around and around and around!”

  26. Two galaxies walked into a bar and the place went crazy. Everybody was attracted to them and they were treated like stars.

  27. After being chatted up by a middle aged galaxy for a while a young girl finally loses patience and tells him to “Get lost, creep!”. After he has left the bartender says to the girl “That was a bit harsh wasn’t it? What did he do to upset you?” The girl replies “Well, he was highly irregular and his arms were just everywhere!”

  28. Two galaxies walk into a pub – it was The Spiral Arms.

    There was a “battle of the bands” contest on that night, but they couldn’t take part – they weren’t members of their Local Group.


  29. 2 galaxies walked into their local pub. One says to the barman “I’d like a gin and tonic please and a pint of ale for my friend”. “Certainly sir”, replied the barman. Before drinking the other galaxy says “Is this a lager I see before me, the handle toward my hand? Come, let me clutch thee. To drink or not to drink, that is the question.”

    “Does he always talk like that?”, the barman enquired of his friend. “Well yes, actually”, ansewered the first galaxy. “After all, he is the barred of Avon”.

  30. Bert and George go into a bar each night. The first night they were both immaculately dressed, but the second night Bert’s shoes were dirty and George had lost his tie. Next night George’s jacket was torn and Bert’s hair was unkempt. Each successive evening their appearances had deteriorated somewhat and after a week of this the barman was very curious. “Excuse me gentlemen”, he said, “but I can’t help noticing that you are steadily becoming less well presented, what’s going on?”.

    “It’s very simple”, replied George. “We’re galaxies, and each night we’re Messier”.

  31. Damn it, that punchline should be “We’re galaxies, and each night we’re Messier objects”. That’s why I died on stage there.

    Start the engine please driver.

  32. A galaxy walks into a bar. The bartender says “Hey, we don’t serve drunks in here!”

    The galaxy replies “I’m not drunk, just a little dizzy.”

  33. Two galaxies walk into a bar. After staying most of the evening and consuming a considerable amount, they get up to leave. One turns to the other and says, “Is it just me, or is the room spinning?”

  34. A red shifted galaxy and a blue shifted galaxy walk into a bar together. The barman looks a bit surprised to see them. “I thought you were separating”, he said.

  35. The three very elderly galaxies were sitting in a bar sinking a few beers and reminiscing about old times. “You know”, said one, “I’m so old I can remember when the cosmic microwave background was still in visible light”.

    “That’s nothing”, retorted the second. “When I was young the universe was still opaque and if you weren’t careful you could lose your outer regions and loose arms with the all rapid inflation that was going on”.

    They both looked at their friend, who was sitting quietly. “You haven’t said much tonight, what’s up?”

    “Sorry boys”, he drawled. “I don’t hear too good since that Big Bang went off just behind me”.

  36. After reading through all these, I’m not even going to attempt it – we already have a winner IMO.
    Andrew Guthrie, sir, you are a master. 🙂
    (Several of his are potential winners.)

  37. 2 nervous young galaxies go into a bar for a speed dating evening. “Damn, what a bad day to get a couple of new supernovae”, said one.

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