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COSMOS Survey. Credit: NASA, ESA, K. Sheth, P. Capak and N. Scoville

Two Galaxies Walk Into a Bar…

29 Jul , 2008

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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


Sort by:   newest | oldest | most voted
Astrofiend
Member
Astrofiend
July 29, 2008 11:37 PM

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

LLDIAZ
Guest
LLDIAZ
July 30, 2008 7:12 AM

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

Chris Parr
Guest
Chris Parr
July 30, 2008 1:58 AM

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!”

Steven
Guest
Steven
July 30, 2008 3:28 AM

Two galaxies walk into the bar.

Barman says to the old one your barred!

Roger, FCD
Guest
Roger, FCD
July 30, 2008 5:08 AM

Two galaxies walk into a bar…

The other patrons were star-struck.

Thanks! I’ll be here all week!

Amir
Guest
Amir
July 30, 2008 8:55 AM

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

HA!

(terrible, I know)

Alan
Guest
Alan
July 30, 2008 5:55 AM

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?”

Mad Scientist In Training
Guest
Mad Scientist In Training
July 30, 2008 6:29 AM

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?!”

kankan
Member
kankan
July 30, 2008 6:38 AM

Two galaxies walk into a bar. The third one ducks.

RALF
Guest
RALF
July 30, 2008 7:27 AM

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.”.

Benneton
Guest
Benneton
July 30, 2008 7:51 AM

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.

Mikel
Guest
July 30, 2008 8:03 AM

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.

Ba-da-bing.

JD
Guest
JD
July 30, 2008 8:18 AM

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.”

Mikel
Guest
July 30, 2008 8:18 AM

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.

John Young | We Have Contact
Guest
July 30, 2008 8:28 AM

Two galaxies wait in line to get into a bar, the bouncer stops them as they attempt to enter.

“Sorry guys, we’re at critical mass.”

::ba dum bum pssshhhhh!!!::

George
Member
George
July 30, 2008 9:42 AM

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

George
Member
George
July 30, 2008 9:44 AM

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

George
Member
George
July 30, 2008 9:47 AM

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”.

Andrew James
Member
July 30, 2008 12:55 PM
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… Read more »
Al Hall
Member
Al Hall
July 30, 2008 10:06 AM

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”… wink
I know, I know…

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