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Thread: Discussion: Eclectic Group Of Galaxies ...

  1. #1
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    SUMMARY: While the Hubble Space Telescope infrared camera was imaging a piece of the sky as part of a scientific survey, operators decided to take a snapshot using its Advanced Camera for Surveys on an adjacent region - they weren't really looking at anything in particular. The image contains a jumble of unrelated galaxies, including a yellow spiral stretched by a galactic collision, a young blue galaxy with regions of starbirth, and some other small red galaxies. The blue arc in the middle of the image is actually a red galaxy which is serving as a gravitational lens to magnify a more distant blue galaxy.

    What do you think about this story? Post your comments below.

  2. #2
    StarLab Guest
    Hmm...makes for a nice screensaver.

  3. #3
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    Originally posted by StarLab@Jul 22 2004, 05:36 PM
    Hmm...makes for a nice screensaver.
    Right. not too much more than that. It's nice to see such a clean lensed galaxy. It's nice to see the galaxies imaged here, but we really don't know too much about them. We don't know how far away they are, etc. So yes, nice wallpaper until we study them more.
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  4. #4
    nebulae cloud Guest
    the hubble is fantastic, what great images it continues to produce. It's a terrible shame that it faces danger and the possibility that we might lose hubble soon

  5. #5
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    Gang,

    The story comments about the lensed galaxy containing hot young stars. C'mon, guys. That galaxy is 10 billion light years distant which means we are seeing it -- or at least its lens -- as it was 10 billion years ago. (For our international members, the American usage of 10 billion is 10,000,000,000.) Obviously it didn't spring into galaxyhood/star formation all at once so on top of that 10 billion there might be one or two additional billion years. So how can we call those stars "young?" They have to be among the oldest stars in our Universe. By now, were we able to see it up-close we might see that the whole galaxy is one large black hole with a few outlying stars still falling into it. Or that all the stars are now white dwarfs, brown dwarfs, black dwarfs, burned out cinders. . . .

    Donald

  6. #6
    StarLab Guest
    We call it "young" even after all these years for a few reasons:
    1- the galaxy won't fade away for billions of years anyways.
    2- the photons emanating from the galaxy that reached Hubble presently do not "age," therefore we call the location where the photons originated "young."

  7. #7
    Guest_Nick Guest
    I'm curious why the bright star shows difraction spikes. Does Hubble have a spider like a Newtonian telescope?

  8. #8
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    Can you imagine being on a planet in one of those galaxies and looking up in the sky to see two other galaxies without needing a telescope? We don't have any galaxies that close to us do we?

  9. #9
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    Originally posted by sarahnade_me@Jul 23 2004, 04:30 PM
    We don't have any galaxies that close to us do we?
    You can see the Large and Small Magelenic Clouds, and M31 without a telescope. the first two are pretty obvious.
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  10. #10
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    The blue arc in the middle of the image is actually a red galaxy which is serving as a gravitational lens to magnify a more distant blue galaxy.
    I read and reread this, tried to follow the article but I don't understand this.
    The blue arc is a gravitational lens, or the effect of a gravitational lensing of a blue backgound galaxy by a lensing red galaxy?? :huh: :huh:

  11. #11
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    Look for yourself:


    What the hubble web-site description say is:
    the most peculiar-looking galaxy of the bunch – the dramatic blue arc in the center of the photo — is actually an optical illusion. The blue arc is an image of a distant galaxy that has been smeared into the odd shape by a phenomenon called gravitational lensing. This "funhouse- mirror effect" occurs when light from a distant object is bent and stretched by the mass of an intervening object. In this case the gravitational lens, or intervening object, is a red elliptical galaxy nearly 6 billion light-years from Earth. The red color suggests that the galaxy contains older, cooler stars.

    The distant object whose image is smeared into the long blue arc is about 10 billion light-years away. This ancient galaxy existed just a few billion years after the Big Bang, when the universe was about a quarter of its present age. The blue color indicates that the galaxy contains hot, young stars.
    This means that the blue arc is hard Ultra-violet [Lyman-Alpha] light red-shifted down to look blue.
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  12. #12
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    Thanks Antoniseb,

    The previous post was me btw, so if I understand correctly there is a young starforming galaxy, redshifted to blue, seen by lensing of a red galaxy (the orange one with the smaller companion, I guess) as an arc. Does it mean that we see the blue arc through the red galaxy, or is the blue image in front of the red galaxy?

    Cheers.

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    Originally posted by VanderL@Jul 25 2004, 10:52 AM
    Does it mean that we see the blue arc through the red galaxy, or is the blue image in front of the red galaxy?
    We see the blue arc through the red galaxy. Note that the orange-red galaxy [bluish if it wasn't red-shifted] is an elliptical galaxy, and so it doesn't have much dust or molecular cloud to interfere with the image of the blue galaxy behind it. I'm guessing that the blue arc is probably an edge-on view of a young spiral galaxy.
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  14. #14
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    Originally posted by fraser@Jul 22 2004, 05:36 PM
    including a yellow spiral stretched by a galactic collision
    Now wait a moment. I'm no physicist but... if the Universe came from a single point in space and exploded outwards, ie: the "Big Bang" theory, how can two galaxies possibly collide? In fact, if the Universe is truly expanding as we think, how can two different gravity wells (massive objects such as galaxies & black holes) ever come into contact at all?
    Is it because some objects are moving faster than others from the central point & "catching up"? If so, how did they get "left behind" & then accellerated? Does this mean that the Universe is expanding faster in some areas than others? Or am I completely off track?

  15. #15
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    Originally posted by Tyndall@Jul 27 2004, 02:00 AM
    if the Universe is truly expanding as we think, how can two different gravity wells (massive objects such as galaxies & black holes) ever come into contact at all?
    Hi Tyndall, welcome to the forum.

    There are at least two factors that permit galaxies to collide:
    1. The expansion of the universe is on a scale in which the self gravity of the members of a cluster of galaxies is greater than the local expansion. Clusters of galaxies have not been observed to collide with other clusters.
    2. When the plasma of the big bang cooled to a transparent gas 380,000 years after the big bang, it did soslightly unevenly, so that some areas were getting photon pressure, while others were not, causing the relative movement of material beyond mere expansion.
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  16. #16
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    Still, I think it is a fact that colliding galaxies were once regarded as rare events, while today we even think our galaxies are made up of building blocks that would by necessity have collided.

    Cheers.

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