Galaxy crash sparks biggest spiral

VLT/Galex image of NGC 6872 Galex revealed a wealth of new stars at the galaxy's outer reaches

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Astronomers have spotted the largest known spiral galaxy - by accident.

A team was looking through data from the Galaxy Evolution Explorer (Galex) satellite for star-forming regions around a galaxy called NGC 6872.

But they were shocked to see a vast swathe of ultraviolet light from young stars, indicating that the galaxy is actually big enough to accommodate five of our Milky Way galaxies within it.

The find was reported at the American Astronomical Society meeting in the US.

NGC 6872, a galaxy about 212 million light-years away in the constellation Pavo, was already known to be among the largest spiral galaxies.

Near it sits a lens-shaped or lenticular galaxy called IC 4970, which appears to have crashed through the spiral in recent astronomical times.

Rafael Eufrasio of the Catholic University of America and Nasa's Goddard Space Flight Center and colleagues from the University of Sao Paulo in Brazil and the European Southern Observatory in Chile were interested in a number of regions away from the galaxy.

"I was not looking for the largest spiral - it just came as a gift," Mr Eufrasio told BBC News.

Galex - a space telescope designed to search for the ultraviolet light that newly born stars put out - hinted that NGC 6872 was made much larger in size by the collision.

The team went on to use data from a range of other telescopes including the Very Large Telescope, the Two Micron All-Sky Survey and the Spitzer space telescope - each of which sees in a particular set of colours, in turn evidencing stars of varying ages.

They found the youngest stars in the outer reaches of the galaxy's enormous spiral arms, getting progressively older toward the centre.

That suggests a wave of star formation that travelled down the arms, set off by the collision with IC 4970, with the newest stellar neighbourhoods pushing the galaxy into the top spot in terms of size.

"It's been known to be among the largest for two decades, but it's much larger than we thought," explained Mr Eufrasio.

"The galaxy that collided with the [central disc of NGC 6872] splashed stars all over the place - 500,000 light-years away."

A simulation of the galactic collision suggests it happened 130 million years ago A simulation of the galactic collision suggests it happened 130 million years prior to the situation we see today

Besides being one for the record books, NGC 6872 updates the catalogue of known galaxy smash-ups, demonstrating how dramatically galaxies can be changed and added to by collisions.

"It shows the evolution of galaxies in the larger context of the Universe - how the large galaxies we had before were accreted from small clumps in the early Universe," Mr Eufrasio said.

"We're just seeing one example of two interacting galaxies but in the past that happened much more often - that's how the big [spiral galaxy] discs we have were probably formed. Putting that in a larger context, it's a very cool system."


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  • rate this

    Comment number 411.


    The point I'm trying to make is that this story has nothing to do with religion but many secularists nevertheless insist on dragging religion into it. This is a frequent occurence. Instead of simply accepting science stories for what they are they immediately exploit them for a bit of gratuitous religion-bashing. This is the act of a zealot.

  • rate this

    Comment number 410.

    5 Minutes ago
    testing observational skills:

    God created the Earth and He created us.
    If he did, I hope he does a better job next time.
    Maybe he needs the "Idiot's Guide to Creation" available on Amazon

  • rate this

    Comment number 409.

    390. Howesyourview
    God created the Earth..... He will continue to hinder your investigations by creating false evidence (like galaxies and dinosaurs).
    Genesis 1:16 "God made two great lights--the greater light to govern the day and the lesser light to govern the night. He also made the stars"

    The galaxies are clusters of stars. You are SERIOUSLY confused about science AND your bible.

  • rate this

    Comment number 408.

    1 Hour ago
    1 Hour ago
    "Personally I think Richard Dawkins should be Prime Minister!"

    "... no he shouldn't. He's the kind of guy that tells his 3 year old grandchild that santa doesn't exist."
    To be fair he actually tells grown ups that Santa doesn't exist.

  • rate this

    Comment number 407.

    @395 "Is that based on the principles established by a certain Gene Roddenberry in the 1960s by any chance?" No, principally Einstein again although expanded upon.

  • rate this

    Comment number 406.

    @398. Raftafari1664

    Your observational skills are disappointing. If you had realised that in Editors pick's, my comment is entirely nothing to do with God and infact suggests that I do not believe in God might of led you to the conclusion that I was experimenting with the closed minds of the BBC commentors. I've concluded anything with the word God in it gets voted down. THINK OUTSIDE THE BOX!

  • rate this

    Comment number 405.

    "Did you know that you can fit the entire population of Earth onto the Isle of Wight, assuming that nine humans stand on one square metre, which is possible...I've tried. Now THAT is interesting!"

    Not if they are Americans.

  • rate this

    Comment number 404.


    No wonder the public get turned off science with people like you about ! An interested person posts a reasonable question on here (several others raised that same question too !) and you mock his lack of knowledge. In the same amount of time you took composing your unhelpful message, you COULD have just answered his question !

  • rate this

    Comment number 403.

    390. Howesyourview
    testing observational skills:

    God created the Earth and He created us. Why are you lot so content in trying to disprove His work. He will continue to hinder your investigations by creating false evidence (like galaxies and dinosaurs).

    Why He, men got to pee standing up but women got the multiple orgasms.

  • rate this

    Comment number 402.

    When our milky way hits the incoming Andromeda head on...not two stars will collide to each other...such are the distances and such is the size...if only was could live for billions of years to see it...our atoms would however hang on till take solace...we will observe albeit quantamly!:)

  • rate this

    Comment number 401.

    349.David H
    ...Also our Universe will stop expanding, start to contract, collapse in, and eventually "Big Bang x.0", like many times before..
    I always thought this but the latest is that we will continue to expand and disperse until verything is cold and dead.

    hopefully by then we'll be mixing it up with the rest of the universes and civilisations out there!!

  • rate this

    Comment number 400.

    #390 It so happens I'm a believer. May I take this opportunity to challenge your aggresive anti-science post? What are you really trying to achieve with your post, which will only make the scientists laugh with sheer derision?
    Why can't you admire the beauty of creation without taking a bite out of the scientists? They are only doing their best with the evidence as they understand it.

  • rate this

    Comment number 399.

    385 continued

    Einstein, of course, was much too intelligent to ever make typos.

    Unlike the impression given by some posters, I am fully aware that I am very, very far from his level:)

  • rate this

    Comment number 398.

    Howesyourview, waiting for you to come down off those mushrooms... which don't actually exist. Did you eat them or not? Did you eat nothing? Is there anything? Blah blah blah.

  • rate this

    Comment number 397.

    @374 chrislabiff. It's possible for the BEEB to run more than one news story you know!

  • rate this

    Comment number 396.

    Take the Higgs Boson. The theory says that elementary particles, Quarks, Electrons and the like, found inside Atoms get their mass from an invisible field that stretches through all of space. Without something to give particles mass, there would be no stars, planets or life as we no essence, its why we're here. Did God create that stand alone Singularity, in which the whole shebang exited?

  • rate this

    Comment number 395.

    We know what we need to do to travel FTL and we know how to do it."

    Is that based on the principles established by a certain Gene Roddenberry in the 1960s by any chance? I think the alternative proposals of EE "Doc" Smith are worthy of investigation too, though.

  • rate this

    Comment number 394.

    It's fascinating and beautiful. I love Astronomers and Astro Physicists work and their manifestation of consciousness if only for the incredible pictures and innovations in Technology it produces. In my opinion however they research and investigate 'light', what already has manifested. Hard to grasp for many is the 'observer collapses the wavefunction' in consciousness. Black matter is no 'matter'

  • rate this

    Comment number 393.

    " anyone that thinks Sharia law is a good thing also wants to drag mankind back to the dark ages.
    When that stupidity is removed we may be able to move forward as a species."

    Regrettably there seems no survival advantage in ditching this stupidity. That particular one will end soon enough but we have evolved to find/learn patterns and if they aren't there. we make them up.

  • rate this

    Comment number 392.

    347. Rate this comment negatively - It's not really a mistake, just that there's two different ways you can look at it. Whilst saying one galaxy is several hundered million years "in the past" is a nice concept to explain to people, it doesn't make much sense to an Earthbound observer, as as far as it's physical effect on us, it's in the same time scale.
    "Light cones" explain this well.


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