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 351.

    If I missed something that big in my job I'd be sacked on the spot. Muppets.

  • rate this

    Comment number 350.


    The convergent / divergent speeds of of two objects don't affect the speed of light; only the physical separation at the time of the emission of the light.

    What changes is the wavelength, which gives rise to the term 'Red Shift': the wavelength stretches (making the light 'redder' as the objects diverge.

    It's the same thing with light as the Doppler Effect with sound.

  • rate this

    Comment number 349.

    I predict in 10-20 years we will find the extremities of our Universe.
    50-100 years later we detect the edges of other Universes.

    Also our Universe will stop expanding, start to contract, collapse in, and eventually "Big Bang x.0", like many times before.

  • rate this

    Comment number 348.

    It makes you wonder who the real fanatics are.
    No it doesn't.

    As far as i know, no secularist has ever murdered another secularist's daughter because they support accelerating universal expansion over deccelerating universal expansion.

    The zealots are the religious who kill each other, the rest of us, and use fear, threats, and violence to maintain their own power.

  • rate this

    Comment number 347.


    I suspect it's just a confusingly written report. The galaxy is 212 million light years away so we are seeing it as it was 212 million years ago, the collision happened another 130 million years previous to that.

  • rate this

    Comment number 346.

    We're just a clever ape in a spot of bother baby...

  • rate this

    Comment number 345.

    340. labenal
    You are effectively saying that the astophysicists have calculated that this galaxy is moving away from us at light speed - in which case, we'd never see it.
    of course we would. Light FROM the galaxy moves towards us at light speed . The fact the galaxy is moving away from us at a similar speed (It has to be slightly less than light speed) doesn't affect that.

  • rate this

    Comment number 344.

    Another classic example of so-called astronomers making stuff to please sci-fi nerds.

    We need to be concentrating on life on earth not on this rubbish. They should all be given community service or made to study dentistry.

  • rate this

    Comment number 343.

    #339 about £ on science and£ 0 on overseas(aid) lottery.we might start solving some problems then.

  • rate this

    Comment number 342.

    I fear on the discovery that we are not alone, it would fuel even more wars between religious groups and possibly create an interstellar war. Im pretty sure most governments would try and keep it as much of a secret as possible.Humans can be afraid of the unknown but the known could cause even more harm.

  • rate this

    Comment number 341.

    The science budget should be octrupled...humanity needs something to aim for which is external to the day to day money and power, resulting in the conflicts we focus on - what better way than driving science forwards, together, to understand the universe at large.

    Forget the iPhone 20, and Facebook 2025, why not land on Mars?

  • rate this

    Comment number 340.

    @317 I asked a similar question to @292 (@196). Yours is the first attempt at an answer I've seen, but I'm afraid it doesn't convince.

    You are effectively saying that the astophysicists have calculated that this galaxy is moving away from us at light speed - in which case, we'd never see it.

  • rate this

    Comment number 339.

    We are shutting schools, hospitals and cutting benefits for the most vulnerable; Spending billions on this useless science "

    In 2010, the public science budget was frozen at £4.6bn. At the same time, we spent £118bn on health, £114bn on pensions, £33bn on education and £43bn on defence. We spend £8.4bn on overseas aid.

  • rate this

    Comment number 338.


    Re : 301.RogerGod

    The guy has posted an intelligent question which is quite appropriate for someone with a basic knowledge of Astronomy. You should direct him to the answer rather than putting him down with sarcasm.

    301.RogerGod - see post 49 for your answer...

  • rate this

    Comment number 337.

    The universe is a large place indeed, and life is part of it, probably forming part of its information system. We will probably never know. Scale seems to be very important, as it is evident that limits are set as one moves from the quantum scale through to the scales of galaxies - but I suspect all aspects of its workings are significant. We are part of this and should not underestimate our role.

  • rate this

    Comment number 336.

    331. David H
    That's a bit unfair. A nice man from the Ministry called yesterday and asked if I, or any of immediate family, had any spare fireguards going.

  • rate this

    Comment number 335.

    289.spam spam spam spam - ".....hence we dont just have to get off this planet, but out of this galaxy at some future point........."

    But that is just so much wishful thinking, it'll never happen - the distance between us our nearest other star system is so immense it would take 1,000s of years at speed way above our capabilities to achive.....

  • rate this

    Comment number 334.

    316. Red Robbo
    "and there is no god?"

    That's right, there is NO GOD.

  • rate this

    Comment number 333.

    'How come you science and religious fanatics are so far behind the film makers?'

    Most of whos ideas are stolen from the great sci fi writers of the last century and turned into 'action' movies- Arthur C. Clarke, Issac Asimov, Ray Bradbury, Brian Aldiss, Stanslaw Lem.. etc etc. Great ideas people, thinkers and visionaries. Filmakers tend not to be.

  • rate this

    Comment number 332.

    Isn't it weird how everytime some scientific discovery is made a mob of secularist zealots use it, with Pavlovian predictability, to attack religion. It makes you wonder who the real fanatics are.

    I'm not at all religious btw.


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