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
    +2

    Comment number 391.

    @363 The reason we see what happened so far in the past is that the light takes a long time to reach us from very distant events.
    What the red/blue shift does is it tells us how old the light is when it reaches us, so we know how long ago the event happened (the degree to which red and blue light are out of step). Its called the Doppler Shift - same effect with sound when a vehicle's siren passes.

  • Comment number 390.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • rate this
    +6

    Comment number 389.

    @375 "We need to worry about what's happening on earth, not looking for single celled amoebas on mars. Let's deal with MS, Parkinson's, polio and AIDS"

    We can multi-task you you know, there are quite a lot of humans on this planet capable of sorting all that stuff out as well. If you want to read about the politicians conning us then check out www.duhstatetheobvious.co.uk

  • rate this
    +5

    Comment number 388.

    How come the editors picks have not been updated for 3 hours, does this mean we have covered the whole of this subject? or has he gone for an executive liquid lunch since his last upload.

  • Comment number 387.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • rate this
    0

    Comment number 386.

    Time travel is possible. We are all, in effect, time travellers, but on a very miniscule scale we do not comprehend it. If a person is sat down and another person is walking their time is slower than the person sitting. The faster you go, the slower the time. Going back in time is a different question. Begs the question, go forwards how do you get back

  • rate this
    -2

    Comment number 385.

    Much of our understanding of the universe at large scale rests on Einstein's theories of special and general relativity. They are fundamental to our understanding of space-time, galaxy-level gravity and speeds comparable to c; and, thereby, to galactic collisions.

    Interesting that many equate theism with stupidity and irrationality, when Einstein was a theist whose name is synomous with genius.

  • rate this
    +1

    Comment number 384.

    376.SillyEnglandDotCom
    Just now
    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!

    +++

    It's tighter than that, more like 16 per m^2 or the area of an A4 sheet each.

  • rate this
    +4

    Comment number 383.

    368.Little_Old_Me
    I am also well informed about the basic fundamentals of physics

    1) Fundamentals are constantly redefined over time as new advances are made. It is arrogant to dismiss a possibility completely - a good scientist remains open minded.
    2) Even if faster than light travel isn't possible, as speeds improve we may gradually colonise star by star using "generation starships"

  • rate this
    +1

    Comment number 382.

    @368 We can't do it 'yet'. We know what we need to do to travel FTL and we know how to do it. We just don't have the technology or equipment to do it, 'yet'.

  • rate this
    +11

    Comment number 381.

    375. Binbartos
    We need to worry about what's happening on earth, not looking for single celled amoebas on mars. Let's deal with MS, Parkinson's, polio and AIDS
    -
    Polio is beaten apart from a few religious nuts in Pakistan. I'd laugh myself silly if the martian amoeba secreted an anti-HIV agent in the same way penicillin mould secretes an anti-bacterial on earth though.

  • rate this
    0

    Comment number 380.

    I'm a non-believer and am often confused about why people with faith do not see scientific discovery in a good light.
    With every new discovery I've seen recently , created are many more unanswered and potentially unanswerable questions?
    For those with faith, why does this not enhance the belief of a greater unknown force?

  • rate this
    +2

    Comment number 379.

    @363: labenal

    The expansion of the universe not only stretches light as it travels, it also increases the distance in front of it and behind it. Consequently light might travel for 130m years and end up 212m light-years away from where it started. Imagine crossing the Atlantic on a ship while somebody unfairly moves America further away...

  • rate this
    +11

    Comment number 378.

    @217.Donkzilla
    ''...Therefore our minds' eyes are faster than the speed of light.
    God 1 - 0 Science''

    Didn't know the ability to see and comprehend distance was the missing link to prove God and denounce Science. I always thought it had more to do with a persons faith, and the ability to prove things through evidence!
    Science 1 - 0 Very poor preacher

  • rate this
    +6

    Comment number 377.

    335.Little_Old_Me
    But that is just so much wishful thinking, it'll never happen - the distance between us our nearest other star system is so immense

    +
    Our present existance is due to so much wishful thinking, flying, going to moon, sending craft to other planets, ALL previously impossible.

    Time changes so much & so much changes in time, human survival/existance can never afford defeatism

  • rate this
    +1

    Comment number 376.

    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!

  • rate this
    -12

    Comment number 375.

    I'd rather comment on MP's wanting a 33% pay rise (all in it together...) or tony blair making million upon million from killing 800000 Iraqis, ruining the parliment and letting in millions of people in to our country, what... To drive vans??? We need to worry about what's happening on earth, not looking for single celled amoebas on mars. Let's deal with MS, Parkinson's, polio and AIDS

  • Comment number 374.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • rate this
    +3

    Comment number 373.

    336.paulmerhaba
    6 Minutes ago
    331. David H
    JUST NOW
    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.
    ~~~
    They only want the Chocolate variety, so they can blame it on somebody else.

  • rate this
    +7

    Comment number 372.

    359. mrwobbles
    "Prove it....As a scientist the most you can say is "I have no evidence.""

    No. The most I can say is that the concept of a "God" dates back to when humans could not understand the natural phenomena which they experienced and so assumed there must be some greater being behind it all.

    Oh, and I'm not a scientist. I don't know where you got that idea from!

 

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