Galaxy crash sparks biggest spiral

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

Related Stories

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."


More on This Story

Related Stories

The BBC is not responsible for the content of external Internet sites


This entry is now closed for comments

Jump to comments pagination
  • rate this

    Comment number 51.

    To look to the skies is to put all in perspective. As humans we become so entangled in the bramble bush of life that we forget to look up and see how big the forest we are in actually is.

    People should make the time to stop and think about this stuff which on the one hand is science for the intellect and on the other philosophy for the soul

  • rate this

    Comment number 50.

    26.Jocky B
    ,,, Just how do these galactic mash ups happen? Surely goes right against the Big Bang theory.

    Oh dear - you have them there. All that study and research gone to waste. You are a clever clogs.
    Here is a weak and pitiful attempt to cover up the truth :-)

  • rate this

    Comment number 49.

    26.Jocky B
    That's an intelligent question - don't know why some idiot marked your comment down.
    The reason is that matter is distributed throughout the universe in clumps and so you have "local groups" of galaxies that are quite close to each other. The gravitational force within these groups is sufficient for some galaxies that are close together to be drawn back together and crash.

  • rate this

    Comment number 48.

    Any chance the rabid atheists could stop frothing at the mouth and not post random anti-religious posts on every single commented thread out there? It never seems to happen the other way round, you don't see posts going "You're all going to burn unbeleivers", yet apparantly all religious people are closed-minded and full of hatred.

  • rate this

    Comment number 47.


    Because there is no evidence to suggest that there is a massive portion of us that we can't see or touch.

  • rate this

    Comment number 46.

    Fantastic. Love this. The universe is a wonderful place. Makes me wonder what else is out there!

  • rate this

    Comment number 45.

    Simply AMAZING!!!

  • rate this

    Comment number 44.

    Gosh, a giant Milky Way - the sweet you can eat between meals without ruining your appetite. Yummy!

  • rate this

    Comment number 43.

    @26 JockyB, imagine filling a balloon with flour, then blowing it up until it bursts. The flour doesnt scatter in a uniform way, and neither did the matter from the big bang. As matter has gravity, matter attracts other matter, and over time these galaxies were attracted together as they moved. The galaxies arent moving away from each other per se, just away from the "Centre" of the universe.

  • rate this

    Comment number 42.

    1 Minute ago

    Well said! This article give me back a faith in mankind that all the petty bickering takes away. Great work science!

  • rate this

    Comment number 41.

    @26. Jocky B

    This question came up in Stargazing Live. Brian Cox explained that although the universe is expanding as a whole, within that there are smaller (!) systems, for instance groups of galaxies held together by gravity. We are in a group of 5.

    within these groups there can be collisions, even though the group is expanding away from others.

    Basically, Galaxies behaving Badly

  • Comment number 40.

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

  • rate this

    Comment number 39.

    Funny to think that this galaxy is held together by masses and Forces that comprises 95% of Universe and we cannot see, commonly known as Dark Matter and Dark Energy. Instead of placing this new reality out there , could we put ourselves in this same picture and assume that there is a massive portion of us that we cannot see and touch ? If not, why ?

  • rate this

    Comment number 38.

    Could this be in the memory of Patrick Moore - The Patrick Moore Glalaxy, rather odd but very interesting!

    This is a really nice bit of news to end the week with; different, cool, wonderful, almost unimaginable. Nice choice for HYS

  • rate this

    Comment number 37.

    Multum in Pavo?

  • rate this

    Comment number 36.

    @26.Jocky B

    I believe it's because there is a fight between the expansion of the universe pulling them apart and the force of gravity pulling them together. If the galaxies start of pretty close together then gravity is generally the stronger and hence they are pulled into a collision.

  • rate this

    Comment number 35.

    In the midst of all the reports on wars, paediphiles, economic and social collapse and other doom and gloom stories it's nice to see one that raises the spirits and shows us mankind is working towards understanding existence and improving it rather than trying to tear it down.

  • rate this

    Comment number 34.

    What we know now, is little in comparison to what we will know in the future & so much of what we come to know we will be surprised at.

    The need to leave this planet in future guarantees exploration like never before, it will take many generations being born on spacecraft to reach anywhere else, explorers will be born in space & never know the earth

    Sad, short life means we will all miss it

  • rate this

    Comment number 33.

    It's global warming. There were no spiral galaxies before 1943.

  • rate this

    Comment number 32.

    Every time we look more deeply at the universe, it gets more and more interesting.

    What wonders are coming up next?

    Great credit goes to those who keep probing and working out new and better ways to look.


Page 29 of 31


More Science & Environment stories



Try our new site and tell us what you think. Learn more
Take me there

Copyright © 2015 BBC. The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.