“They will crash into each other in a few million years”

NGC 6240

As the NASA caption to the larger image says, “This [wondrous] image of a pair of colliding galaxies called NGC 6240 shows them in a rare, short-lived phase of their evolution just before they merge into a single, larger galaxy.” The image was constructed from infrared light taken by Spitzer’s infrared array camera showing cold dust and radiation from star formation; visible light from Hubble (green and blue) showing hot gas and stars. Image credit: NASA/JPL-Caltech/STScI-ESA. From the NASA press release

The blob-like shape of the galaxy is due to the sustained violence of the collision. Streams of millions of stars are being ripped off the galaxy, forming wispy “tidal tails” that lead off NGC 6240 in several directions. But things are about to get even more violent as the main event approaches and the two galactic cores meld into one. In the center of NGC 6240, the two black holes in the cores will whip up a frenzy of radiation as they careen towards one another head-on, likely transforming the galaxy into a monster known as an ultra-luminous infrared galaxy, thousands of times as bright in infrared as our Milky Way.

But Don’t Panic! From the same NASA press release

The galactic cores are in a single, tangled galaxy called NGC 6240, located 400-million light years away in the constellation Ophiuchus. Millions of years ago, each core was the dense center of its own galaxy before the two galaxies collided and ripped each other apart. Now, these cores are approaching each other at tremendous speeds and preparing for the final cataclysmic collision.

They will crash into each other in a few million years, a relatively short period on a galactic timescale.

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  • Seymour Major


    I’m trying to read into your post the angle on Northern Ireland politics and culture.

    Is this the St. Andrews agreement being represented in outer space? Could it be that Sinn Fein and the DUP will merge into a new political party (the OTDP – Ourselves together Democratic Party)?

  • Pete Baker

    “I’m trying to read into your post the angle on Northern Ireland politics and culture.”

    Don’t, Seymour.

    It’s not there.

  • The Reincarnation of Paul Revere’s Horse

    Our own galaxy and the Andromeda galaxy are doing the same from what I’ve read. It will take about 4 billion years though, enough time for me to fit in my holiday to France and a few other things.

    If it will destroy us or not is another matter but it’s bound to look stunning and who knows, with a bit of reform in the health department I could be there to see it.

  • Greenflag

    But how can ‘galaxies ‘ collide with each other ?
    Did I not read somewhere that galaxies are moving away from each other at ever increasing speeds ? Considering all galaxies originate from the big bang then if there are galactic collisions then could this be evidence that the known universe is beginning /has begun it’s long term theoretical contraction to the singularity ?

    Anyway whats happening to this Hadron collider and dark matter .These are important questions but perhaps not on this day ;)?

  • joeCanuck

    dark matter

    An inadvertent clue to the answer, Greenflag?

  • Comrade Stalin


    I think Mr Major was being humourous.

  • Devil Eire


    All large-scale structure in the universe (galaxies and their clusters) has its origin in density perturbations in the early universe. We can see these seeds of structure directly as variations in the Cosmic Microwave Background, the ‘afterglow of the Big Bang’.

    It’s correct to say that all galaxies are receding from each other according to Hubble’s Law (with a modern twist). But each galaxy has its own ‘peculiar velocity’ with respect to this ‘Hubble flow’. (Imagine two flies walking around on an expanding balloon.)

  • Greenflag

    Devil Eire ,

    Thanks for the heads up and brilliant name btw 😉 At least half my clan agree he was a bit of a devil .

    ‘Imagine two flies walking around on an expanding balloon’

    I’ll try 😉 But if they are to collide then they must ‘walk’ at different speeds or as you put it ‘peculiar velocity’

    Thanks for the link . Not much hope for our Virgo cluster then eh ?

  • Greenflag

    joe canuck ,

    Well spotted 😉 and it is indeed a dark matter or as Father Jack would say a very very very very very dark matter and unlikely ever to be an ecumenical one (matter );)

  • Devil Eire


    “But if they are to collide then they must ‘walk’ at different speeds or as you put it ‘peculiar velocity’”

    Well, they just need to have velocities which put them on intersecting paths, resulting in a collision or merger. Galaxies which are close enough to collide are probably gravitationally bound in the same supercluster. The peculiar velocities then dominate over the Hubble flow anyway. (Those flies are waltzing around faster than the balloon is expanding).

  • Greenflag

    Devil eire,

    ‘Those flies are waltzing around faster than the balloon is expanding). ‘

    As Father Dougal would have said -‘Brilliant’
    Or as Father Ted would have said

    ‘Those ‘big waltzing flies ‘ are near and can collide with each other whereas those ‘small waltzing flies’ are moving further away so they can’t collide with the big waltzers ‘;))

    Seriously – I noted your use of the word ‘probably’ gravitationnally bound . Using the expanding ‘balloon ‘ analogy with the galaxies ‘stuck’ to the outside skin of the balloon and said balloon expanding then there would have to be ‘peculiar’ velocities to have any collissions . Of course the analogy of the balloon may not be 100% correct and this ‘dark matter ‘ stuff is probably adding the necessary chaos to add to the colloidal chaos .

    The universe is even queerer than we can imagine is a line which some observer made .

    But thanks for the info -much appreciated .

  • Rory Carr

    I heard on the radio the other day a snippet that reported that new evidence suggested that the likliehood of there being water on Mars was even greater than before and that somehow that made it more important than ever that man travel to Mars.

    I simply don’t understand this reasoning and I was hoping that you, Pete, my Official Chief Scientific Advisor, might explain it.

    After all there probably is water to be found in Ballymena but you would never hear of anyone wanting to go there.

    Submit Word : “Girls”!

    The ghost of Father Jack is haunting this thread.