Hold on tight: in 4 billion years, we're due for a galactic collision!

By Phil Plait | May 31, 2012 1:01 pm

The galaxy we live in, the Milky Way, is a large spiral galaxy that lives in a small cluster of other galaxies called the Local Group. The other big member is the Andromeda galaxy, located about 2.5 million light years away. That’s a long way off, but we’ve known for a long time that Andromeda is heading more or less toward us at a speed of roughly 100 km/sec (60 miles/second).

The question is, is it headed directly at us, or does it have some "sideways" motion and will miss us? New results announced today by astronomers using Hubble show that — gulp! — Andromeda is headed right down our throats!

But don’t panic. It won’t happen for nearly 4 billion years.

This is a pretty cool result. They used Hubble to look at stars in Andromeda’s halo, the extended fuzzy region outside the main body of the galaxy. By very carefully measuring the positions of the stars over seven years, they could directly measure the motion of those stars. Extrapolating that into the future has allowed the motion of the Andromeda galaxy itself to be determined for the first time.

So what’s going to happen?

First, watch this awesome video of the collision based on the observations:

So here are the details:


Over the next few billion years, Andromeda — currently a barely naked-eye object in the northern sky — will grow larger as it approaches. In just under 4 billion years, the mutual gravity from the two galaxies will start to play havoc on each other. The Milky Way and Andromeda are about the same mass, so the effects they will have on each other will be profound. Stars on the outskirts of both galaxies will be drawn out, and long tails or streamers of stars and gas will be flung out.

Then, over a hundred or so million years, the galaxies will physically collide. Stars are small and so far apart on galactic scales that the odds of two stars colliding (or even getting close enough to affect each other or any planets) are actually incredibly small. But gas clouds are huge, light years across, so head-on collisions between them is inevitable. They’ll crash into each other, collapsing, and furiously form new stars. These stars will light up the gas, and from a distance the two galaxies will be seen have long strings of fiercely glowing red gas along their arms, like the Antenna galaxies, shown here.

The two galaxies will probably pass right through each other, pulling apart even as chaos reigns inside each. But the pull of gravity will not be denied. They’ll slow as they draw apart, eventually stop, and fall back in to each other. At that point they’ll merge, becoming a single, larger galaxy. It will probably be an elliptical galaxy, a big fuzzy cotton ball, as opposed to the spiral that each galaxy is now. That will take about two billion years after the initial collision, or six billion years from now.

Interestingly, the Sun will still be around then. It’ll be different, having used up most of its nuclear fuel, and on its way to becoming a red giant. But it’s possible the Earth and other planets will still exist! So it’s possible someone (maybe not resembling humans too much, but still) may yet be around to watch this event unfold.

The Sun’s orbit around the galaxy will change, though. Right now we orbit the Milky Way’s center in a roughly circular path, taking over 200 million years to complete one orbit. According to the models the astronomers developed using the Hubble observations, during the collision the Sun will be flung into a looping elliptical orbit around the new galaxy’s center, taking it farther out than we are now. That may be a good thing: both the Milky Way and Andromeda have supermassive black holes in their cores, and these black holes will merge eventually as well. It’s unclear what will happen when this occurs (though we may become an active galaxy, spewing out huge amounts of energy), but I suspect it’s best to be as far from that as possible when it does!

These new results make me pretty happy. We knew that a collision was inevitable, but the timing has always been a question. In my book Death from the Skies! I wrote a chapter on this event, but based on what was known at the time (just a few years ago!) it was supposed to happen in 1-2 billion years. These new results double that to 4 billion, which means I have a firmer number to quote. Moreover, we didn’t know if it would be a glancing blow at first or a head-on collision, and it looks now like it’s headed right at us.

And while this sounds like a catastrophic event — because it is — we have some breathing room. Four billion years is long enough, I should think, for anyone.

Image credit: Hubble artwork: NASA, ESA, Z. Levay and R. van der Marel (STScI), T. Hallas, and A. Mellinger; Antenna galaxies: Image credits: Davide de Martin, NASA.


Related Posts:

The cold arms and hot, hot heart of the fuzzy maiden
Ten things you don’t know about the Milky Way Galaxy
Andromeda’s majestic spray of billions of hot stars
The start of a long, long dance
Galactic friends and neighbors
Andromeda: born out of a massive collision?

Comments (90)

  1. Hi Phil- You might want to check your conversion in the first paragraph, 50km/sec is NOT 80mi/sec! Good post otherwise!
    -Dean

  2. Kullat Nunu

    Think about that. Our planet and the Sun will probably outlive our galaxy.

  3. Ok, we have a few billion years to hammer out the important matters: What would we call this new galaxy? I’m lobbying for Mildromeda Way.

  4. Zach

    So who is to blame for this? When filling out the insurance report 5 billion years from now, who is at fault? Are we going to be colliding with Andromeda, or are they colliding with us?

  5. Lorne Black

    At the end of para1 I think you have transposed the miles & kilometres. Still, it would be a hell of a sight to witness.

  6. Dean (1): D’oh! Thanks. I grabbed the wrong numbers. I fixed it.

  7. That video rates 9 “wows” on my completely arbitrary “wow” scale!

  8. Crudely Wrott

    50 km/sec = 80 m/sec?

    Looks like unexpected effects of impending collision are already manifest!

  9. Other Paul

    @TechyDad – I’ve never considered ‘Milky Way’ an actual name but more of a naively descriptive penenym. Though I do like your rather lovely suggestion, regardless.

    Much like ‘Earth’ has just been adopted from the word for the stuff on/of the ground that plants grow out of and dead animals merge into. Terra is ‘posher’ – and feels ‘namier’ – but it’s still just the same word from a different language spoken by a bunch of long dead monkeys.

    It’s about time we gave our home galaxy a proper name.

    Whilst on the subject, presumably – in the Messier Catalog – our galaxy’s designation would be M0, or has some other object nabbed that honour?

  10. Frank

    Nevermind, fixed already I see :)

    —–
    Hi,

    I think you made a little number switch. 50km != 80 miles, however 50 miles is about 80 kilometers though ;)

    Greetings from .nl
    Frank

  11. James

    Why did they turn from blue to brown?

  12. NAW

    Am I the only one that had a quick chuckle to them-self imaging the silhouette of a guy and a couple of robots in that first image.

  13. Frabjus Day

    Phil, it looks like you got the miles & kilometers switched (“50 km/sec (80 miles/second)”, para. 1)

  14. PK

    Neat article, but I think you got your conversion mixed up. 50 km/sec does not equal 80 m/sec. 80 km/sec works out to be just under 50 m/sec.

  15. KC

    Our home galaxy already has a name – what’s wrong with Milky Way? It has served as nom de plume for two millenia.

    No the Milky Way is not in the Messier catalog because at the time the concept of a galaxy did not even exist.

  16. Chris

    @10 James
    My guess is it shows the age of the stars. Young stars are blue, old stars are red.

    I’ve also had an issue with the name Milky Way. It sounds too simple. Our stars have cool names like Zubenelgenubi. Also how do you think the aliens will react when we tell them the galaxy was named after a candy bar?

  17. Ragdus

    Forgive me if this is a dumb question, but how well have we calculated the expansion rate of the universe? Andromeda will certainly have less space to traverse each and every day to get here, but also less expanding space, which should make it seem like its speeding up. Coupled with the increase in speed as each galaxy nears the center of the others gravity well, we’ll see a hell of a velocity increase, right? I’m assuming those things were factored in, but I’m just wondering how well we know those numbers…

  18. Bjoern

    Shouldn’t both galaxies become deformed (due to tidal forces) well before the collision? I don’t see that in the video…?

  19. Ivan Pantaleão

    @9-Other Paul: last time I checked Portuguese was STILL a very popular and alive language; so, IMHO, “Terra” is just fine! ;) Just saying… :p

  20. Chris Winter

    Well, in the best of all possible futures, we or our descendents will be able to manage that collision. There seems to be enough lead time to develop the technology (both quantity and quality.)

    OT: Scientific American this month has a fascinating article on supernovae triggered by antimatter. Perhaps the BA could do a post on this.

  21. kat wagner

    I love the name Milky Way, emphasis on Way. Just looking up at it every time I take the puppy outside at night, why, it’s a river of stars! And I thought the candy bar was named after our galaxy. And I thought Native Americans thought up the name. The Milky Way – a River of Stars. Just amazing.

  22. Bjoern

    @Ragdus: On such relatively small scales (some million light years), the expansion of the universe is negligible; it only becomes important on larger scales (several tens of millions of light years).

  23. velescu octavian

    vorbim de 4 miliarde de ani ca si cum as fi vreo 4 ani,e atit de mult timp incit nici nu ar trebui abordat acest subiect.Atit de multe presupuneri,atitea teorii se scrie,se vorbeste,dar certitudini nimic,STIMATI ASTRONOMI,hai sa ne lepadam de tot ce se cosidera adevar in UNIVERS si sa privim lucrurile din alt punct de vedere,sa cautam legile adevarate care guverneaza UNIVERSUL si atunci vom putea calatori in spatiu.SUCCES

  24. Ron Sharp

    Quick! Hit the brakes! Brace for impact!

    (This thing has airbags, right?)

  25. Keith Thompson

    We discussed this on the Astronomy StackExchange site, which has since been merged into the Physics site, http://physics.stackexchange.com/

    http://physics.stackexchange.com/q/26745/5646

  26. Jay

    @20 – Chris: Four billion years should be long enough to use a gravity tug to pull the Milky Way out of the line of fire. We just need to figure out a way to attach an ion drive to a black hole…

  27. Ron Barnes

    Its impossible to tell from the video, but it looks like the Triangulum Galaxy will pass close by the merger. Will it continue past or will it eventually be sucked in?

  28. Keith Thompson

    @25 – Jay: Attaching an ion drive to a black hole is easy. Getting it to work after it’s attached is the hard part.

  29. Keith Bowden

    Look out, it’s coming right for us!

    **blam! blam! blam!**

  30. Edward Gioja

    While it will be 4 billion years before they collide, at what point will we (well, the future ‘we’) start feeling the gravitational effects?

  31. chief

    Guess we will be the proud owners of a super massive black hole once everything settles down.

    Really wish we could speed things up and have a front seat view of the galaxy overhead when it is from horizon to horizon.

  32. Maria Aulisio

    I love the name milky way too, besides I’m sure the extraterrestrials have their own names for all the planets and galaxy’s…lol

  33. Tony Mach

    600 million years from now:

    As weathering of Earth’s surfaces increases with the Sun’s luminosity, carbon dioxide levels in its atmosphere decrease. By this time, they will fall to the point at which C3 photosynthesis is no longer possible. All plants which utilize C3 photosynthesis (~99 percent of species) will die.
    http://en.wikipedia.org/wiki/Timeline_of_the_far_future#Future_of_the_Earth.2C_the_Solar_System_and_the_Universe

  34. OtherRob

    I notice that the Triangulum galaxy comes out of this looking to be in rather good shape. Has anyone checked on what it’s been up to these last few billion years? Hmmm? I say it’s mighty suspicious…

  35. BeerMe

    @Chris & kat wagner,

    Yeah, the candy bar was certainly named after our home galaxy, but no it wasn’t the Native Americans who gave us the name. It looks milky, and all the way back in Hellenistic Greece they were using that term (though in their language) to describe it. So it entered Western culture long before Columbus or Mars (the candy corporation, not the planet).

  36. Other Paul

    @KC I can see why you thought that’s what I was asking, but I did ask if M0 would be its designator – if it were in the catalog. Though in any case the reason for its exclusion couldn’t be the one you suggest since there are galactic Messier objects entered in there after the concept of galaxies was known.

    @Ivan Pantaleão The fact that terra remains extant in contemporary languages doesn’t mean that the name didn’t come from Latin, which is all I was saying!

    @kat wagner Yes, the candy bar came later. I believe @Chris was joking. But I see you like the ‘Way’ bit. Are you suggesting some kind of name based on a Tao of Milkiness? I could go for that. But I’d still prefer something that sounded less like a name a child invented!

    @Keith Bowden – Pew, Pew, Pew.

  37. Daniel J. Andrews

    I also had a questions about Triangulum. It didn’t appear to be distorted and didn’t appear to be falling into the gravity well of the combined galaxies. In fact, it didn’t appear to be affected by the gravity that pulling Andromeda and the Milky Way back together after the collision when they passed through one another. Is that because it is too far away and the perspective just makes it look like it would be affected?

  38. Trucker Doug

    This collision is a major plot point in Alastair Reynolds’ “Revelation Space” series. Long story short, with minimal spoilers, long before life arose on Earth aliens realized that when the Big Splat happens species with interstellar capability will engage in catastrophic war to secure the best positions, reducing the ability to reduce the effects of the collision. So there exists Inhibitors, machines that roam the galaxy looking for emergent interstellar civilizations and squishing them. At the time of the novels, humanity has had near-C interstellar travel for about three centuries…

    Reynolds is a great author who manages to write epic space opera while following the laws of physics (mostly.) One of his books features a chase scene that takes 60,000 years.

  39. Pete Jackson

    I think we need to ask Congress for some funding on a preventative scheme. How about building giant X-ray lasers in orbit that shoot a powerful beam at each star of M31 in turn. It will take a while, but gradually we should be able to reverse the motion of M31 towards the Milky Way and send it on its merry way.

    Don’t call this ridiculous; wasn’t a lot of money spent in the 80s on some sort of scheme like this…

  40. Scott

    Like several other folks, I noticed that Triangulum seems to be out of play through this event. How is that possible? And why do Andromeda and Triangulum appear to pitch and roll during the approach while Milky Way appears to stay at a constant level?

  41. All that stardust!
    The stars are just glittering dust floating around in clumps.

    @Tony Mach – we can fix that, even now test runs of global warming do the job nicely. :)

  42. Messier Tidy Upper

    Interestingly, the Sun will still be around then. It’ll be different, having used up most of its nuclear fuel, and on its way to becoming a red giant. But it’s possible the Earth and other planets will still exist! So it’s possible someone (maybe not resembling humans too much, but still) may yet be around to watch this event unfold.

    From my understanding the Earth has a lot less time than this as a habitable planet.

    Our Sun is gradually becoming more luminous and hotter as it ages and in only a billion or so years the Habitable Zone will shift so that Earth, currently near its inner edge falls into the too-hot region and is hit by the same runaway greenhouse effect that had made Venus the highly hostile hellplanet we know today.

    So with or without our help in setting off such a runaway greenhouse effect – and climatically we are in serious trouble now we just mostly don’t realise it yet because of the thermal climate inertia – Earth’s future is going to be Venus-like sooner than most of us think. Long before the MIlky Way-M31 collision.

    So, sorry BA, but nope, not likely at all for Earth anyhow!

    Of course, that assumes we don’t take steps to move Earth’s orbit outwards out of the way or resettle on Mars, Titan, Pluto and elsewhere! ;-)

  43. Messier Tidy Upper

    @41. Scott Says:

    Like several other folks, I noticed that Triangulum seems to be out of play through this event. How is that possible? And why do Andromeda and Triangulum appear to pitch and roll during the approach while Milky Way appears to stay at a constant level?

    I’m guessing that would be because M33 -Triangulum – lies in the background and is passing behind the colliding galaxies.

    Be intresting to see what happens to the Magellanic clouds and M32 and M110 in this scenario – although I guess they may have already merged with us and Andromeda respectively?

    @19. Ivan Pantaleão Says:

    @9-Other Paul: last time I checked Portuguese was STILL a very popular and alive language; so, IMHO, “Terra” is just fine! Just saying… :p

    Terra i s earth inPortugese? Neat – that’s something new I’ve learnt for today! I thought it wa sfurtehr from Latin than Italian and French and Spanish (the “romance languages” family) though? Is the ‘Moon’ called Luna in Portugese too – and what’s Pluto?

    ***

    Our Sun’s brightness is gradually increasing by about 10 % every billion years.
    – McNab, David & Younger, James, ‘The Planets’, BBC Worldwide,1999. & “The Planets” final episode – ‘Destiny” , BBC TV, screened circa 1995-2005. (?)

  44. Messier Tidy Upper

    @3. TechyDad :

    Ok, we have a few billion years to hammer out the important matters: What would we call this new galaxy? I’m lobbying for Mildromeda Way.

    I believe the commonly accepted post-merger designation for the combined MilkyWay – M31 elliptical galaxy to be – and one I think works well – is Milkomeda! ;-)

  45. Messier Tidy Upper

    For one plan to gradually shift the Earth’s orbit with repeated asteroid passes see :

    http://www.space.com/107-life-earth-escape-swelling-sun.html

    Whilst one item on Earth’s future here:

    http://carlkop.home.xs4all.nl/toast.html

    Gives us only another half a billion years of habitability left.

    With this link :

    http://www.lcas-astronomy.org/articles/display.php?filename=what_the_future_holds_for_the_earth_and_the_sun&category=the_planets

    Providing a second opinion also none too good a future.

  46. CR

    Strange, for many years (since I was a young child, nearly four decades ago), I knew that the Sun would eventually swell up & swallow Earth before burning out, say in about 5 billion years. That knowledge is so ingrained in me, I barely give it a second though.

    A few years ago, I started hearing about the upcomoing Milky Way/Andromeda collision, but for some reason thought we had about 7 billion years before the main collision happened. (Perhaps the first time I heard of it, that time frame was the best estimate we had, and it just ‘stuck’ with me ever since.)

    Now, it seems that our solar system is likely to outlive the two galaxies?!
    That. Is. Freaky.
    I always knew that stars come and go with relative quickness, but in spite of evidence of colliding galaxies, I always viewed galaxies as generally more stable and long-lived. Never thought it would happen here so soon!

    To quote a character in a very non-scientific movie, “I’m freaking out, man!” My reaction IS in a good way, though… go, science! And once my subconcsious mind wraps itself around the whole concept, I’ll just accept it and move on, hoping that I live long enough to be able to say “See that galaxy up there? When I was a kid, it was a lot smaller ’cause it was so much farther away…” (OK, I doubt I’ll make it to such a ripe old age, but it’s fun to imagine!)

  47. DLC

    See, it’s the Quickening Galactic Convergence Global Consciousness Collision Conspiracy.
    Fortunately, Oprah Winfrey will find a way to use The Secret to change the Andromeda galaxy’s course, so it will miss us on December 4,000,002,012

  48. Roger Wilco

    @36 BeerME: It looks milky, and all the way back in Hellenistic Greece they were using that term (though in their language) to describe it.

    And that word in “their language” just happened to be galaxias — “galaxy”. Two names for the price of one!

  49. Wilfried

    We all know that the actual shape of the Andromeda galaxy is not what we see in the pictures. If the light from a star on the nearby edge was emitted at time t, then the light from a star on the opposite edge was emitted at t-40000 years or so. But with the speed of motion now known it should be possible to compute a picture for the entire galaxy at time t! Would such a task not qualify for a diploma’s thesis?

  50. Mathias R.

    @36 BeerME: The hellenistic greek word for the milky way was ‘galaxias’ (or something to that effect. Which, essentially, means ‘milky way.
    The romans called it, appropriately, ‘via lactea’, or the milk road.

    To get a bit more deviant view, in Swedish the milky way is called ‘vintergatan’, which roughly translates to ‘winter road’. Not surprising, considering its visibility would be way higher during the long winter nights in the northern latitudes as opposed to a summer where the sun barely settles. :)

  51. George Kopeliadis

    Actualy “galaxias” in greek mean just “milky”. The complete name was “galaxias kyklos” that mean “milky circle”

  52. Satan Claws

    Visual example using Graphics Processing Unit (GPU):
    http://www.youtube.com/watch?v=aByz-mxOXJM#t=3m30s

    (Sorry about spamming with a proprietary product, but it seems interesting enough to watch.)

  53. pavium

    “So it’s possible someone (maybe not resembling humans too much, but still) may yet be around to watch this event unfold.”

    I don’t know … seeing it ‘unfold’ would take several times more than the lifespan of any one species. They’ll each see it like we do: as a (frozen) snapshot.

    Nevertheless, when this story becomes more widely known, you’ll be fielding questions from panicky people worried that the sky really is falling.

  54. Peter Davey

    This rather reminds me of the joke about the two scientists:

    The first one says: “We now have evidence suggesting that the Universe will end in approximately four billions years.”

    The second scientist jumps up in horror: “That’s absolutely dreadful!”

    The first scientist, puzzled, says: “Why are you so shocked about something that is four billion years away?”

    The second sinks back in his seat, mopping his brow: “Thank Heavens for that. For a moment there, I’d thought that you’d said four million years.”

    I suppose that it’s all a matter of perspective.

  55. Poul-Henning Kamp

    And as always there is an appropriate HHGTTG quote:

    “Last orders…”

    :-)

  56. Angelo Franco

    @44. Messier Tidy Upper Says:

    Terra i s earth inPortugese? Neat – that’s something new I’ve learnt for today! I thought it wa sfurtehr from Latin than Italian and French and Spanish (the “romance languages” family) though? Is the ‘Moon’ called Luna in Portugese too – and what’s Pluto?

    Moon – Lua
    Pluto – Plutão

  57. Brandon J G

    I feel sorry for those who are excited about this as if it is something that was just discovered. This has been known for quite some time.

  58. James

    (44) Messier Tidy Upper already raised the subject of the fates M101 and the Magellanic clouds and other large satellite galaxies. I’m wondering what happens to all the the other galactic halo objects, like globular clusters and LSB galaxies, that will be caught in the gravitational crossfire long before the spiral arms start to wrestle. Wouldn’t they slurp up a lot of the ejected gas and dust and spark up into galaxies in their own rights?

    For that matter, the Local Group is currently dominated by the two big spirals; wouldn’t the massive new elliptical just overwhelm and slurp its way through a buffet of M33 and the other survivors of the the big gulp?

  59. Messier Tidy Upper

    @ 57. Angelo Franco : Aww, so close! Thanks. :-)

    @15. KC : “No the Milky Way is not in the Messier catalog because at the time the concept of a galaxy did not even exist.”

    Plus even if it had, it is pretty hard to confuse the Milky Way with a comet even in telescopes of that era! ;-)

    Mind you hard to see how anyone could confuse the Plieades or the Wild Duck cluster with a comet either!

    (NB. Charles Messier orginally developed his famous Deep Sky Objects catalogue as a list of objects that weren’t comets – his primary goal beimg finding those “hairy stars.”)

    @56. Poul-Henning Kamp : Huge stein of beer cheers! ;-)

  60. Messier Tidy Upper

    @58. James :

    (44) Messier Tidy Upper already raised the subject of the fates M101 and the Magellanic clouds and other large satellite galaxies. I’m wondering what happens to all the the other galactic halo objects, like globular clusters and LSB galaxies, that will be caught in the gravitational crossfire long before the spiral arms start to wrestle. Wouldn’t they slurp up a lot of the ejected gas and dust and spark up into galaxies in their own rights?

    Not sure but we’d be talking an awfully huge amount of gas and dust and stars for that to happen! So I could be mistaken but I don’t think so.

    Our Milky Way is currently merging with at least a couple of small galaxies – the Sagittarius and Canis Major dwarfs. I think the Magellanic Clouds will eventually merge with the Milky Way too but not sure when – and ditto the major satellite galaxies of Andromeda, M32 and M110, with their primary galaxy – but could be wrong.

    Could be merging with us, could be merging with “Milkomeda” or could, just perhaps, be ejected into intergalactic space and out of the Local Group generally, not sure. Would love to see an animation or paper on it.

    For that matter, the Local Group is currently dominated by the two big spirals; wouldn’t the massive new elliptical just overwhelm and slurp its way through a buffet of M33 and the other survivors of the big gulp?

    It will take time – millions or billions of years but I suspect in the end the Local Group (of galaxies) could well engulf and combine all its present members into one super-galaxy – the “Milkomeda plus more.” Looks from that animation like M33 would end up orbiting the Milkomeda elliptical and could well eventually spiral into it, but dunno.

    Anyone know and care to illuminate us all here?

  61. Ivan Pantaleão

    @37-Other Paul: Well… ok, now that you clarified things a little bit more (I don’t even feel myself as one of those “bunch of long dead monkeys” anymore! :p), I think that, just for the sake of celebrating it, I’ll have some beer… oh, wait!! (those pesky long dead Monks and their dreadful inventions… LOL)

    cheers!

    ————————————————————————————

    @44-Messier Tidy Upper: Portuguese, Spanish, Italian, French, and many, many more languages are all Romance languages (or Romanic languages, Latin languages or Neo-Latin languages); it happens that, in Portuguese, Earth = Terra — ipsis literis! :)

    Here you are some of the “main features” of our solar system (“sistema solar”) in Portuguese:

    Sun = Sol
    Mercury = Mercúrio
    Venus = Vênus
    Earth = Terra, Moon = Lua
    Mars = Marte
    Jupiter = Júpiter
    Saturn = Saturno
    Uranus = Urano
    Neptune = Netuno
    Pluto = Plutão, Charon = Caronte

    and last, but not least, Milky Way = Via Láctea

    cheers!

  62. Pirran

    “TechyDad Says:
    May 31st, 2012 at 1:12 pm
    Ok, we have a few billion years to hammer out the important matters: What would we call this new galaxy? I’m lobbying for Mildromeda Way.”

    Don’t be absurd….It’s obviously Andy Milk….

  63. Peter R

    I propose we call the new galaxy Milkdromeda, the warrior dairy princess.

  64. Ivan Pantaleão

    Being even more off-topic:

    my first language is Brazilian Portuguese (pt-BR) and not Portuguese (pt-PT); there are subtle, but meaningful differences between them, that take them further and further apart, as they evolve by themselves… sometimes I find myself more comfortable reading Spanish, French and even English (mind you!) than the old, plain Portuguese, from Portugal. And I know they “kind of” feel the same about our “new” language! :)

    cheers!

  65. SkyGazer

    *puts 4.000.002.012 in his agenda*
    Thanks for the update!

  66. Len

    Collision will be on a Tuesday…Best advice…stay indoors!!

  67. SkyGazer

    @64. Len Says
    From when to when?

  68. BCL1

    I guess that I have a question about the exact nature of the collision. Why don’t the galaxies pass through eachother and just keep on moving (but deformed by the gravitational interaction)? Obviously, kinetic energy is lost in the collision (as ultimately it is an inelastic collision), but how? Is it essentially “friction” caused by the interaction of interstellar gasses? If so, what is the effect of all that heat? I suppose that it is realeased slowly over millions of years, so it isn’t that important.
    Thanks.

  69. In re: what others mentioned again about Triangulum, my understanding is that we don’t quite know yet. It’s possible Triangulum will merge with Andromeda and the Milky Way at some point after the two merge, it’s possible it will merge with one or both before they merge, it’s possible it won’t merge at all. We just don’t know quite yet.

  70. In re: what others mentioned again about Triangulum, my understanding is that we don’t quite know yet. It’s possible Triangulum will merge with Andromeda and the Milky Way at some point after the two merge, it’s possible it will merge with one or both before they merge, it’s possible it won’t merge at all. We just don’t know quite yet.

  71. Lascas

    62. Ivan Pantaleão:

    pt-PT and pt-BR in literature are very similar, only slang is very different. Reading a book in PT or in BR is almost the same, except for those tricky slang twists that totally ruin it :P
    “A rapaz estava a gozar com a rapariga”
    Nothing wrong with that sentence in pt-PT, but in pt-BR… you know what i mean :P

  72. kat wagner

    @Other Paul – once I heard a stranger (from another country I guess) pronounce “Milky Way” and put the emphasis on the third syllable and I just thought that was so cool. Or maybe he was on Sesame Street reading “In the Night Kitchen” by Maurice Sendak. Anyway, he made it clear to me that our home galaxy is way more than a candy bar.

  73. drow

    the new galaxy will probably be named “Microsoft Galaxy”, the naming rights having been sold for fifteen septillion uberdollars.

  74. Ivan Pantaleão

    @66-Lascas: (off-topic once more…)

    what to say about: sinônimo x sinónimo, antônimo x antónimo, ótimo x óptimo, etc…

    besides, Brazilian language has been enriched by the adoption of many words from some African dialects (e.g. “bunda”, perhaps the most known and loved! rsrs), among other languages (e.g. my mouse is still a mouse, and not a “rato”, my computer’s screen is a “tela” instead of an “ecrã”, and so on).

    not to mention “o facto de estar numa bicha, a trajar um fato!” ROFL :P

    never mind… ;)

    cheers from Brazil!

  75. Zandro Andalesio

    Author please// :)

  76. Jess Tauber

    As usual the Republican leadership is blasting President Obama’s failure to manage this crisis. In fact, Mitt Romney declared on Friday that during his presidency, while other countries would likely continue fruitless discussions on ways to open negotiations with the Andromedans, the United States would take unilateral military action to prevent them from entering Milky Way space. “I remember the old Star Trek episode about the Kelvins”, he said before a $100,000,000 a plate audience of donors, “and I know what they’re about”. He also reminded the crowd which of the two Enterprise crew members ended up as powder on the ground. “Obama better worry- this time it ain’t gonna be the girl….”- which a Romney campaign spokesperson later denied was a cryptic racist taunt. Meanwhile in Washington a relatively small group of Obama supporters mingled under heavy rain near the Mall cheering on the reelection of the President shouting “Four More Billion Years- Four More Billion Years!”

  77. Gary Ansorge

    Ah, only four billion years to go. I’ll be scalping tickets for the front row seating…

    I wonder how sentients of that era will interpret this phenomena. With universal expansion carrying away distant galaxies, they may have few examples of galactic collisions and might get all excited by what they see coming.

    Can you say “Ack! The sky IS falling…”

    Gary 7

  78. Messier Tidy Upper

    @62. Ivan Pantaleão : Thanks for that. Plus the other Portugese language info. too.

    Cheers from Australia. (“Oz”) :-)

  79. Forgive my physics naivete, but if stars almost never collide, why would the galaxies merge at all instead of simply passing through one another?

    If two stars approach each other and don’t collide, they’ll deflect one another, but their sum total kinetic energy afterward is going to be the same, right? My understanding is that for one body to be captured by another, a third body needs to be ejected to carry away the extra momentum. Does this mean that a significant number of stars must be ejected from both galaxies in order for the merger to happen?

    Or is the mass of the dust and gas that DOES collide large enough to slow the galaxies down? Given the improbability of a tiny speck colliding with another tiny speck in interstellar space, it boggles the mind to think that that much mass (enough to gravitationally drag a galaxy to a stop) would actually collide in such a merger?
    Am I just hopelessly ignorant of physics, here? This is certainly possible :)

  80. @78 Jess Tauber: As usual the Republican leadership is blasting President Obama’s failure to manage this crisis. In fact, Mitt Romney declared on Friday that during his presidency, while other countries would likely continue fruitless discussions on ways to open negotiations with the Andromedans, the United States would take unilateral military action to prevent them from entering Milky Way space. “I remember the old Star Trek episode about the Kelvins”, he said before a $100,000,000 a plate audience of donors, “and I know what they’re about”. He also reminded the crowd which of the two Enterprise crew members ended up as powder on the ground. “Obama better worry- this time it ain’t gonna be the girl….”- which a Romney campaign spokesperson later denied was a cryptic racist taunt. Meanwhile in Washington a relatively small group of Obama supporters mingled under heavy rain near the Mall cheering on the reelection of the President shouting “Four More Billion Years- Four More Billion Years!”

    “The citizens of the Milky Way are sick and tired of Big Government!” said speaker John Boehner (R), in a statement last night in response to President Obama’s urging of Congress to develop a strategy for dealing with the impending merger with the Andromeda galaxy. “Republicans stand behind the principles of personal freedom – we believe that each citizen should be free to make the decision for him or herself how best to deal with this galactic collision.”

    (with apologies to The Onion)

  81. Jess Tauber

    By now some of you may feel that this whole thing is spiraling out of control…

  82. Messier Tidy Upper

    @82. Joseph G :

    Forgive my physics naivete, but if stars almost never collide, why would the galaxies merge at all instead of simply passing through one another? If two stars approach each other and don’t collide, they’ll deflect one another, but their sum total kinetic energy afterward is going to be the same, right? My understanding is that for one body to be captured by another, a third body needs to be ejected to carry away the extra momentum. Does this mean that a significant number of stars must be ejected from both galaxies in order for the merger to happen? Or is the mass of the dust and gas that DOES collide large enough to slow the galaxies down? Given the improbability of a tiny speck colliding with another tiny speck in interstellar space, it boggles the mind to think that that much mass (enough to gravitationally drag a galaxy to a stop) would actually collide in such a merger?

    As I understand it, its the gas and dust that interact and hold the galaxies together causing them to merge – and also perhaps the Dark Matter.

    Mind you, there’s a lot of mass and therefore gravitational attraction among the stars in aggregate – individual stars won’t collide but the combined mass of the hundreds of billions of stars will keep themselves and these “island universes” from flying apart and will help draw them back together and fuse the Andromeda and Milky Way into one.

    From what I gather the gas and dust clouds will start forming stars at a furious rate – perhaps briefly turning the colliding Galaxies* or Milkomeda into a “Starburst Galaxy” before the gas and dust is all used up or dispersed leaving little to form future generations of stars after the collision.

    Also whilst most of the stars will remain gravitationally bound to the new Milkomeda elliptical a number will also be ejected from both Galaxies* and thrown into intergalactic space. It is possible our Sun could be among them although unlikely.

    Of course, the BA has a chapter on this in his ‘Death from the Skies’ book which is well worth reading if you haven’t already too. :-)

    ——————-

    * Our Galaxy is conventionally capitalised separating itfrom other galaxies which are not – but what’s the capital idea here when our Galaxy is one of the Colliding Galaxies in question? Caps I’m presuming, right?

  83. Mephane

    I am highly annoyed by some of the media coverage of this topic. What most of the mainstream media protrait looks like as if this were a) some new and surprising insight and b) something horrible, as if the two galaxies were somehow destroyed in the process, while instead that this would happen has been known for some time and is not tragic at all, as galaxies are not solid bodies that impact upon each other and then spectacularly explode or whatever, but are more like fluids that flow and mix and merge slowly until they form a new structure.

    This is also why I prefer the term “merge” over “collide” when referring to the event, to which I am actually looking forward to, heh.

    On the other hand, I also hope that the universe ends in a “big crunch” instead of expanding and diluting forever… *shrug*

  84. craq

    Dark matter was mentioned in one of the comments here. I’m guessing the Hubble observations don’t give us too much detailed information on that, so what effect could the dark matter have on the collision?

  85. Ashley

    why doesn’t the triangulum galaxy get sucked in?

  86. Messier Tidy Upper

    @ ^ Ashley : Because of its velocity and distance and trajectory I’d guess.

    IOW, its too far away, travelling too fast and taking a different path through intergalactic space.

    However, over the (very) long run this may not save M33 forever as I ‘d guess it will ultimately end up orbiting and perhaps merging with the new Milkomeda elliptical assuming it doesn’t get involved in the M31 – MilkyWay merger to begin with.

    Would be fascinating to see if astronomers can predict the ultimate fate of all the galaxies in the Local Group and calculate and determine their paths and fusings for X billion/ trillion years into the future. Maybe they’ll almost all merge into one then gradually disperse with the end of the Stelliferous era when even the oldest red dwarfs fade to black (many being gravitationally ejected by stellar interactions over aeons) and ultimately head towards the Big Rip if that’s how our cosmos ends?

    Of course, we’ll have to wait a ree-eeeally long time to see how accurate any such predictions turn out to be! ;-)

  87. don fowler

    I thought dopler redshift proved everything was expanding away from us. How can there be a redshift but at the same time the Andromeda galaxy is moving toward us?

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