A Journey into a Galaxy Collision

[@anonymousSWE]

Would you believe me if I said that all this knowledge that science has given us/me has made me a much more relaxed human being. I'm not only talking about astronomy, but all the natural sciences. Add to that the insights of Spinoza and other great thinkers, and voila, a new me. I'm actually happy. And a small part of that happiness is due to you people at the Deep Astronomy channel. You've given me knowledge, and asked for nothing back. For that I will always love you. Thank you so so much!

[@curfewrukidn]

I've marked the date in my calendar

[@ryand2829]

Lol

[@Sakanakao]

You've shown some of these images/animations before but it's great to be getting a more detailed explanation of what they mean.

[@esamiga]

Thank you Tony! Lovely having you back!! :-)

[@Ozzywozzy]

Deep Astronomy always has the best astronomy videos and seriously Tony the narrator has a perfect voice fitting the aura of each video. Keep us looking up!

[@CarlosFaria]

As always a perfect video from Deep Astronomy!

[@sprig3432]

Kerbals are proud, well done champ

[@michaelmacomber]

Was wondering when we'd hear from you again Tony. Worth the wait! Awe inspiring video man. Do more work.

[@BurntBrian]

I love all of the videos from Deep Astronomy. Lots of great information regarding Galaxy collisions with amazing visuals. Thanks for educating us =)

[@thenewvoice8]

awesome as always!! Cheers Tony.

[@chezpapa3]

I don't want them to merge; the milky way looks so much better in the sky rather than the big eliptical galaxy, oh well, theres no stopping it and it's not like i'm going to be around to see it anyway.

[@jeandannemann]

this is amazing... the way I see the space is the way as you were born into an isolated island an only had the ocean to watch on the horizon.. I wonder myself everyday what is on the other side

[@HolloVVpoint]

Man the scale of it all, in mass and time is just mind boggling.

[@michelpijnen1276]

Yet another awesome video! Thank you so muchhhh!

[@cr4zyuk2008]

Amazing as always, wish more people would watch your videos

[@Bobajobimus]

Is that the music from Kerbal Space Program at the end? Nice touch. A pleasure to watch, as always.

[@edpozek]

What it would look like has been a question in my mind since I first heard of the collision when I was young. Thank you for that, it was really was moving.

[@DannyECDUB]

What happens to supermassive black hole in our galaxy and that one of the Andromeda when it collides? How do the 2 singularities interact?

[@beta5770]

only the supermassive blackholes merge and some stars die :/

[@xBaRLoGx]

lolz, I asked exactly the same question without even looking at comments :D

[@CastorQuinn]

Singularities don't interact, or not in any way that physics can describe. The two black holes have incredible gravity due to their incredible mass, and those masses will merge, creating an area of even higher gravity than before. This is similar to two stars colliding, or to a moon crashing into a planet, or to two bodies accreting during planet formation - some mass would be thrown off as energy, and the rest would settle under gravity into a single object. The event horizon of the new object would be larger than before, as it is a function of the object's mass (more or less). What happens to the content inside the event horizons, though, is anybody's guess; the definition of a singularity is the point at which our physical description of the universe breaks down.

[@beta5770]

Castor Quinn event horizon as a function of the object's mass?

[@CastorQuinn]

Kashiv Ranik Yeah, as I understand it the event horizon is the region within which the gravity is high enough that it bends light to such a degree that light cannot escape the area. So the event horizon of a black hole is a function of its mass.

[@ElimAgate]

Your videos always astound me. Please keep up the great work! This is a work of art!

[@DTiberius]

This is a masterpiece, Tony. Thank you.

[@ogunbaboy]

When I was a little kid, I used to call these celestial orgies. Only when multiple galaxies were bound to collide. Then I used to sit in my blankets depressed because I wouldn't be around to see the show.

[@BlackEpyon]

Oh, but you can! just look at the Hubble pictures :D

[@ogunbaboy]

BlackEpyon But I have to see our own galaxy getting it on with our neighboring galaxy. Its going to be spectacular.

[@BlackEpyon]

OMGitsMoose Maybe they wanna take it slow ;)

[@mrjackbilbo]

Thanks for the upload

[@anulovlos]

The Kerbal Space Program music did not go unnoticed. Great video!

[@SOBIESKI_freedom]

Amazing.

[@slickstersf]

That was really nice to watch.

[@NorthofNorthIsland]

Very cool to watch on a 60" close up. Mind blown atm...

[@better.better]

Excellent piece!

[@illusionz9053]

The vastness of space never fails to awe me no matter how many times I think about it. The face that 2 galaxies can merge with very very very minimal collisions of stars just attest to this. People just don't understand just how vast the universe truly is, including myself of course. I like to belief I have a better understanding and conception of it than most people who don't spend hours upon hours trying to imagine it like I do but even then I think I may just be fooling myself. I mean, a millions A LOT. A 100 million even more ridiculous. Then you have a billion which is absurd. A 100 billion which is even mind shattering. Then to think of a TRILLION. It's so unfathomable the even comprehending how unfathomable it is unfathomable. Now, to think there is over 100billion galaxies all containing billions or trillions of stars which are staggeringly larger than earth itself. Now think of just how big even earth it. How but continents, countries, even states are. Just wow.

[@Jenab7]

I estimated that there'll be about one stellar collision per 60 billion stars (in both galaxies); however the stability of planetary systems is a different matter. A star with an extensive family of planets has about 1 chance in 300 that the orbits of its outer planets will be disrupted by a passing star during a galaxy collision.

[@112jungle]

Awesome video

[@GoreTorn16]

Phenomenal. Thank you Tony!

[@khanderaopareekshannarende9417]

Wonderful narration....

[@mourntheloss666]

my god this video was incredible!

[@NataliaSantoro]

amazing video! Thank you!

[@Hawtsaus]

Great presentation :)

[@polynikes158]

so amazing! show us more!!!!!!

[@BattleBunny1979]

stunning stuff!

[@kdaniel1995]

Kerbal Space Programm music, its so magical.

[@okrajoe]

Amazing animation.

[@cryionic]

Thank you, Tony

[@MisterCactus777]

I wish I could be around to see this. What an event!

[@dewinthemorning]

This is an excellent clip from the tv programme "Cosmos". That's good science, condensed and narrated by Neil de Grasse Tyson for the general public. More of them are necessary!

[@sillyrunner1]

At 6:24 starts some music that's in Kerbal Space Program.

[@jura3899]

Thanks tony :) i wish I could be around to see that. I wonder why the newly merged galaxy becomes an elliptical galaxy? Why not just a more massive spiral galaxy?

[@clutch1141]

During a merge the neat and ordered orbital patterns of stars around the galaxies centers along distinct orbital planes is torn apart by extreme gravitational disturbances by the presence of a second galactic center, the influx of billions of new stars that weren't there before and all of the new vast clouds of gasses and dust. After the merge is complete the new galaxys stars will orbit the center in random patterns that follow no ecliptic plane as before, and all of the gas and dust clouds that compose most of the matter in the spiral arms will rush toward the center very rapidly resulting in a massive increase of new star formation several orders of magnitude higher than before the merge.

[@kingdomdom1]

Two masses moving toward one another do not just merge.

[@jura3899]

Thanks john lacy :) kingdomdom, I know that two massive objects don't just merge. I was trying to understand why the newly formed galaxy from the merger was elliptical and not spiral.

[@Mathman1ac]

I'm my work on quantum computing works, I may be able to download the consciousness of a human into computers within your lifetime. As long as everything goes well, you may live long enough to see this happen afterall.

[@michaelmacomber]

I thought it was a good question K.

[@Randomvideos3200]

You're alive!

[@wevebeenattacked1757]

what happens with the black holes of both galaxies when they collide? Do they simply merge together or some weird shit happens?

[@jonbold]

The black holes in the centers of galaxies contain more matter than the rest of the galaxy because, as matter starts to move very fast in the accretion disc, all the leptons, the protons and electrons, lose their repulsive functionability and all the matter collapses to something very dense like the neutron star matter. It continues to spin into the black hole with ever more speed. The accretion disk can contain all this cold matter with no problem. If two heavily loaded black holes collided, a large percentage of that matter would slow down in the collision and expand into normal matter. I think that mess would qualify as some really weird shit.

[@tscoffey1]

+Jon Wiebold The supermassive black hole at the center of our galaxy is estimated to be about 6 million suns in mass. This is an insignificant percentage of the mass of the entire Milky Way (400 billion stars).

[@jonbold]

+tscoffey1 I stand corrected. Thanks.

[@rockochimp545]

hehehe, 7 billion year time laps of galaxies changing with identical mountain view.... one of my fav channels though!

[@lotanerve]

I'll mark my calender.

[@PTNLemay]

6:25 KSP music!

[@NoPetition]

Wow! You are using music from KSP! Adds even more to the immersion :D thanks

[@Werrf1]

I got near to the end of the video, multitasking a bit, and thought I'd accidentally started up Kerbal Space Program when the orbit music started up!

[@alvindickens3622]

Question: I've seen a video that suggests that the halo of hydrogen that surrounds Andromeda and the one surrounding the Milky Way may have already started colliding! Is there any validity to that?

[@alvindickens3622]

If so, what kind of time frame would there be for the possibility of star formation between the two galaxies?

[@smazzii-7670]

someone knows the music at the beginning?

[@zarkoff45]

What a night sky it will be, if there is anyone around to see it, to look up into the sky and see this huge galaxy coming at us.

[@esdev92]

It won't be visible to the naked eye. If it were, you could have already seen Andromeda by now (it would have a diameter of the Moon). Same reason why can't you see the center of our galaxy now. The only difference will be twice as stars in the night sky. It's because light disperses over interstellar space as it travels. That's why we use telescopes to "collect" dispersed light and focus it to make an image.

[@Niosus]

Palatz You can see Andromeda in the night sky, it just has to be dark enough. Light pollution in many urban areas drowns out Andromeda.

[@woofhound]

I look at this type of event and wonder what it would be like to look up and see it for real.

[@colloquialmind2167]

According to this video, the collision between the Milky Way and Andromeda would give us a light show? I was thinking that the collision of our galaxies might not be terribly kind to us.

[@Randomvideos3200]

Kerbel Space Program music there at the end? :D

[@intrepidxprodigy91]

No. Royalty-free music that is used in countless videos and games, including KSP.

[@SMOCZYLAS6]

i really like this episode. also great cgi and pictures

[@igivup4815]

Questions.. What is the fate of a star that is flung out of its galactic home? If our sun was flung out of the milky way during a merge with Andromeda what would happen to us and the planets orbiting the sun?

[@Graeme_Lastname]

And in the end there were more stars but less density?

[@steveshomes]

what an amazing video thank you

[@rkreike]

Q: There are colliding galaxies, galaxies that move away from each other, and galaxies that are in a standstill to each other? Or not?

[@benworthing]

Was the narrator MAX from flight of the navigator?

[@xBaRLoGx]

What will happen if two galaxies that have Super Massive Black Holes as their center, collide. To be precise, what will happen during collision and how will the galaxies be affected after that?

[@trippplefive]

is it possible for the two super massive black holes to get so big in the collision that they start sucking up the stars and planets around them?

[@Kettlemin0]

yes

[@tjpratt87]

Good choice of music when the milky way and the adromida Galaxy merge #kerbalspaceprogram

[@ketfoen]

I'm planning on living forever to witness this. :P

[@williamwalker2096]

I have my popcorn ready.

[@BRTSNful]

6:23 KSP Tune :D

[@Leon612]

Part of me always thinks I'll still be around when this and other wild things are supposed to happen in millions and billions of years from now. Oh well...

[@legna20v]

I have a question that is been killing me in forever .. how is it that lot of stars are no adsorb by the super massive black hole in the center of the galaxies on this galaxies collisions making then a double quasar ?

[@DavenH]

unless they get close enough to get sucked in, which is a small window in cosmic terms, they stay in orbit

[@CastorQuinn]

A black hole doesn't suck, it is simply an object with high gravity. Think of our sun - it is an object with high gravity, and the planets of our solar system orbit around it. A black hole is the same. In fact if our sun were today replaced with a black hole of the exact same mass as our sun, our planets would remain in orbit, just as they are now (except a lot colder because there's no sun anymore). A black hole does not suck, it is just a very heavy object with a lot of gravity.

[@BlackEpyon]

Castor Quinn It should be noted though, so people don't get confused, a star of our size won't become a black hole :/ Just a white dwarf. While many larger stars go out in a blaze of glory, ours will die with a whimper.

[@MustObeyTheRules]

Wow I wish I was around in 4 billion years I couldn't imagine

[@kieron698]

6:30.. We made it to space everyone!!!!woooo

[@bignitro50]

KSP music ha!, but honestly loved the video.

[@rkreike]

Q: Hydrogen doesn't exist since the Bigbang, but is a product of evolution of the universe? Before there were visible stars, there already were "dark planets and stars?" In the universe exist many "dark planets and stars" possibly older than visible stars?

[@engdallal]

Fantastic

[@TOTMGreenish-Top-Of-The-Morrin]

@ 3 billion years ... where in the milky way will our star be --- are we being sucked toward the center ... or flung away out here on the edge

[@Mishimized]

And Now I am Bummed that its impossible to see such a view with my own eyes. *Sniff Sniff*

[@EdgarTorres-ky3fd]

=o I wish cosmology had big career opportunities :(

[@tritonmole]

I wish i was a rock, orbiting the sun, living unimaginably long life and saw what wonders are to come!

[@Jenab7]

The Andromeda galaxy and the Milky Way galaxy are presently separated by r₁ = 2.54e+6 light years = 2.40303e+22 meters The mass of the Andromeda galaxy is 1.5e+12 solar masses. The mass of the Milky Way galaxy is 8.0e+11 solar masses. One solar mass is 1.98855e+30 kilograms. The combined mass of the two galaxies is M = 2.3e+12 solar masses = 4.57367e+42 kilograms The gravitational constant, G = 6.67408e-11 m³ kg⁻¹ sec⁻² The gravitational parameter of the two galaxies' mass is GM = 3.05250e+32 m³ sec⁻² The galaxies are presently moving toward each other, having a radial a speed of v₁ = −110000 m/s How much time will elapse between the present and the moment the two galaxies are separated by a distance of 200,000 light years? How fast will the two galaxies be moving with respect to each other when their separation has been reduced to 200,000 light years? The distance that would have separated the Andromeda Galaxy from the Milky Way Galaxy, if we were to trace it backwards in time to the point of mutual rest, is found from d = r₀ = [1/r₁ − v₁²/(2GM)]⁻¹ d = 4.58834e+22 meters If two bodies having a total mass M are initially at rest and separated by a distance d, the time to fall until the separation is r, such that r is less than d, is found by integrating a differential form of the Vis Viva equation: v = √[GM(2/r−1/a)] Since the apoapsis of a plunge orbit is twice its semimajor axis, a = d/2 v = √[2GM(1/r−1/d)] Since all the motion in a plunge orbit is radial (i.e., there is no transverse component), ∂r/∂t = √[2GM(1/r−1/d)] We derive an ordinary, non-linear differential equation with variables separable: ∂t = ∂r / √[2GM(1/r−1/d)] t−t₀ = √[d/(2GM)] ∫ ∂r/√(d/r−1) A substitution, u = √(d/r−1) ∂u/∂r = −½ d r⁻²/√(d/r−1) So that, r = d/(u²+1) ∂r = (−2d) u [∂u/(u²+1)²] Then, t−t₀ = −2d √[d/(2GM)] ∫ ∂u/(u²+1)² Integral form solution _(CRC Standard Mathematical Tables,_ 32nd edition, page 296, No.48): ∫ ∂x/(x²±c²)ⁿ = {1/[2c²(n−1)]} { x/(x²±c²)ⁿ⁻¹ + (2n−3) ∫ ∂x/(x²±c²)ⁿ⁻¹ } In which x=u, c²=1, n=2, and the "plus" case is taken. ∫ ∂u/(u²+1)² = {1/[(2)(1)(2−1)]} { u/(u²+1)²⁻¹ + (4−3) ∫ ∂u/(u²+1)²⁻¹ } ∫ ∂u/(u²+1)² = ½ u/(u²+1) + ½ ∫ ∂u/(u²+1) t−t₀ = −2d √[d/(2GM)] { ½ u/(u²+1) + ½ ∫ ∂u/(u²+1) } t−t₀ = −d √[d/(2GM)] { u/(u²+1) + ∫ ∂u/(u²+1) } ∫ ∂u/(u²+1) = arctan u With the arctan function returning radian values, of course. t−t₀ = −d √[d/(2GM)] { u/(u²+1) + arctan u } t−t₀ = −d √[d/(2GM)] { √(d/r−1)/[(d/r−1)+1] + arctan √(d/r−1) } t−t₀ = −√[d/(2GM)] { √(rd−r²) + d arctan √(d/r−1) } The minus sign indicates that the distance decreases with time. But we already know that and we like our times to be positive, so we just remove the minus sign, and *t−t₀ = √[d/(2GM)] { √(rd−r²) + d arctan √(d/r−1) }* As an aside, if r«d then t−t₀ ≈ π √[d³/(8GM)] The time to fall from where the galaxies were when they were at mutual rest (t=t₀) to where they are at present (t=t₁) is t₁−t₀ = √[d/(2GM)] { √(r₁d−r₁²) + d arctan[√(d/r₁−1)] } t₁−t₀ = 5.01638e+17 sec The time to fall from where the galaxies were when they were at mutual rest (t=t₀) to the moment (t=t₂) when their separation is r₂, where r₂ = 200000 light years = 1.89215e+21 meters is t₂−t₀ = √[d/(2GM)] { √(r₂d−r₂²) + d arctan[√(d/r₂−1)] } t₂−t₀ = 6.22578e+17 sec The difference is the amount of time needed for the separation between the galaxies to close from r₁ to r₂. t₂−t₁ = (t₂−t₀)−(t₁−t₀) t₂−t₁ = 1.20941e+17 sec t₂−t₁ = 3.83238e+9 years At t₂ the radial velocity will be v₂ = −556187 m/s And from there it will be about another 80 million years until mid-collision. Since the plunge orbit for Andromeda and Milky Way has a quarter-period of 19.8 billion years, the coming galaxy collision is the first that has ever occurred between them. The universe isn't old enough even for one quarter-period to have completed, so the galaxies must have had some approach speed from the start. Indeed, a little more math will tell you that when the Andromeda Galaxy (the younger of the two) formed nine billion years ago, the centers of mass of the two galaxies were 3,896,390 light years apart and already moving toward each other at 57.06 km/s.

[@CONCERTMANchicago]

In those simulated shots, boy I hope Earth still has mountains building in 4 billion years, if our planets core is still operating.

[@rkreike]

Question: Are binary-stars the result of colliding galaxies?

[@Kettlemin0]

No. although it is possible for it to happen during a galaxy collision that 2 stars could come close enough and become gravitationally bound to each other and become a binary pair but Binary stars are usually made when the gas from a nebulae has 2 large gravity points that are close to each other eventually becoming stars that are bound to the other stars gravity - it is easier to imagine this if you say that Star A is orbiting Star B and will be this way for the ENTIRE lifetime of the stars

[@hotcrossbones]

So after 7 billion years there will be no new star formation AT ALL in our new galaxy?

[@hahaololol]

awesome ;)

[@donjuanelgrande]

Amazing

[@mysteriman9]

beautiful visuals well made call me an optimist but here's to another 7 billion years my fellow humans :)

[@Dv9UnKnoWn3]

BakersTuts?

[@naimulhaq9626]

Big bang theory and the effect of dark energy predicts galaxies moving away from each other, not tumble into other galaxies as observation confirms, proving existing theories incorrect. Is it possible to post an explanation?

[@CastorQuinn]

The expanding universe theory only says that *on average* objects are moving away from each other. At a local level objects can still interact. The nearby galaxies in our cluster are bound by gravity and so continue to interact, even as this cluster is itself moving away from all other objects in the galaxy.

[@naimulhaq9626]

Castor Quinn I agree, but "local" effects remain, as our milky way will tumble into Andromeda in 4 billion years.17 billion years after big bang, expansion has no effect on local effects(?!)

[@CastorQuinn]

Naimul Haq Yep, so there are two forces at play. One is gravity, which draws bodies with mass towards each other, and the other is dark energy, which is driving the expansion of the universe. Gravity's effect decreases over distance, so when objects are sufficiently far apart dark energy is stronger than gravity and will cause them to drift away from each other. Right now, the galaxies in our cluster are close enough that gravity is still a factor influencing them. However what I just said is a dramatic oversimplification of what's actually happening; the truth is a lot more complex, and there is much we don't yet know about cosmic expansion, such as what dark energy actually is and if its value is a constant. Deep Astronomy has discussed expansion before, but maybe a video explaining it in more detail would be helpful.

[@naimulhaq9626]

Castor Quinn I believe there is no end to "more detail", and truth will always remain "a lot more complex". If it is possible for matter to disperse in all directions since our big bang, and if there are many more such big bangs all around (multiverse like), then we can imagine matter from our big bang entering a neighboring one creating all the galactic collisions (?!)

[@BlackEpyon]

Naimul Haq It's the lovely thing about science. There is ALWAYS more to learn ;)

[@jroek90]

I wish we would discover immortality because I dont want to miss this... :(

[@IAMBAINE]

hmm....7 billion years shouldnt the mountains have moved? :D

[@ahsanrahib9958]

I just wish i could see that....

[@Mournful3ch0]

It's a shame that, during the galactic merger, Sol will die. However, considering that this is 4 billion years in the future (and nearly all technological progress has been made in the last 400 years) I have no doubt that Humanity will live on. If we haven't died already to some natural or self imposed catastrophe, that is.

[@stufromoz8164]

Not sure it will be the end of our star at the next collision (Andromeda), it will depend how the galaxies meet, angle of contact, position of contact etc. If Andromeda makes contact on the other side of our galaxy Sol might not be affected as much. And of course it depends on whether sol is still in existence when this occurs.

[@ZBer27]

Stu FromOz I think he means that the sun remaining lifespan as a main sequence star is shorter than 7 billion years (I think it's about 4.5 billion years), by then earth will most likely be gone due to the sun expansion as red giant.

[@stufromoz8164]

Isn't Andromeda due to collide in 3-3.5 billion years?

[@stufromoz8164]

Stu FromOz Some models estimate 4 billion but i think that is a most exaggerated conclusion?

[@ZBer27]

Stu FromOz The Milky Way and Andromeda will START to collide in about 4 billion years, the collision itself will last for about 1.5 billion years and will take another few hundred million years to settle afterwards. By the time the collision settle, the sun will be a remnant star and earth alongside Venus and Mercury will no longer be here.

[@takshitmathur9208]

you really made my day, oh sorry i meant night

[@NoMoreBaths]

Are you 10?

[@ryand2829]

+I Body Scrubs If your asking him that, you might aswell ask yourselfz

[@NoMoreBaths]

+Dexter Peterson You just gave me cancer with that comment, Thnx...

[@stevesawyersdca]

Andromeda has a trillion stars? That's a pretty big number. If I recall... If you spent a million dollars a day since January 1, 0AD, you wouldn't have spent a trillion dollars until 700 years from now. A trillion pounds would be a pile of nearly 10,000 Titanics. If your heart beats once a second for a trillion beats, you'll live to be more than 37,000 years old. And (finally) if you walked for a distance of a trillion feet, you could walk from here to the Sun. And back again. Plus a couple of round trips to the moon. Just saying... it's a REALLY big number (five or ten times the size of the Milky Way, depending on who you ask).

[@garfieldmircea2006]

No, stupid. It's just 2.5x times bigger than the Milky Way (400 billion).

[@flashstep18]

Shut up Steve

[@stevesawyersdca]

Putan Mircea Apparently, it would surprise you to know that no one actually knows for sure how many stars are in the Milky Way (or in Andromeda, for that matter) - any number you hear is only an educated guess that varies wildly. Unless you've personally counted them, contriteness is warranted when criticizing the estimates used by others.

[@garfieldmircea2006]

I am citing armando torres here: _"Shut up Steve"_

[@stevesawyersdca]

Bullying - it's not just for sad, petulant adolescents with self-esteem problems anymore.

[@KsanterX]

Damn, how to stay alive for the next few billion years?

[@jetison333]

You could always stick your self in stAsis for that long. Of course they don't know how to get you out of stasis yet but they can put you in.

[@therealinferno161]

earth's water supplies will have boiled in 1 billion years.

[@jetison333]

Logan Rich why?

[@innertubez]

Jogging and chia seeds. :-p

[@scribejackhammar]

Somehow transfer your consciousness to a computer. It is possible to copy your thought patterns and your memories to a microchip and processor. It's just very tricky.

[@amrikjohal3926]

Nature is so powerfull

[@EvilGuy669]

Would the stars be the same? I mean wouldn't all of the stars that we see today be burnt out in both galaxies? Is the Milky Way and Andromeda producing enough stars to provide these beautiful views 7,000,000,000 years from now?

[@Kettlemin0]

Yes a lot of the stars would have burnt out and would have gone supernova and the gas in both is sufficient to last us the entire collision (but we would all be dead) but after the collision the Milky Way would be an Elliptical galaxy so our galaxies wont have enough gas to make new stars

[@j9dz2sf]

7 billions years... well earth has no chance to see the end of the story since the sun explodes in 5 billions years.

[@ericpeterson5091]

The Sun isn't big enough to explode - it'd need to have about eight times its mass for any really interesting fireworks. It'll cool and expand into a red giant large enough to swallow the Earth's orbit (and maybe Mars', too), then eventually shrink into a white dwarf. The end result is pretty much the same as far as we're concerned, though.

[@Kettlemin0]

The sun will explode and make a planetary Nebula because it is the right size to do it

[@MrPuzzles]

...I'm gonna go play some Mass Effect now. And stare into the galaxy map...