Why is Andromeda coming toward us?

Why is Andromeda coming toward us?
The Andromeda Galaxy will collide with the Milky Way in the future. Credit: Adam Evans

I don't want to alarm you, but there's a massive galaxy heading our way and will collide with us in a few billion years. But aren't most galaxies speeding away? Why is Andromeda on a collision course with the Milky Way?

I don't want to freak you out, but you should be aware that there's a gigantic galaxy with twice our mass headed right for us. Naw, I'm just kidding. I totally want to freak you out. The Andromeda galaxy is going to slam head first into the Milky Way like it doesn't even have its eyes on the road.

This collision will tear the structure of our galaxy apart. The two galaxies will coalesce into a new, larger , and nothing will ever be the same again, including your insurance premiums. There's absolutely nothing we can do about it. It's like those "don't text and drive commercials" where they stop time and people get out and have a conversation about their babies and make it clear that selfish murderous teenagers are really ruining everything for all of us all the time.

And now that we know disaster is inbound, all we can do is ask WHY? Why this is even happening? Isn't the Universe expanding, with galaxies speeding away from us in all directions? Shouldn't Andromeda be getting further away, and not closer? What the hay, man!

Here's the thing, the vast majority of galaxies are traveling away from us at tremendous speed. This was the big discovery by Edwin Hubble in 1929. The further away a galaxy is, the faster it's moving away from us. The most recent calculation by NASA in 2013 put this amount at 70.4 kilometers per second per megaparsec. At a billion light-years away, the expansion of the Universe is carrying galaxies away from us at 22,000 km/s, or about 7% of the . At 100 million light-years away, that speed is only 2,200 km/s.

Which actually doesn't seem like all that much. Is that like Millenium Falcon fast or starship Enterprise Warp 10 fast? Andromeda is only 2.5 million light-years away. Which means that the expansion of the Universe is carrying it away at only 60 kilometers per second. This is clearly not fast enough for our purposes of not getting our living room stirred into the backyard pool. As the strength of gravity between the Milky Way and Andromeda is strong enough to overcome this expansive force. It's like there's an invisible gravity rope connecting the two galaxies together. Dragging us to our doom. Curse you, gravity doom rope!

Andromeda is speeding towards us at 110 kilometers per second. Without the expansion of the Universe, I'm sure it would be faster and even more horrifying! It's the same reason why the Solar System doesn't get torn apart. The expansion rate of the Universe is infinitesimally small at a local level. It's only when you reach hundreds of millions of light-years does the expansion take over from gravity.

You can imagine some sweet spot, where a galaxy is falling towards us exactly as fast as it's being carried away by the expansion of the Universe. It would remain at roughly the same distance and then we can just be friends, and they don't have to get all up in our biz. If Andromeda starts complaining about being friend-zoned, we'll give them what-for and begin to re-evaluate our friendship with them, because seriously, no one has time for that.

Why is Andromeda coming toward us?
The Hubble Space Telescope’s extreme close-up of M31, the Andromeda Galaxy. Picture released in January 2015. Credit: NASA, ESA, J. Dalcanton, B.F. Williams, and L.C. Johnson (University of Washington), the PHAT team, and R. Gendler

The discovery of dark energy in 1998 has made this even more complicated. Not only is the Universe expanding, but the speed of expansion is accelerating. Eventually distant galaxies will be moving faster away from us than the speed of light. Only the local , tied together by gravity will remain visible in the sky, eventually all merging together. Everything else will fall over the cosmic horizon and be lost to us forever.

All things in the Universe are speeding away from us, it's just that gravity is a much stronger force at local levels. This is why the Solar System holds together, and why Andromeda is moving towards us and in about 4 billion years or so, the Andromeda galaxy is going to slam into the Milky Way.

Why is Andromeda coming toward us?
This annotated artist’s conception illustrates our current understanding of the structure of the Milky Way galaxy. Credit: NASA

So, if by chance you only watched the first part of this video, freaked out, sold your possessions and joined some crazy silver jumpsuit doomsday cult, and are now, years later watching the conclusion… you may feel a bit foolish. However, I hope that you at least made some lifelong friendships and got to keep the jumpsuit.

Really, there's nothing to worry about. Stars are spread so far apart that individual stars won't actually collide with each other. Even if humanity is still around in another 4 billion years or so, which is when this will all go down. This definitely isn't something we'll be concerned with.


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Astronomers measure weight of galaxies, expansion of universe

Source: Universe Today
Citation: Why is Andromeda coming toward us? (2015, January 23) retrieved 24 June 2019 from https://phys.org/news/2015-01-andromeda.html
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Jan 23, 2015
"It would remain at roughly the same distance and then we can just be friends, and they don't have to get all up in our biz. If Andromeda starts complaining about being friend-zoned, we'll give them what-for and begin to re-evaluate our friendship with them, because seriously, no one has time for that."
...I'd like to keep my science and millennial banal banter separate please....have journalists really resorted to writing like this? Sad.

Jan 23, 2015
.I'd like to keep my science and millennial banal banter separate please....have journalists really resorted to writing like this? Sad.
I was thinking that all the way through this piece, and if you hadn't said it I was going to. There's something to be said for making dry science articles more readable, but if it has to be dumbed down to tweener level I'd just as soon not see it here.

Jan 23, 2015
Agree. It was a rather glib and trite piece with very little informational substance...

Jan 23, 2015
What else would you expect from Fraser Cain, all of his articles are similar.

Jan 23, 2015
It's like there's an invisible gravity rope connecting the two galaxies together. Dragging us to our doom. Curse you, gravity doom rope!


I would expect this level of writing on a forum or a children's science book, not on a Phsyics news website.

Jan 23, 2015
What else would you expect from Fraser Cain, all of his articles are similar.

an excellent observation. What else would you expect from someone who names himself after a character in a sitcom about a Boston bar?
(Not to mention, a couple of spin-offs...)

Jan 23, 2015
What else would you expect from Fraser Cain, all of his articles are similar.

an excellent observation. What else would you expect from someone who names himself after a character in a sitcom about a Boston bar?
(Not to mention, a couple of spin-offs...)


Actually, that is his real name. He lives in Vancouver, Canada, and these articles are intended for a young audience. I don`t know why Phys.org keeps picking them up. The intention, however misplaced, is to try make the science surrounding astronomy interesting to kids.

I`m thinking yàll should lighten up about it a bit.

Jan 23, 2015
And OMG I just realized that Wydening Gyre picked up a quote from cantthinkforhimself and then ***GASP** AGREED with it! WTF Wg were you thinking?

I hope I have clarified Fraser's intent for you. And let that be a lesson - you can't take ANYTHING canthinkforhimself says at face value! He, and the rest of the EU acolytes, have been banned from the AT forums for years. For doing pretty much what he does here - makes stupid claims, gets called on them and can't support them, then goes to the next article in line and makes the same stupid claims all over again. He has an agenda, and damn whatever the facts may be.

Jan 23, 2015
And OMG I just realized that Wydening Gyre picked up a quote from cantthinkforhimself and then ***GASP** AGREED with it! WTF Wg were you thinking?

I hope I have clarified Fraser's intent for you. And let that be a lesson - you can't take ANYTHING canthinkforhimself says at face value! He, and the rest of the EU acolytes, have been banned from the AT forums for years. For doing pretty much what he does here - makes stupid claims, gets called on them and can't support them, then goes to the next article in line and makes the same stupid claims all over again. He has an agenda, and damn whatever the facts may be.

Even rabbits can say something decent Once in a while...:-)

Jan 23, 2015
And I just got the word - My blood daughter is pregnant... Gonna be a real grandpa, not just through my step kids...

Jan 23, 2015
And I just got the word - My blood daughter is pregnant... Gonna be a real grandpa, not just through my step kids...


Well double grats then - both on the new one coming and the one(s) already here! Honestly no need for delineation WG, they are all your grandchildren.

You haven't commented on my take of the lesson to you. I am not saying that well, but I'm not sure how better to put it. Don't believe anything you hear from cantthinkforhimself without checking first?

Jan 24, 2015
And I just got the word - My blood daughter is pregnant... Gonna be a real grandpa, not just through my step kids...


Well double grats then - both on the new one coming and the one(s) already here! Honestly no need for delineation WG, they are all your grandchildren.

Thanks, Mag. Was there within hours to welcome for all of their arrivals. Still, something a little extra special bout yer own blood connections...:-). Instinct of some sort, maybe?
I'll never consciously treat them differently because of it, tho...
You haven't commented on my take of the lesson to you. I am not saying that well, but I'm not sure how better to put it. Don't believe anything you hear from cantthinkforhimself without checking first?

Frazer C. writes in a recognizable form that does tend to dumb down a topic. CD recognized that and I felt it appropriate to positively comment.
I'm just a guy that thinks there's hope for everyone...:-)
('cept for maybe JVK...)

Jan 24, 2015
('cept for maybe JVK...)
Lol well, and uba the moron and canthinkforhimself. But ok, point taken!

Congrats you ROC!

Jan 24, 2015
('cept for maybe JVK...)
Lol well, and uba the moron and canthinkforhimself. But ok, point taken!

Congrats you ROC!

Actually a SWOC (still working ol' codger)

Jan 24, 2015
It's like there's an invisible gravity rope connecting the two galaxies together.


There is likely an "invisible rope" connecting the two galaxies, however it is an electric Birkeland current not a gravity rope.

Jan 24, 2015
This comment has been removed by a moderator.

Jan 24, 2015
There is likely an "invisible rope" connecting the two galaxies, however it is an electric Birkeland current not a gravity rope.
No evidence for it exists. After all, if the galaxies would be charged up to level, which would outperform the action of gravity, they would explode already well before they could interact mutually as a single bodies. The electric Universe model is nonsensical, as it considers the electric action at large distances, while it completely ignores its consequence at the smaller ones.


Holy crap Zephyr, I am impressed! A five for you today!!

Jan 24, 2015
No evidence for it exists.


Really?

http://io9.com/ou...05762919

http://www.space....ers.html

Of course there is no fictional DM present, just electrodynamic baryonic matter.

After all, if the galaxies would be charged up to level, which would outperform the action of gravity, they would explode already well before they could interact mutually as a single bodies.


Charge separation at a fraction of 1% will outperform gravity. The rest of your comment is meaningless banter.

as it considers the electric action at large distances, while it completely ignores its consequence at the smaller ones.


More meaningless banter which is a complete obfuscation of reality.


yyz
Jan 24, 2015
"Of course there is no fictional DM present, just electrodynamic baryonic matter."

Then provide a link to the peer-reviewed paper that describes the "electrodynamic baryonic matter" filament between Abell 222 and Abell 223.

You can't because it doesn't exist!

And just to rub your nose in it, the dark matter filament between Abell 222 and Abell 223 was discovered by *gravitational* lensing: http://arxiv.org/abs/1207.0809

[And to be extra nasty, a Birkeland current between these galaxy clusters would radiate strongly in the microwave. Of course, no microwave emission is detected between these galaxy clusters.]

Jan 24, 2015
This comment has been removed by a moderator.

Jan 24, 2015
This comment has been removed by a moderator.

Jan 24, 2015
What else would you expect from Fraser Cain, all of his articles are similar.

an excellent observation. What else would you expect from someone who names himself after a character in a sitcom about a Boston bar?
(Not to mention, a couple of spin-offs...)


Actually, that is his real name. He lives in Vancouver, Canada, and these articles are intended for a young audience. I don`t know why Phys.org keeps picking them up. The intention, however misplaced, is to try make the science surrounding astronomy interesting to kids.

I`m thinking yàll should lighten up about it a bit.


A rational post, somewhat rare.

Jan 25, 2015
Then provide a link to the peer-reviewed paper that describes the "electrodynamic baryonic matter" filament between Abell 222 and Abell 223.


Here is a concept that describes these self forming plasma filaments, based upon studies of laboratory plasmas and combined with the understanding of the fractal nature of plasma processes.

http://cosmology....hkin.pdf

http://plasmauniv...S-06.pdf

http://www-pub.ia...p_17.pdf


Jan 25, 2015
Then provide a link to the peer-reviewed paper that describes the "electrodynamic baryonic matter" filament between Abell 222 and Abell 223.


Here is a concept that describes these self forming plasma filaments, based upon studies of laboratory plasmas and combined with the understanding of the fractal nature of plasma processes.

http://cosmology....hkin.pdf


Don't get your hopes up. The 5 was a mistake, especially since your links were not peer reviewed.

Jan 25, 2015
Well that is one theory. Unfortunately It is very flawed. The whole concept from the "Big Bang" theory of universe expansion, to the expansion dynamics listed above mean this. First you would have to throw away 90 percent of the current accepted laws of physics. Then you would have to write an entire new set of laws of physics. And this is all based on the observed "red shift" Of galaxies when viewed by telescope. Here is another theory. The red shift is caused by the galaxy's collective gravity. A weaker version of a black hole. Kind makes sense doesn't it? And we get to keep our current laws of physics intact. If the universe was expanding, there would be no colliding galaxies. instead there are and have been many collisions.

Feb 02, 2015
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Cosmos Quest-4-Nature Divine By Vidyardhi Nanduri
http://www.youtub...ure=plcp
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