I have been getting some interesting mail and comments about the Alien Sun issue. Several people are pointing out that I have been saying the Sun is native to the Milky Way, but I have no proof of that.
They’re right. I don’t. I’ve been a little sloppy in my terminology. The way I have been phrasing things makes it sound like the Sun was definitely formed in the Milky Way Galaxy, and we don’t know that for sure. What I should be saying is that we know it didn’t form in the Sagittarius Dwarf galaxy. That much is positive.
But this isn’t the first galaxy the Milky Way has cannibalized. It’s not even the only one we’re eating right now! And over time, no doubt the Milky Way has eaten several other galaxies. The Milky Way has been around for at least ten billion years, long enough to ingest other galaxies and discard the evidence. If a dwarf galaxy happened to impact our own in the plane of the disk, it might be very hard to tell what stars were originally "ours" and which came from the interloper. And given that the Sun is only 4.6 billion years old, it’s possible that some of the gas from which it formed came from Out There.
So I cannot say for sure that the Sun was born in the Milky Way, or is made from 100% Milky Way parts. I don’t know if we could ever prove it… or not. Given our location, our orbit, and other factors, it seems likely the Sun has been here the whole time. But there is always room for doubt.
So let me be clear: the Sun is not from the Sagittarius dwarf galaxy the Milky Way is currently eating. We know that. And if I had to bet, I would put money on the Sun having lived its whole life here in the Milky Way. But I’ll try to be more judicious in my phrasing in the future.
June 29th, 2007 at 7:58 am
If our sun did come from the Sagittarius Dwarf galaxy, does that drive down land values in neighboring Milky Way star systems?
Regards
Roy Mengot
June 29th, 2007 at 8:03 am
It’s good to see that BA is still making vapid judgements that are not based upon “the study of observable phenomenon”… but rather subjective conjecture based upon assumptions pulled out of ones glut max.
So now that you have determined the origins of our planet, I think someone should nominate you for some kind of “prize”. Since BA has been able to figure out something that NO OTHER science institute, PhD, or think tank could even touch.
Bold proclamations from a person who thinks that anyone who begs to differ w/ “the astronomical community” is a “far right winger”.
BA blog is full of non-science and politically idiotic diatribes plain and simple… and the fact that you got called out on making stupid planetary assumptions proves that you engage in this type of activity at least once every 3 months.
June 29th, 2007 at 8:16 am
I was going to post a lengthy reply to Mike J, but then I recognized who he is. Remember this little romp, BABloggees? I don’t feel too strongly about the need to reply.
June 29th, 2007 at 8:25 am
Mike J said:
“It’s good to see that BA is still making vapid judgements that are not based upon ‘the study of observable phenomenon’… but rather subjective conjecture based upon assumptions pulled out of ones glut max.”
…except everything he said was based on “observable phenomenon” as you so eloquently call it, such as the sun’s orbit around the center of the Milky Way galaxy, it’s iron content compared to stars in the Sagitarius Dwarf…
“So now that you have determined the origins of our planet…”
I must have missed that post.
“…I think someone should nominate you for some kind of ‘prize’. Since BA has been able to figure out something that NO OTHER science institute, PhD, or think tank could even touch.”
Actually, “BA” used research other scientists have done that confirm the idea the sun is part of the Milky Way. So, what are you refering to?
“Bold proclamations from a person who thinks that anyone who begs to differ w/ ‘the astronomical community’ is a ‘far right winger’.”
No, I think what “BA” is really trying to say is anyone who claims the sun is part of a different galaxy is completely wrong. But seeing as how ‘far right wingers’ (and ‘far left wingers’ for that matter) are often irrationally wrong, I can see how you’d jump to that conclusion.
“BA blog is full of non-science…”
Prove it’s bad science and I’ll believe you. So will “BA” for that matter. I think these correction posts clearly show that “BA” is not afraid to fix errors in his posts or change his mind completely if someone proves he’s dead wrong. Which no one did, by the way.
.”..and politically idiotic diatribes plain and simple…”
What was so politcal about this issue?
“…and the fact that you got called out on making stupid planetary assumptions proves that you engage in this type of activity at least once every 3 months.”
Huh? What stupid planetary assumptions? Did the word “planet” even appear in any of these posts?
June 29th, 2007 at 8:30 am
Darn it! “BA” posted before I could finish. I was feeling spirited, so I decided to take him on. I was mostly curious how his mind turned this into a politcal issue. I should have remembered that whole “Eris” tiff.
June 29th, 2007 at 8:37 am
Phil… too bad you can’t figure out a way to ban the fool.
I just want to know…. are we sure the sun is our sun? What if something comes and wants it back some day?
June 29th, 2007 at 8:43 am
Hi, I think this is the first time I comment in this blog, but I’ve read it since long time ago. I love it.
And back on the topic, I was going to say that if the Milky Way cannibalized other dwarf galaxies in the past, they are actually part of it now, so you could safely say that the Sun was born in the Milky Way to mean that it’s not from Sagittarius. If it formed from matter that came into the Milky Way some billion years ago, well, that’s now part of what we call “Milky Way”.
I mean, our Milky Way is formed from parts of many different smaller galaxies and all stars in it will come from, or from matter from, one of those previously cannibalized ones, it has not much sense to call a group of them “originally be the Milky Way”, and the rest not. You can see it not as a main galaxy that cannibalizes other ones, but some galaxies that merge into a bigger one.
I hope I stated my point clearly :-/
Take care
June 29th, 2007 at 8:46 am
Correct me if I’m wrong, but Phil is just as human as the rest of us and prone to the occasional mistake. At least he has the decency to admit when he’s made an error and go about correcting it in a sensible and educated manner. I also hope Phil doesn’t ban ‘the fool’. The whole point of this comment box is so people can (ahem)… comment on his blog, whether for good or bad.
June 29th, 2007 at 8:53 am
“Phil… too bad you can’t figure out a way to ban the fool.”
Sadly I’ve been blocked/baned by “this site” for some days now and I don’t know why. The reasons which are named for this ban (”malicious activity”, viruses,…) have not been found!
But, well, interestingly that there are still people who thinks that this page is full of “non-science”… ok, “BA” sometimes talks about politics, himself,… but, well, it’s his page here and he can do and let be whatever he wants! And I think in most cases it is about science, even when it’s about politics bacause he talks about politics interferring with science.
June 29th, 2007 at 8:55 am
Well, if the post above was not one of my best
… I regret it, but it was somehow a test if I am able to post here again. And it seems: I can! Now I’m happy, my life has a meaning again 
June 29th, 2007 at 9:39 am
I was going to say something only half-way irrelevant about the Milky Way getting the munchies too, but… XD
I wonder where Mike J. got the ideas that this was political, or about planets? So far as I have seen, it’s the galaxies. Granted, certain celestial bodies might harbor planetary systems, but that was not the topic of discussion.
There’s at least one in every crowd.
June 29th, 2007 at 9:45 am
Kevin, whether he is a fool or not, please avoid the ad hominems.
Either way, he is most certainly wrong.
June 29th, 2007 at 9:52 am
Hm… a couple of points;
1) “conservatives” or especially “neocons” are not the only ones with goofy ideas about science. There’s lots of wierd stuff out on the far left too. They are, however, the ones in power/in the majority right now, trying to stuff their particular brand of goofiness down the throats of students.
2) The temptation to “ban the fool” should be resisted. First, he only covers himself with patent idiocy every time he touches the keyboard, second if he were banned he would cry ‘censorship’ and third, banning him would deprive us of the comic relief factor.
3) Unfortunately, science and politics are inextricably intertwined, especially right now. Every time a scientist opines about things political, commenting, for example, on the evidence for global warming, or whether stem cell research should be federally funded, it intertwines the two. The situation may be frustrating, but it is important for science to collectively lobby for evidence-based political decisions, rather than emotion-based ones. It is also important for science to reach out to “the people” including “the politicians” and open a dialog, since the government is the one entity with the deepest pockets for funding.
4) I am ‘a conservative’ in a rather old-fashioned meaning of the word, but I do not take offense when someone ‘goes off’ on conservatives. I ‘go off’ on ‘the current crop of fascists who call themselves conservative’ frequently too.
June 29th, 2007 at 9:54 am
The BA posts a reasoned, apologetic clarification…and Mike J posts a childish rant in response. Take that for what you will about their respective political positions.
June 29th, 2007 at 10:11 am
First time poster / relatively new reader.
I have a question on the more scientific topic. I have read the comments on the first couple posts on the subject of the galaxy collision and no one has mentioned the first thing that came to my mind when seeing the pic and videos.
I am not an astronomer in anyway, just a skeptic who is amazed by the universe and it’s wonders, so this may be obvious to the likes of the BA and other astronomers. Are we going to get pummelled? We are very close the where the dwarf appears to cross the MW (assumign the immage is correct). It was mentioned in an earlier coment that the timescale is so great that it wouldn’t happen in our lifetimes which make sense, but what are the odds that it wil hapen eventually? Call it a morbid curiousity
What a fireworks show that would be!
June 29th, 2007 at 10:23 am
@Demented:
Well, actually, the distance between stars is so big compared to its size, that most of them pass between the colliding galaxy ones and the galaxies go through each other, like phantoms. But the gravitational interactions work affecting the trajectory of each star, causing the structure of the galaxies to stretch and contort, and the result can be the one you see in the images (the rests of the Sagittarius galaxies), or even more spectacular. You can see some simulations of colliding galaxies in the next link:
http://www.galaxydynamics.org/
But, responding to your question, the odds will be very low, I think.
Regards.
June 29th, 2007 at 10:25 am
Argh, please replace the sentence in brackets in my comment with “the remains of Sagittarius galaxy”. Sorry
June 29th, 2007 at 10:27 am
I agree with DarkSapiens… the odds of us getting whacked with another object are very low. Space is mostly empty. The Saggitarius dwarf galaxy is being pulled to shreds because the MW galaxy has about 10,000 times more mass.
June 29th, 2007 at 10:32 am
Demented:
Don’t worry… it looks like there’s a lot of stuff in a very small space, but in actuallity, the density of stars to space is very low. In fact, two galaxies can pass through one another without any “solid” objects like stars and planets hitting one another. When you think about it, stars are thousands of kilometers wide, but are seperated by light years (roughly 10 to the power of 13 kilometers).
Here’s something you may find interesting… the Andromeda galaxy is potentially on a collision course with the Milky Way! If any humans are still around in a few billion years, they may witness the galaxies merge, but odds are pretty good that even with these giant galaxies “colliding” no stars will crash into one another.
June 29th, 2007 at 10:46 am
Thank you all for your replies
I guess it is easy to forget just how big space is. One should always remember the words of the late, great, Douglas Adams…
“Space is big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the drug store, but that’s just peanuts to space.”
June 29th, 2007 at 11:48 am
DarkSapiens Says: “the distance between stars is so big compared to its size, that most of them pass between the colliding galaxy ones and the galaxies go through each other, like phantoms.”
This is exactly the case. For a more down-to-Earth example, some of you might remember the discussion on vacuum a few months ago where I said the definition of “High Vacuum” is when the chance of a gas molecule running into another one as it transverses a chamber drops below 50-50. With a typical chamber size of 1 meter, that happens at a pressure of about 10^-7 Torr. At that pressure, though, there are still about 100 million molecules per cm^3, meaning that single molecule passes by about 10 billion other molecules on its way across the chamber, and the chances of colliding with one is only 50-50.
I’m not sure what the relative density of stars is proportional to the distance between them, but I think space is considerably less dense than what I just described.
- Jack
June 29th, 2007 at 1:03 pm
Demented - This same topic came up in a post from a month or so ago. I came up with some rough numbers on how vastly empty a galaxy really is. I’ll reproduce what I posted then as I can’t figure out how to link to specific comment:
Take, for example, our Milky Way. A middle of the road estimate puts 100 billion stars in it - spread across a disc 100,000 lightyears in diamater and roughly 1000 lightyears thick. So we can do some back-o-the napkin number crunching and get some rough idea of stellar density in our galaxy.
Volume of the galaxy : ~2.6 x10^51 Km3 (aka. REALLY BIG)
Numbers o’ stars in the sky (ok, galaxy) ; ~100 billion.
This gives us a star for around every 2.6X10^40 Km3. Ok, that’s a hard number to grasp so call it roughly a star for every 310 cubic lightyears or so. Still very hard to grasp isn’t it? Considering that an average star is all of 4.7 lightSECONDS in diameter…. well, you get the idea.
So, if we scale stars to golf ball sizes you’d get 2 golf balls in a space several times larger than the diameter of the solar system. It is safe to say that the probability of stellar collisions in a galactic collison is very, very low.
June 29th, 2007 at 1:19 pm
To be pedantic, isn’t the title “Alien Sun” a bit off? It’s our star, so it really can’t be alien, unless we didn’t come from the same stuff the Sun did. Since that’s not the topic at hand, the question is really whether the Milky Way is an alien galaxy.
June 29th, 2007 at 1:44 pm
Ban me? For saying that Phil needs to be called out more on his , how shall we call them , assumptions?!
The fact is that Mr. BA himself has made several jaunts to other blogs in order to “chime in” on the web-discontenet of the day.. whether it be Eris and Dysnomia, or claiming to know the origins of our planetary system/sun … it would appear the BA finds himself correcting himself an awful lot.
As for my “right wing” comment, it was a jab at phil for calling me right wing when I suggested that the naming of Eris was politically motiviated… (and I might add, I was proved correct by Mike Brown the discoverer of Eris in subsequent interviews ).
Phil does guest spots on the FAR moonbat leftwing blog called Huffington Post, therefore making a reference to his political bias is something that he has opened himself up to by engaging in political forums. But I agree this is not about Phils left wing bias, this is about Phils tendency to make false assumptions, then make half corrections while still trying to save face— so everyone just doesnt say “this guy is pulling stuff out from who knows where, lets find another blog that is based on SCIENCE not personal conjecture”.
June 29th, 2007 at 2:17 pm
MikeJ, Phil did not say he was going to ban you. Perhaps you would like to correct your claim?
June 29th, 2007 at 2:58 pm
I don’t get it. How are the people pushing this making any money off it? Is there a book deal I don’t know about?
June 29th, 2007 at 3:14 pm
To Jack and Stark: Can y’all combine your estimates into one analogy? In other words, if the stars were as small as a molecule (you didn’t say which molecule), how big would the chamber be if it were scaled to enclose the entire Milky Way? Or alternatively, how big would the stars be if the galaxy were scaled to fit inside an average 8′x10′ room? (say 8′ ceilings)
Also, didn’t the space shuttle run some experiments where they dragged a shield behind the orbiter, and measured a vacuum of like 10^-13 Torr or something? I need to look that up…
Seems the odds of us hitting or being hit by another star moving thru our section of the milky way would be on the order of millions to one… but I’m not a statistician.
B-)
June 29th, 2007 at 3:57 pm
Well, in response to this:
“It would appear the BA finds himself correcting himself an awful lot.”
Well, it depends on what you mean by “an awful lot”. When I make a mistake, I do admit it, and try to correct it. That’s how you know for a fact I’m not a right-wing ideologue. But I take exception that I need to do it a lot.
And you might want to look at the polls, since most of the people at HuffPo represent 60-70% of mainstream America on most of the big issues these days. Of course, Deepak Chopra and Robert F. Kennedy, Jr. post there too, and their words could be used as fertilizer. But they’re the exception.
But if the best you can do is tell me that I have to make the occasional correction, then you maybe don’t understand how science works.
June 29th, 2007 at 3:58 pm
Oh, I forgot to add– do you have citations for the interviews with Mike Brown which confirmed what you wrote?
June 29th, 2007 at 8:55 pm
It seem that Mike Janitch is a rightwingnut and that Phil Plait is a good scientist, rarely making errors, but with the intellectual honesty to admit them and correct them publicly without embarressment.
June 29th, 2007 at 9:41 pm
Not only did Phil NOT say he would ban Mike J, but there were a few posts from other commenters reminding the rest of the blog that banning (a) likely would not happen and (b) wasn’t the best course of action. So why is anyone still focusing on that non-issue?
June 29th, 2007 at 9:51 pm
And for all the criticism Phil receives about ‘politicising’ his own blog by (GASP) voicing political opinions, this particular galactic ‘canibalism’ series has avoided becoming a political rant. Until now, when it went off-topic. (The topic was galactic canibalism, alien sun, all that science-y stuff, remember? I’m not saying we should nor shouldn’t discuss other stuff, but it’s interesting that the topic hadn’t been derailed into political back-and-forth ranting until Mike J’s post near the top which basically hammered Phil, and everyone started responding to it.)
Oh, well. Interesting galaxy stuff so far. The Sag D debunking was thought provoking, but so have most of the responses and corrections. Looking forward to reading more.
June 29th, 2007 at 10:18 pm
In Soviet Russia, Milky Way eats YOU!
June 29th, 2007 at 11:21 pm
Skepterist Says: “Can y’all combine your estimates into one analogy? In other words, if the stars were as small as a molecule (you didn’t say which molecule), how big would the chamber be if it were scaled to enclose the entire Milky Way? Or alternatively, how big would the stars be if the galaxy were scaled to fit inside an average 8′x10′ room? (say 8′ ceilings)”
Hmm, why don’t we figure it with relative center-to-center distances relative to the size of the objects. That’s a little cleaner than trying to imagine the galaxy crammed into a standard room.
First, I didn’t say which molecule because there’s lots of different gasses you could be pumping, but let’s use air, which is mostly nitrogen. A nitrogen molecule is roughly 200 picometers in diameter (it’s actually ovoid with a long axis of about 250 pm) or 2×10^-10 meters.
There are one million cubic centimeters in a 1 meter chamber, so with 100 million molecules/cc, that’s 10^14 molecules/cubic meter. Inverting that means each molecule takes up 10^-14 cubic meters. The center-to-center distance would be the cube root of that, or 2.2×10^-5 meters. As a ratio to the nitrogen molecules diameter, that’s 1.1×10^5 diameters apart.
Doing the same thing for Stark’s estimate of the galaxy, he says there is an average of one star for every 310 cubic LY, meaning a center-to-center distance of 6.8 LY. This is 2.1×10^8 Light-seconds. With the average star 4.7 L-sec across in his example, that means the average spacing is 4.6×10^7 stellar diameters.
It’s crude, but that shows that the average spacing of stars in the galaxy is more than two orders of magnitude further apart than molecules in a high vac chamber. Space, therefore, is some 425 times more “empty” than the best industrial vacuum commonly used.
- Jack
June 30th, 2007 at 4:17 am
Dear Mike J.,
Jerfaloo snub carbo. Chicky-poo flipp flipp calamaloo. Ig-jiggy freedo, ap dolisty comobooboohead.
Also: sneeceejee.
And that’s all I have to say about that!
June 30th, 2007 at 5:45 am
Paul: I couldn’t agree more.
However, you neglected to mention that snigloop upjuk incombobulis lololactasee.
Furthermore, new did eht enasni nrel ot esu sretupmoc.
Mike J, you’re quite ungrateful. When are you going to thank Dr Plait for upping your hitcount well into the double figures?
June 30th, 2007 at 8:12 am
Unfortunately this story has been treated in many countries as a real science story. Colombian daily “El Espectador” had it on its front page as a “scientists discover” story.
(The website is down at the moment, so I’ll try to link later.)
June 30th, 2007 at 2:49 pm
Stuart,
I don’t think Mike will take the hint, but I do agree whole-heartedly.
-Paul
June 30th, 2007 at 6:25 pm
The Bad Astronomer
Says:
June 29th, 2007 at 3:58 pm
Oh, I forgot to add– do you have citations for the interviews with Mike Brown which confirmed what you wrote?
—————————
Better than an article, it was on VIDEO!
You can catch a re-airing of the show on the “science” channel. The show was “voyage to the planets: Pluto and beyond”. Just on last week again.
Mike Brown comments on the “political” contraversy, and how the names “resonate” with current geo-political happenings.
Its also basically what Mike Brown said in YOUR OWN interview done w/ him months ago… where Mr. Brown said “he could understand” how [the names Eris and Dysnomia] could be seen in a political light.
But you had already smeared me with the broad brush of “right winger” .. even thought I’m a registered independent who voted for Harry Brown in 2000, and Kerry in 2004…
All for what?! Because I said the naming of Eris and Dysnomia (on 9/11 no less) was a double-speak naming event aimed also at current world events.. and to think I was right and you never retracted.
So please forgive me for jumping on you when you issue a “correction” when making one of your famous “false assumptions” … that I might add are NOT based upon science.
Science is the study of observable phenomenon.
Guesstimations using parralax geometry and making the bold claim that YOU (phil the BA) know for certain where our sun comes from (or certain where it did NOT come from) fits perfectly in line with your other vapid “scientific” observations.
Finally, if you really believe that Huffington Post represents 70% of the population of the USA, either you don’t get out much, or your statistics are just as bad as your “assumptions”.
June 30th, 2007 at 6:30 pm
@Jack Hagerty: can I quote your analysis on my LJ? I think it’s really mind-expanding!
June 30th, 2007 at 6:31 pm
ETA: http:/ /mrteufel.livejournal.com/
June 30th, 2007 at 10:36 pm
Damian Says: “Jack Hagerty: can I quote your analysis on my LJ? I think it’s really mind-expanding!”
Help yourself. Everything I post here is for public consumption. Just remember it’s not peer reviewed
- Jack
PS - A credit would be nice when you post it somewhere…
July 1st, 2007 at 4:54 am
What you you tell us about how we ‘know’ the sun didn’t form in Sag. Dwarf galaxy?
Is is true that our solar system is in the intersection between the milky way and Sag Dwarf?
Is it true that our solar system’s angle of momentem is lined up with the smaller, intersecting galaxy? Could/would a passing ‘rain’ of transient stars torque us about to line up with it, rather than our supposed parent, the milky way?
Thanks for your insight…
July 1st, 2007 at 11:42 pm
Thanks, and credited.
July 2nd, 2007 at 10:28 am
@Mike J:
I’ll leave the political parts alone, but I have to point something out. In your last comment, you said:
By your own words, and Mike Browns’, it seems that what you are asserting doesn’t fly. As Phil pointed out in his first post, Mike Brown points to the astronomy community for the source of the names. Mike Brown saying it “resonates” with and you saying it “could” be political does not mean it is. It only says that you are looking for reasons to make it that way.
July 2nd, 2007 at 5:00 pm
MIchael Sutherland said:
> Is is true that our solar system is in the intersection between the milky way and Sag Dwarf?
No. The Solar System is near the Sag Dwarf intersection with the Milky Way, but not in the stream.
> Is it true that our solar system’s angle of momentem is lined up with the smaller, intersecting galaxy?
No. The Solar System is tilted at an angle to the plane of the Milky Way, but it does not align with the plane of the Sag Dwarf.
> Could/would a passing ‘rain’ of transient stars torque us about to line up with it, rather than our supposed parent, the milky way?
No. For stars to have had that kind of effect, to change the orientation of the Solar System, it would have dramatically affected the orbital paths. The Solar System would not be coplanar, but erratic.
Mike J, you seem to be overreaching. To say that he can understand how one might see the names in a political light is a far cry from stating that he intentionally suggested those names as a political statement, which was your original assertion. You have yet to provide evidence to that conjecture.
Regarding Phil’s comments on the origins of the Solar System, his original response was in relation to the proposal that the Solar System originated in the Sag Dwarf galaxy and was being captured by the Milky Way. His response in light of that proposal was to say it was not consistent with the evidence, and to point out how the proposal was erroneous. In the process of examining that claim, he did go on to state that the Solar System originated in the Milky Way, which in retrospect he clarified was a bit extreme given that the Milky Way has been absorbing smaller galaxies over time, and it is conceivable that it could have in the distant past absorbed a different galaxy that was the original source for the Solar System. However, the timescale for that was significantly far enough back that it wouldn’t mean a hill of beans to us. Also, there’s no evidence to support that notion, so it’s idle speculation with no means for verification one way or another. And most importantly, it does not negate his point that the Sag Dwarf origin proposal is still wrong.
In light of that, it does not appear that you have anything meaningful to contribute, and are just here to whine about your beef with Phil.