Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What is our Solar System's orbital plane around the Milky Way?

  1. Jan 21, 2009 #1
    Does anyone know a good link to an animation or nice diagram showing how our solar system orbits the center of our milky way? I always imagined the milky way's plane, where most of the material is accumulated, as a record, granted, with a bigger bulge and 2/3 out from the center of that record, lies our solar system. Next, I imagined our solar system, which spins around the milky way's center, much like the record spinning. Then, I wondered if there was a wobble in the record and would this wobble give our solar system a secondary orbit as it wobbles up and down, passing through the milky way's plane. This lead to me thinking about how strong the gravity of the plane was at its center and where our solar system currently was on the wobble, in relation to the galactic plane. Next I thought about late 2012, when, astronomers confirm our solar system will pass through the center of this plane. Then, I considered how the sun and our moon effect tidal forces inside the Earth's core and its oceans. Then I thought about global climate change. Finally, I wondered if bovine and automobile flatulence was more powerful then the mass of our entire galaxy, even if it was... far... far... away.
  2. jcsd
  3. Jan 21, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper

    The ridiculous thing about 'crossing the galactic plane' is how you even define the plane. With 3 trillion stars, uncountable number of planets, lots of dust clouds and possibly a black hole in the middle, all of which are constantly moving in different directions, how o you say exactly when you cross the middle of it?
  4. Jan 22, 2009 #3

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2015 Award

    This is utter, complete and total rubbish. Please produce a source for this where a reputable astronomer says this. If you can find one, I'll apologize.

    Great ghu! Don't you have anything better to do than to post such tripe?
  5. Jan 22, 2009 #4
    hahaha you enjoyed reading my 'tripe' thoughts, didn't you.

    Anyhow I've no problem admitting that it could all be crap. So do astronomers have any sense of our solar system's orbit in the milky way? Here is a link to a survey project that 'seems' to consider the galactic plane, at least for the purposes of their survey, about 5 degrees in width. Admittedly however, there is no clear cut definition of the galactic plane.

    Still its a very interesting 1 page read with great diagrams and you will enjoy it. Cheers.


    Here is a model of our galaxy created by Cardiff University, UK, confirming my earlier post about 'wobbling'. At least, their model agrees, but I'm not sure its true of accredited by other experts.


    A visualization of the plane, still, with no defined boundari's unfortunately.


    Upon further reading I have found that in fact, its believed that our solar system has been in the galactic plane since 1998 and so 2012 would be just another year in the plane. However, since no one ever defines the boundary of this plane, from what I've read, this is somewhat meaningless.
    Last edited: Jan 22, 2009
  6. Jan 23, 2009 #5


    User Avatar

    Staff: Mentor

    The "galactic plane" is a man-made reference and not a physical thing. I don't know the accuracy of the determination in the canadian survey (your first link), but due to the size (thickness) of the galaxy and speed the solar system moves around it, there would be no noticeable year-to-year change in our position. The galaxy isn't like Saturn's rings, which are all on an extremely narrow plane.

    Also, "the gravity of the plane" (from your first post) is meaningless. The earth is in orbit around the galaxy center of mass and passing through a region of higher density of stars (say...moving wrt the spiral arms....) doesn't change anything. Freefall is freefall.
  7. Jan 23, 2009 #6
    They recently discovered that our galaxy is twice as thick as what was previously thought, which is a pretty big discrepancy.
    So I would assume we're not actually very close to accurately calculating our true position in the galaxy?
  8. Jan 24, 2009 #7
    Thank you Russ,

    What is the prevalent theory on the properties of the Milky Way's BH? Is it possible for a BH to have a poles like a neutron star, that throw ejecta in 2 well defined regions out from both poles? I'm thinking like a GRB or something, but I'm not sure if the mechanics of a BH allow for such a possibility, or if BH's always radiate uniformly, or something else perhaps.


    PS Hi Vanadium-50
  9. Feb 5, 2009 #8
    I seen something like that on DISCOVERY about Notre Damas predicting the end of life as we know it in 2012. Yeah what ever. It's suppose to end every decade and im still here, but the discovery show went something like this, i.e. 26,000,000 years to orbit the galaxy, 13,000,000 years to orbit half way around, supposedly were coming up on the half way around point, coming up on the bar in the center of the galaxy and all chaos is suppose to break loose cause of the pull from our galaxy. Its got something to do with the MAYA and there calender and where our solar system is at in space in our galaxy. I think if you go here you will see some of it, I only seen part of it, so I might be off on some of it. There trying to get it straightened out at least.

    http://www.december212012.com/articles/news/Apocalypse in 2012.htm

    They even sell shelters for 2012. If the world is gonna end, I don't think the shelter will help any. LOL
    This is what happens when something is put on T.V.
  10. Feb 5, 2009 #9


    User Avatar
    Science Advisor
    Homework Helper

    It actually takes nearer 300M years to orbit the galaxy.
    We do not cross the bar or anything like that - we cross an arbitrary meridian plane drawn near the middle of the galaxy. It's not even in the middle because it was based on older surveys (which is why the centre of the Galaxy isn't at 0,0 )

    As I said in the earlier post it's like assigning some mystical significance to the centre of the USA but not saying if you are including Alaska, or which offshore islands.

    Coincidentally the Maya calender wraps around in 2012, the unix time_t reaches 1234567890 in about a week, and the shelf my DVDs are on is going to be full by my birthday - none of these signal the end of the world.
  11. Feb 5, 2009 #10

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2015 Award


    Which is sort of indicative of the accuracy of the claims of doom and destruction.
  12. Feb 5, 2009 #11
    Hey I was just saying I seen something about it on Discovery. The original question was "Next I thought about late 2012, when, astronomers confirm our solar system will pass through the center of this plane" and someone else said something about Discovery channel. I was just saying I seen it on there, I don't agree with, I just seen it. And I said I might be off on some of it, I didn't watch the whole episode. Oh and thanks for correcting my "Nostradamus". LOL
  13. Feb 10, 2009 #12
    Hi mgb,

    What is the angular velocity we orbit the galaxy at? 300M years you say and we're 2/3 out from the milky's center and our diameter is 100,000 LY wide?

    How fast do we move?

  14. Feb 10, 2009 #13


    User Avatar
    Science Advisor
    Homework Helper

    Assuming values given by the famous astronomer Eric Idle.


    The Sun's orbit around the galaxy is about 220 km/s the distance to the centre is about 30,000lyr
    so its orbital period is actually about 240 million years.
    Last edited: Feb 10, 2009
  15. Nov 21, 2009 #14
    Quoting mgb:The ridiculous thing about 'crossing the galactic plane' is how you even define the plane. With 3 trillion stars, uncountable number of planets, lots of dust clouds and possibly a black hole in the middle, all of which are constantly moving in different directions, how do you say exactly when you cross the middle of it?

    -Yes, this was my first response when I heard all this stuff about crossing the galactic plane. If I draw a line in the sand and cross it, will my world end? [It's so theoretical/imaginary/difficult to pin point.]

    But I am as clueless as the dude who was talking about 'Notre Damas.' [Hey, before any of us heard or read about Nostradamus we didn't have a clue either, so let's not be snobs here even if we sometimes have some fun and amusement. A few centuries from now there will probably be millions of physicists and astronomers laughing at how clueless we currently are and pointing out the mistakes we now see as scientific gospel. None of us were born knowledgeable; we learned what we know from others.]

    So my clueless question to someone knowledgeable about this is: why are some stating that the solar system is several dozen light years north of "the galactic plane" and moving away from it while others are stating that it has been moving through the plane from 1998 to 2016 (at center peak in 2007)? Is this bunk or are they talking about two different points of references that are being confused with one another and distorted? Assuming our imaginary plane in the "center" of the galaxy was "accurate," is one true and the other false? Or are they both false?

    Conversely are they both relatively true (assuming our imaginary plane is quantifiable) but simply talking about two different phenomenon. [I am familiar with the precession of the equinoxes and the earth "wobbling like a top," the "26,000 year rotation," and have heard discussions about this motion being confused with the "solar system moving through the galactic plane." Even though everybody may be arguing over something imaginary and worthless, I'd still like to know what each one is referring to (if anything) when they talk about several dozen light years away versus happening from 1998-2016. Does anybody know?
  16. Nov 21, 2009 #15


    User Avatar
    Homework Helper

    Jennifer: I think mgb's post answers your questions well. The galactic plane simply isn't well-defined. Whereas some people may draw an arbitrary line, call it THE plane, and measure the sun's distance with respect to it, others consider a large area of high stellar density "the plane" and say that the Sun is in the plane.

    See this scatterplot: http://staff.argyll.epsb.ca/jreed/math9/strand4/scatterplot1.gif. Imagine that each of those points represents a star. I want you to indicate the galactic plane. Will you draw an infinitely thin line? If so, where? If I draw a line 0.1 mm above yours, who's wrong and who's right? Will you draw a 1-mm-wide line and say everything the line covers is the galactic plane? But why 1 mm, and not 1.5 mm, or 2 mm? I should say that if those points really do represent stars in the Milky Way, a difference of 0.5 mm represents hundreds of light years.
  17. Nov 22, 2009 #16
    Thank you, ideasrule, for the confirmation and the scatterplot. Is it safe to say then that reports about the solar system being several dozen light years north of the galactic "plane" (or having just been passing through it from 98 to 2016)...are basically gibberish? Or are we missing something? Has something floating around been misinterpreted?
    [floating around the internet, that is, not space]
  18. Nov 22, 2009 #17


    User Avatar
    Science Advisor
    Homework Helper

    The solar system will (or has) pass through the galactic plane.
    But it depends if you mean the Galactic plane as defined by the galactic coordinate system (which were based on 100year old observations and are slightly wrong) or the best estimate of the plane as of today or actual plane of the galaxy which constantly changes and we don't accurately measure.

    Either way it has no effect on the earth.
  19. Dec 2, 2009 #18
    The topic of crossing the "galactic plane", coinciding with the Mayan calendar, and the catastrophe of "world's end in 2012" are a mixed muddling of mythology.

    The Mayan calendar comes to an end (in linear counting mode) in 2012. However, the calendar itself is a circle and the Mayans thought in this circular pattern, much the same way astrology and the Chinese calendar are cyclic patterns.

    Crossing the galactic plane is speculation, but also a cyclic event. Much is still unknown about the electrical nature of the cosmos as far as "action at a distance". The concern from some theorists is that the "plane" transit is related to our magnetic field shift, which is also a cyclic pattern. Since we've only inhabited this rock as semi-sentient beings for a short time, we have yet to experience that effect first-hand.

    Hard data is difficult to find and there is a lack of consensus among those who are "supposed" to know these things...

    I'm just a knucklehead...

  20. Dec 2, 2009 #19


    User Avatar
    Science Advisor
    Homework Helper

    It doesn't end it just clocks around a new leading digit (from 12 to 13), it last did this in the 17th century and nothing happened.

    Not speculation, our orbit around the galaxy is inclined - we must cross the plane twice in each rotation.

    Apart from the complete lack of any mechanism to link these, the galactic orbit period is 220Myr and very regular.
    Magnetic field reversals are not at all regular (and are probably chaotic) but occur at an interval of < 1Myr.

    But lots of other species have and don't seem to have been over worried.
  21. Dec 27, 2009 #20
    Have you ever looked out into the night sky and seen the Milky Way Galaxy? Did you notice the obvious tilt? It is at a steep angle to the straight line of the horizon. Why? It turns out that our solar system appears to belong to another galaxy that is colliding with the Milky Way. This was recently discovered when scientists were trying to figure out sources for "Dark Matter" that would account for forces we can measure but not see visibly. Using near-infrared a huge sister galaxy circling the Milky Way was discovered. It's called the Sagittarius Dwarf Galaxy,(SGR for short). For those keen on the 2012 data, this is the reason our entry point to the rift, center, heart of the Milky Way is thru Sagittarius. The two collide at this point. This explains why our solar systems is at a angle to the plane of the galaxy and why we dip above and below that center line every 12,000 years or so. After slow, continuous gnawing by the Milky Way, Sagittarius will be whittled down to the point that it cannot hold itself together much longer!
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?