Jump to content


Photo
- - - - -

Orientation of Solar System


26 replies to this topic

#1 Essay

Essay

    Explaining

  • Members
  • 793 posts

Posted 23 December 2008 - 08:01 PM

Some time ago I figured our solar system was oriented a certain way as it traveled around the galaxy.
I don't even recall how now, but....
Does anyone know of a link or have other info. or opinion?

IMHO
The plane of our solar system is perpendicular to the plane of the Milky Way, and perpendicular to our direction of travel--towards the South.

I suppose that would be the South Pole of the Sun (assuming it roughly aligns with our South Pole) pointing toward our direction of travel around the galaxy.
Do those two perpendiculars define enough of a frame?

Any help will be appreciated.

Thanks,
~SA

#2 Turtle

Turtle

    Member

  • Members
  • 14,866 posts

Posted 24 December 2008 - 02:54 AM

Some time ago I figured our solar system was oriented a certain way as it traveled around the galaxy.
I don't even recall how now, but....
Does anyone know of a link or have other info. or opinion?
...
Any help will be appreciated.

Thanks,
~SA


Funny, but in poking into the galactic plane in another thread on the solar system above/below galactic plane, I kinda guess I felt as you, that they were more-or-less parallel. It wasn't pertinent there, but you got a poser here for sure now. My curiosity piqued, I found us theses: ;) :shrug: :)

IRAS View Of The Milky Way Galaxy

PHY 445/515: Coordinate Systems

The galactic equator is inclined to the celestial equator by 62.6o.



#3 Essay

Essay

    Explaining

  • Members
  • 793 posts

Posted 24 December 2008 - 03:56 AM

Parallel? Did you mean perpendicular?
===

Cool Pic!
from: IRAS View Of The Milky Way Galaxy
"The hazy, horizontal S-shaped feature that crosses the image is faint heat emitted by dust in the plane of the solar system."

Yes, that blue line is at ~60 degrees! Not quite the 90 degrees I thought it was, but still far from parallel.
===

PHY 445/515: Coordinate Systems
"The ecliptic coordinate system is based on the apparent Solar orbit, and is the natural system for Solar System studies.... The inclination of the ecliptic with respect to the celestial equator is 23 degrees."

Shouldn't that 23 degrees be added onto the 62 degrees (Earth's angle) to get the angle of the solar system to the galactic plane?

But it looks like 60ish degrees.
Maybe that's a mistake, and they should be saying "The galactic equator is inclined to the celestial ecliptic equator by 62.6 degrees." ;)

...or does it just "look" that (62 degrees) way because it's photographed from earth?
...and the galactic equator would be inclined ~86 (62.6+23.3) degrees to the ecliptic equator? :)
===

Any info. on direction of travel (Southern Hemisphere forward?)?
===

Great links: Thanks,

~ :shrug:

#4 Turtle

Turtle

    Member

  • Members
  • 14,866 posts

Posted 24 December 2008 - 01:27 PM

Parallel? Did you mean perpendicular?

Uhm...erhm...I don't think so? :hyper: I had it in my mind that the axes through the galactic plane & solar plane were parallel. :earth: :)
===

Cool Pic!
from: IRAS View Of The Milky Way Galaxy
"The hazy, horizontal S-shaped feature that crosses the image is faint heat emitted by dust in the plane of the solar system."

Yes, that blue line is at ~60 degrees! Not quite the 90 degrees I thought it was, but still far from parallel.
===


Shall we say, "not aligned" as we thought? Picture's worth a thousand words at any angle. :hihi:

PHY 445/515: Coordinate Systems
"The ecliptic coordinate system is based on the apparent Solar orbit, and is the natural system for Solar System studies.... The inclination of the ecliptic with respect to the celestial equator is 23 degrees."

Shouldn't that 23 degrees be added onto the 62 degrees (Earth's angle) to get the angle of the solar system to the galactic plane?

But it looks like 60ish degrees.
Maybe that's a mistake, and they should be saying "The galactic equator is inclined to the celestial ecliptic equator by 62.6 degrees." :shrug:

...or does it just "look" that (62 degrees) way because it's photographed from earth?
...and the galactic equator would be inclined ~86 (62.6+23.3) degrees to the ecliptic equator? :confused:
===


I puzzled over this awhile when reading the link. I think the explanation is in this part (boldening mine):

Ecliptic Coordinates
The ecliptic coordinate system is based on the apparent Solar orbit, and is the natural system for Solar System studies. The equator (the ecliptic) is the plane of the terrestrial orbit, projected onto the celestial sphere. The poles are projections of the Earth's orbital poles. Coordinates , are measured in degrees. The inclination of the ecliptic with respect to the celestial equator is

23o26'21".448 - 46".82T - 0".0006T2 + 0".0018T3,
where T in the number of Julian Centuries from 2000AD. The origin is the same as that of the celestial system. The north ecliptic pole is located at 18h +66o33' in celestial coordinates. Conversion from ecliptic to celestial coordinates involves only a rotation of the sphere. ...


Any info. on direction of travel (Southern Hemisphere forward?)?
===

Great links: Thanks,

~ :)

Nothing that I have seen yet on who leads, N or S.

My pleasure; thanks for interesting questions. I think we can worry this bone a bit more before we bury it, eh? :dog: :eek2: :turtle:

#5 Essay

Essay

    Explaining

  • Members
  • 793 posts

Posted 24 December 2008 - 02:40 PM

Lunchtime again: gotta run now

The origin is the same as that of the celestial system.

Do they mean in terms of T?
===

They say:
"The poles are projections of the Earth's orbital poles."
I take this to mean the poles projected up from a plane through our inscribed orbit (not through our planets equator). So wouldn't this be pretty much the same as the sun's poles?

...except for the

Earth — Inclination: Reference (0) (7.25° to Sun's equator)
According to Earth - Wikipedia, the free encyclopedia - More sources »


So would that 7.25 get added onto the 86 degrees or subtracted from it, I wonder?
===

I admit that as my first impression (metaphor) of the solar system and galaxy, I imagined them as parallel; but as my first post said, years ago something made me figure that they were perpendicular ...and traveling South.

But I still think the solar ecliptic is tilted up around 90 degrees relative to the galactic equator.

Earth's orbit is tilted ~7 degrees relative to the solar ecliptic and the planet is tilted ~23 degrees relative to that orbit, but I don't know if they have an additive or cancelling effect relative to the solar ecliptic.

But whichever, I think that is why that blue band of the solar system appeared (from Earth) to be offset by about 30 degrees from the galactic perpendicular.

Thanks for the help :),

~ :confused:

#6 Turtle

Turtle

    Member

  • Members
  • 14,866 posts

Posted 24 December 2008 - 05:03 PM

Lunchtime again: gotta run now
Do they mean in terms of T?

I haven't a clue. :turtle:
===

They say:
"The poles are projections of the Earth's orbital poles."
I take this to mean the poles projected up from a plane through our inscribed orbit (not through our planets equator). So wouldn't this be pretty much the same as the sun's poles?


Again, not sure. I think the ecliptic is more-or-less a mean because none of the planets orbit in the same plane? Perhaps our focus ought go to this: PHY 445/515: Coordinate Systems

The origin [of the ecliptic] is the same as that of the celestial system.


I admit that as my first impression (metaphor) of the solar system and galaxy, I imagined them as parallel; but as my first post said, years ago something made me figure that they were perpendicular ...and traveling South.

But I still think the solar ecliptic is tilted up around 90 degrees relative to the galactic equator.

Earth's orbit is tilted ~7 degrees relative to the solar ecliptic and the planet is tilted ~23 degrees relative to that orbit, but I don't know if they have an additive or cancelling effect relative to the solar ecliptic.

But whichever, I think that is why that blue band of the solar system appeared (from Earth) to be offset by about 30 degrees from the galactic perpendicular.

Thanks for the help :),

~ :hyper:


The picture says it all for me; except of course which pole leads still. :shrug: Whether 30º or 60º, it's 30º, 60º, 90º all around and that is rather interesting to note in its own right. :confused:

#7 modest

modest

    Creating

  • Members
  • 4,959 posts

Posted 12 January 2009 - 04:42 PM

The picture says it all for me; except of course which pole leads still. :)


I think that 90 degrees longitude (l=90) in the galactic coordinate system is the direction of galactic rotation. The constellation Cygnus resides there. Toward Cygnus would then be the direction of galactic rotation from our point of view. As Cygnus resides in our northern earthly hemisphere (and by extension, the solar northern hemisphere), I believe the north pole of the earth and sun should lead our motion of galactic rotation.

A person sitting on the north pole of the earth would be able to see where the solar system is heading (toward the direction of Cygnus), while a person sitting on the south pole could not.

Rotation image 1
Rotation image 2

Galactic longitude is measured in degrees as well from 0° to 360° originating in the direction of the axial center of the Milky Way in the constellation Sagittarius. Traveling around the galactic equator we find Cygnus at 90°,

Galactic Coordinate System



#8 Turtle

Turtle

    Member

  • Members
  • 14,866 posts

Posted 12 January 2009 - 04:56 PM

I think that 90 degrees longitude (l=90) in the galactic coordinate system is the direction of galactic rotation. The constellation Cygnus resides there. Toward Cygnus would then be the direction of galactic rotation from our point of view. As Cygnus resides in our northern earthly hemisphere (and by extension, the solar northern hemisphere), I believe the north pole of the earth and sun should lead our motion of galactic rotation.

A person sitting on the north pole of the earth would be able to see where the solar system is heading (toward the direction of Cygnus), while a person sitting on the south pole could not.

Rotation image 1
Rotation image 2


Roger. Now just to check here, because your second diagram is a bit confusing in this regard, the solar system is orbiting the galactic center counter-clockwise, oui/no? :)

Also, your last link affirms the above-the-galactic-plane assertion we came to here & elsewhere. >> NationMaster - Encyclopedia: Galactic coordinate system

...Our solar system lies 112.7±1.8 light years (34.56±0.56 pc) [1] above the central plane of the Milky Way. ...



#9 belovelife

belovelife

    psionicist - preserver lv.143

  • Members
  • 1,397 posts

Posted 12 January 2009 - 04:58 PM

i personally think that the center of the galaxy (black hole)
alighns the entire galaxy using 3 fields
1-gravity
2-magnetism
3-bend in space time
for 3, the "north and south poles of the black hole"
are inverses of eachother
whereas, given north would expand spacetime
given south would shrink spacetime
then the nuetral area would be the disc that we typically see
the north side expands to alighn the matter on that side
with the correlating side of the disc
because of the shrink of spacetime on the south
it funnels all the matter into a stream that appears to be particles

#10 modest

modest

    Creating

  • Members
  • 4,959 posts

Posted 12 January 2009 - 05:12 PM

Roger. Now just to check here, because your second diagram is a bit confusing in this regard, the solar system is orbiting the galactic center counter-clockwise, oui/no? :)


Yes, I believe so. Clockwise in both pics. And, I should probably clarify (or at least give credit) the diagrams were not made by me, but came from this amateur radio astronomy type web page. But, I think, yes, the way the spirals are drawn in the second diagram would mean rotation would have to be clockwise.

~modest

EDIT: Wops, you said "counter-clockwise". I guess then, I disagree. Or, one of us is confused :sherlock:

#11 freeztar

freeztar

    Pondering

  • Members
  • 8,432 posts

Posted 12 January 2009 - 06:17 PM

In all honesty, I'm still trying to make sense of all this, but I thought a comment was in order.

It seems to me that the rotation is clockwise. In other words, the "galactic arms" should be trailing rather than leading.

#12 belovelife

belovelife

    psionicist - preserver lv.143

  • Members
  • 1,397 posts

Posted 12 January 2009 - 06:30 PM

i wonder what happens when 2 galaxies arms dance and hold hands :)

#13 Turtle

Turtle

    Member

  • Members
  • 14,866 posts

Posted 12 January 2009 - 07:01 PM

Yes, I believe so. Clockwise in both pics. And, I should probably clarify (or at least give credit) the diagrams were not made by me, but came from this amateur radio astronomy type web page. But, I think, yes, the way the spirals are drawn in the second diagram would mean rotation would have to be clockwise.

~modest

EDIT: Wops, you said "counter-clockwise". I guess then, I disagree. Or, one of us is confused :)


OK We have to resolve this. :eek2: Neither of your two diagrams specify up or down view or which pole is which.

"Get a Straight Answer"

... As for the rotation of the Earth... you should first of all realize that "clockwise" and "counter clockwise" are not absolute properties, but depend on your point of view. Imagine a clock with a transparent face, with you watching it from the rear. The number 12 is still on top and 6 still on the bottom, but now 3 is on the left and 9 on the right. So when the clock hand moves from 12 to 3, it moves ... counterclockwise!

To define rotations with no ambiguity, we can stipulate they are always observed from the NORTH, from some point far above the north pole of the Earth. ...


The more scholarly articles I've been off hunting simply don't seem to mention the direction, but I just found this answer for counter-clockwise. I honestly thought everything rotated counter-clockwise because of conservation of angular momentum? :sherlock: :singer:

Google Answers: In what direction does the Sun travel relative to the calendar year?

The Sun is indeed in motion. It orbits the center of our galaxy at
the speed of approx 155 miles per second in a counter-clockwise
direction. And of course we are moving right along with it, being
"dragged" as you put it.

It takes the Sun (and us) about 200 - 250 million years to orbit once
around the center of the Milky Way Galaxy. So yes, the Sun does have
a "year" as well - about 200 million times or so as long as an Earth
year. ...



#14 modest

modest

    Creating

  • Members
  • 4,959 posts

Posted 12 January 2009 - 08:16 PM

OK We have to resolve this. :eek2: Neither of your two diagrams specify up or down view or which pole is which.

"Get a Straight Answer"


No. They do not. (and by the way, this conversation seems so oddly familiar :))

The only things for certain the diagrams show is that rotation is going towards Cygnus from our point of view. That is to say: if you are looking at the constellation Cygnus then you are looking toward the direction the solar system is moving in terms of galactic rotation. It's the fact that Cygnus is in the northern hemisphere that settles the question of which pole leads. It is the north pole.


The more scholarly articles I've been off hunting simply don't seem to mention the direction, but I just found this answer for counter-clockwise. I honestly thought everything rotated counter-clockwise because of conservation of angular momentum? :phones: :earth:


Astrnomical systems do usually rotate counterclockwise as a matter of convention. The right hand rule is usually used. If you point your thumb up then that defines the north pole. Your fingers then (not pointed straight out, but curved a bit) show the direction of rotation. Point your thumb at your face and look at the direction your fingers are pointing and it is indeed counterclockwise.

The direction of rotation usually defines the pole in this way. Looking at things from the top then (from the north—which is also convention) will show counterclockwise rotation.

The diagrams I linked obviously don't follow this convention. But, the pertinent thing is that the galactic coordinate system has Cygnus at 90 degrees which is the direction of rotation (as viewed by us). So if we are on earth's (or the sun's) north pole and looking up, we will see the general direction that we are rotating toward.

Is this much more than gibberish?

~modest

#15 modest

modest

    Creating

  • Members
  • 4,959 posts

Posted 12 January 2009 - 08:18 PM

It seems to me that the rotation is clockwise. In other words, the "galactic arms" should be trailing rather than leading.


I agree. The diagrams both show clockwise rotation as I see it.

~modest

#16 Turtle

Turtle

    Member

  • Members
  • 14,866 posts

Posted 12 January 2009 - 09:20 PM

So, summing up in more colloquial terms, the Solar System is rotating around the Galactic Center in a counter-clockwise direction when viewed from above the North Galactic Pole. Additionaly, when viewing the Solar System from the the side of the Milky Way with North up, the Solar System Plane in its elliptical orbit of the Galactic Center is inclined to the Galactic Plane, leading with its North Pole(s), and above the Galactic Plane moving North.

All good? :phones:
:eek2:
:earth:


#17 modest

modest

    Creating

  • Members
  • 4,959 posts

Posted 13 January 2009 - 09:28 AM

Damn Turtle, I think you've given me a brain hemorrhage.

I think... perhaps... just maybe... you've got your up and down backwards. Or, perhaps the astronomical community has their galactic coordinate system backwards. Or, perhaps I'm turned around... something has gotten turned around :)

Ok, starting over...

I don't think the galaxy rotates counterclockwise as viewed from the north galactic pole. I think it rotates clockwise as viewed from north. I don't think it follows the right hand rule (at least, not in the galactic coordinate system). A paper, such as this:

The Sun's Distance Above the Galactic Plane

which uses the galactic coordinate system would seem to be saying that we are above the ecliptic as is defined by that coordinate system. And I'm pretty sure, that according to that system, viewing the galaxy from the north galactic pole would show clockwise rotation.

Posted Image
-source

The above pic would have the galaxy rotating clockwise as viewed from the north. A positive latitude (above the galactic plane) would then be above the disc (as viewed from the side) where the disc is rotating left.

I have a suspicion of why the GCS doesn't follow the normal right hand rule. If it did then earth's north pole would point to the south side of the galaxy. In order to have earth's north and the galaxy's north roughly the same direction, the left hand rule is used. But, that's just a suspicion—I don't know if that's the reason. Nevertheless, as the pic above shows it, the galaxy does rotate clockwise as viewed from the north. It rotates in the direction of 90 deg. longitude.

Yes / no / maybe???

~modest



Reply to this topic