Our Galactic Plane

[Turtle]

Often in popular science programs a description of our galaxy, the Milky Way, is given as some preface to an Earth related matter of astronomy. Most recently I heard a speaker give a partial, albeit incomplete, description of the Milky way that was accurate inasfar as it was the view from above/below whein one see the spiral arms.

 

Without going on to clarify that from the edge-on view the Milky Way has a bulge in the center and the 'arms' thin considerably the further they get from the center, the speaker went on then talking about the 'galactic plane'. The lecture criticizing aside, I heard the statement that our solar system is about to cross the galactic plane, and I haven't turned up any bona fide links yet to confirm that.

 

Now I best clarify :hyper: , so the galactic plane is the imaginary plane projected through the galactic center and parallel to the galactic equator, our solar system is out near the edge of an arm/spoke and rotating around the galactic center, while at the same time moving up and then down across the galactic plane. (I will post the periodicity of those movements as soon as I find them. )So, a Brotherly Biscuit of gratitude for any and all who can find a bona fide link that establishes our current position and direction in relation to the Milky Way's galactic plane. :computerkeys: (I'm still looking myself of course.;) ) :cup:

[InfiniteNow]

Not sure if this will get you what you are after, but it's fun all the same. It's a free downloadable atlas of the universe provided by the Hayden Planetarium:

 

About the Digital Universe | Digital Universe Atlas | Hayden Planetarium

Since 1998, the American Museum of Natural History and the Hayden Planetarium have engaged in the three-dimensional mapping of the Universe. This cosmic cartography brings a new perspective to our place in the Universe and will redefine your sense of home.

 

The Digital Universe Atlas is distributed to you via packages that contain our data products, like the Milky Way Atlas and the Extragalactic Atlas, and requires free software allowing you to explore the atlas by "flying" through it on your computer.

 

 

My god, it's full of stars. :computerkeys:

 

 

 

 

Looking back on the Milky Way from M54, a globular cluster that's 85,000 light-years from Earth.

[Turtle]

Not sure if this will get you what you are after, but it's fun all the same. It's a free downloadable atlas of the universe provided by the Hayden Planetarium:

 

About the Digital Universe | Digital Universe Atlas | Hayden Planetarium

 

My god, it's full of stars. :)

 

 

Sweet! Did you download it? I can't download anything without permission as this is not my computer, but if you downloaded it by all means let me know if it answers my question. I'm still searching....:) :)

[InfiniteNow]

Facing the same problem. Must have admin password (which I do, but would get into some heat if used). I'll see if I can check out it out on my girlfriend's computer next time I'm at her palce... Problem is, she's always at mine. :Patience: :)

[Turtle]

Facing the same problem. Must have admin password (which I do, but would get into some heat if used). I'll see if I can check out it out on my girlfriend's computer next time I'm at her palce... Problem is, she's always at mine. :Patience: :)

 

Acknowledged. I found this quirky tidbit searching the phrase Web Search Results 1 - 10 of about 29,700 for 'Where is Earth in relation to the galactic plane?'

 

American College of Orgonomy - Celestial Motion (Part I): A Lawful Relationship Between the Rotation Of the Planets and the Galactic Plane

 

The author gives no hard data on current state, describes planetary/solar- system motion relative to the galactic plane as '... carried along like rolling balls on progressing water waves,...', and seems to talk about aether.

 

At any rate, the search goes on; is Earth above or below the Galactic Plane right Now? Is Earth approaching or receding from the Galactic Plane right Now? What is the periodicity of the cycle? :) :)

[Pyrotex]

I take my one and only trip

On the Galactic Plane.

I stare out the window.

The stars look so far away.

[Turtle]

I take my one and only trip

On the Galactic Plane.

I stare out the window.

The stars look so far away.

 

But failing fare

I missed the train,

and pon my window,

dayly rain.

 

Knowing how much everyone loves Wicky, ;) I have found some data there...alas it only gives the periodicity for our solar system's trip around the galaxy.

It would take the solar system about 226 million years to complete one orbit ("galactic year"), and so is thought to have completed about 25 orbits during its lifetime. The orbital speed is 217 km/s, i.e. 1 lightyear in about 1,400 years, and 1 AU in 8 days.

Solar apex - Wikipedia, the free encyclopedia

 

Aha! But it led me to this:

Our sun is also in motion. Relative to the average motion of the most commonly measured nearby stars, the sun moves with a speed of about 16.5 kilometers per second, or nearly 50 light-years per million years. The sun's path is inclined about 25 degrees to the plane of the galaxy and is headed toward a region in the constellation of Hercules near its border with Lyra. The sun oscillates through the plane of the galaxy with an amplitude of about 230 light-years, crossing the plane every 33 million years. However, the sun's motion relative to the local stellar neighborhood should not be confused with its movement around the center of the galaxy, since the whole solar neighborhood (including the sun) orbits the galactic center once every 250 million years. Just as we do not include the earth's velocity around the sun when calculating the speed of an airplane (we are only interested in the ground-speed), astronomers do not include the sun's galactic orbital velocity when describing its local motion.

American Scientist Online - The Galactic Environment of the Sun

 

Well, off to read the whole paper as we have the periodicity now but I haven't found the current state info.. :hihi: :cup:

[Eclogite]

However in a letter to Nature (Periodic mass extinctions and the Sun's oscillation about the galactic plane) these astronomers note the periodicity to be 26 million years.

In another letter to Nature (The Sun's motion perpendicular to the galactic plane) we are told "For all the models we consider, the most recent passage of the Sun through the galactic plane occurred in the past 3 Myr provided only that the present position of the Sun is between 0 and 20 pc above the plane."

 

Please note that the full cycle is double whatever of the above figures we go with.

[Turtle]

However in a letter to Nature (Periodic mass extinctions and the Sun's oscillation about the galactic plane) these astronomers note the periodicity to be 26 million years.

In another letter to Nature (The Sun's motion perpendicular to the galactic plane) we are told "For all the models we consider, the most recent passage of the Sun through the galactic plane occurred in the past 3 Myr provided only that the present position of the Sun is between 0 and 20 pc above the plane."

 

Please note that the full cycle is double whatever of the above figures we go with.

 

Great info Eclogite! :hyper: I could only read the Abstracts, but it's enough to get the sense no one has as precise a measure of our location as some have suggested. To whit, the guy I heard talking that prompted this thread was claiming our solar system was going to cross the galactic plane in 2012.

 

So we only know our perpindicular position to within 20 pc (parsecs, right?) and our distance from the center of the galaxy within 10,000 light-years, so anyone claiming knowledge of a precise time of our crossing is exagerating the facts...yes?

 

But still, even the Nature blurb seems to allow enough error that we could still be approaching the glactic plane. The game's still afoot then, if for no other reason than no one seems to have said if we are now above, or below the galactic plane. Then there's that haunting nasty business of extinction, and while the Nature articles have it correlated to the galactic plane, the article I got the 33 million year cycle from correlated extictions to our position in relation to the Local Bubble.

...The sun is on the edge of what is sometimes called the Local Bubble, a great void in the distribution of interstellar gas in the nearby galactic neighborhood.

American Scientist Online - The Galactic Environment of the Sun

 

Plane it may be, simple it is not.

[freeztar]

Interesting thread...

 

So have there been any new developments? :eek2:

 

Where the heck are we? :phones:

[Turtle]

Interesting thread...

 

So have there been any new developments? :(

 

Where the heck are we? :doh:

 

Indubitably! :phones:

 

None I am aware of. :cup:

 

Quite simply, we are lost in space. :eek2:

[Qfwfq]

Quite simply, we are lost in space.

We?

 

I'm not! I know exactly where I am. I'm sitting right here, on a chair, in front of this PC, in a room at a customer's place in Mestre, near the shores of the Venice lagoon...

 

:phones:

[Turtle]

We?

 

I'm not! I know exactly where I am. I'm sitting right here, on a chair, in front of this PC, in a room at a customer's place in Mestre, near the shores of the Venice lagoon...

 

:)

 

Aha! A zenith. Tant mieux. Taking your upward view, do you see any authoritive reference we have missed that assuredly establishes our Solar system's orientation/situation in regards to the plane of the Milky Way? Over...;)

[modest]

In:

 

“The Sun's Displacement from the Galactic Plane from Spectroscopic Parallaxes of 2500 OB Stars”

 

B. Cameron Reed uses a “model independent” method to get 19.6 (+/-) 2.1 pc from the galactic plane.

 

The paper also has a table of other determinations of the distance from other sources.

 

I also found this interesting:

 

“Variable Oort Cloud Flux Due to the Galactic Tide”

 

Comparing craters in the geological record to the galactic tide of the ecliptic having an effect on the oort cloud. It sounds very reasonable to me.

 

-modest

[Turtle]

In:

 

“The Sun's Displacement from the Galactic Plane from Spectroscopic Parallaxes of 2500 OB Stars”

 

B. Cameron Reed uses a “model independent” method to get 19.6 (+/-) 2.1 pc from the galactic plane.

 

The paper also has a table of other determinations of the distance from other sources.

 

I also found this interesting:

 

“Variable Oort Cloud Flux Due to the Galactic Tide”

 

Comparing craters in the geological record to the galactic tide of the ecliptic having an effect on the oort cloud. It sounds very reasonable to me.

 

-modest

 

Thanks Modest! The first paper agrees with our previous findings putting our position within ~20 parsecs.

 

The second is indeed interesting, if not an outright peach. I think one of the earlier references here hinted at something similar. Anyway, here's the juicy fruit. >>

... The peak flux times lag the Galactic plane crossing times by ~ 2 Myr and are not precisely periodic because of decreasing Galactic density as the Sun recedes from the Galactic core. The phase of the oscillations is restricted by observations which place the last previous plane crossing at ~ 1.5 Myr in the past (and the next flux peak ~ 1 Myr in the future).

 

... Figure 3 shows the results for oscillation models having a

range of plane crossing periods from 25-45 Myr. ...

 

Looks like we're out of the woods as far as large comet impacts on Earth for the 1,000,000 years or so. :hihi: My only question now is are we above or below the galactic plane, as none of the sources make mention of it. :cup: :ud:

[modest]

My only question now is are we above or below the galactic plane, as none of the sources make mention of it. :cup: :ud:

 

Would Z⊙ be negative below the galactic plane? I guess not because it’s a distance and not a latitude in the Galactic coordinate system. In any case:

 

"The Sun's Distance Above the Galactic Plane"

 

indicates (first paragraph of introduction) that we are above or ‘north’ of the plane. I guess it's in the title of the paper too :cup: This would be up if you were facing the direction of galactic rotation (clockwise from north) with the galactic center on your right.

 

This thread keeps reminding me of: The Galaxy Song by Monty Python http://www.youtube.com/watch?v=Z2JU4gX6rg8 :hihi: :)

 

-modest

[Turtle]

In any case:

 

"The Sun's Distance Above the Galactic Plane"

 

indicates (first paragraph of introduction) that we are above or ‘north’ of the plane. I guess it's in the title of the paper too :hihi:

 

Very nice. Before moving to why should North be up, there is a telling bit in the paper regards getting oriented.

... The equatorial plane of the galactic coordinate system' date=' as adopted by the IAU General Assembly in 1958, by definition passes through the Sun. If the Sun were exactly in the midplane, the origin of the galactic coordinate system should coincide with the galactic center. However, it has been shown that the coordinates of Sgr A* imply that the Sun is actually slightly above the plane.[/quote']

 

So the equatorial plane of the galactic coordinate system is not the equatorial plane of the galaxy; yes/no? Interesting they make no mention of change in Z, but their ~20 parsec measure is in accord with the others we have rooted out.

 

This would be up if you were facing the direction of galactic rotation (clockwise from north) with the galactic center on your right.

 

;) Errrhmmm... Since our North is 'up', or 'top', then the galactic top is more-or-less having the same up. Now since the up/down choice is necessary but arbitrary, is there any compelling cultural or other social influence that may have lead to our choice? :)

 

This thread keeps reminding me of: The Galaxy Song by Monty Python :) :)

 

-modest

 

Oh yeah! I love the full Monty! :D