Solar System's motion through galaxy

[JarodRussell]

As you may or may not know, our solar system is in motion. It revolves around the center of the galaxy at 220 km/s in roughly 240 million years. It also oscillates 'up' and 'down' perpendicular to the galactic 'disc' with a period of about 70 million years. That much I knew.

BUT today someone insisted that our sun actually moves through all four spiral arms of our galaxy, instead of staying in place while the entire thing revolves around itself. And I went . Is that actually true? I thought the solar system would stay forever in the Orion Arm.

 

[Robert D. Robot]

I had also read that our solar system moves on it's own independent "orbit"/trajectory around the center of our galaxy which does eventually take "us" from one arm to another, but I had not read that we oscillate "up and down" relative to the galactic plane. The same article theorized that -while we are somewhat protected during the periods that we are within an arm- we are more exposed during our transits between arms, which may explain some of the periodic extinction events.

I wish I could remember where/when I read this to provide a reference, but I am blanking (AND I am leaving here shortly for the evening....). I trust someone with more knowledge will come in and add their 2¢, and I am looking forward to hearing more on the subject!

 

[Asbo Zaprudder]

I had also read that our solar system moves on it's own independent "orbit"/trajectory around the center of our galaxy which does eventually take "us" from one arm to another, but I had not read that we oscillate "up and down" relative to the galactic plane. The same article theorized that -while we are somewhat protected during the periods that we are within an arm- we are more exposed during our transits between arms, which may explain some of the periodic extinction events.

I wish I could remember where/when I read this to provide a reference, but I am blanking (AND I am leaving here shortly for the evening....). I trust someone with more knowledge will come in and add their 2¢, and I am looking forward to hearing more on the subject!

The Galactic Cycle of Extinction

 

[The Mirrorball Man]

Makes you feel sort of insignificant, doesn't it?
[yt]http://www.youtube.com/watch?v=NQu_RRLbVDA[/yt]

 

[YellowSubmarine]

I'm not certain if it moves through the arms, but I know for sure that some neighbouring stars moving a lot relative to us, and I learnt this when I checked the projections of which stars will the two Voyagers pass by. Slightly hard to find, because searching for "star voyager" gets me results for some American show I haven't heard about.

http://en.wikipedia.org/wiki/AC%2B79_3888

All other stars move too so they are eventually going to change as well, albeit much slowly than that. The Sun moves at 20 km/s relative to the average speed of our neighbours (10% of the speed we have around the centre of the galaxy), I guess that probably translates to moving through the arms.

 

[JarodRussell]

As of now, I found three versions/theories.

a) solar system doesn't move at all, relative to the arms
b) solar system crosses all arms while it orbits the center of the galaxy
c) solar system just goes 'back' and 'forth' inside the Orion Arm, but never crosses other arms.

and d) there are no spiral arms.

Now what?

 

[Robert Maxwell]

The Orion Arm itself (which is a minor arm, not a major one) passes through a major arm every 100 million years or so, taking us along with it. It takes about 10 million years for us to pass through a major arm.

Also, it is believed the Milky Way is a barred spiral galaxy.

 

[YellowSubmarine]

Now what?

Well, we can just introduce a new option and go with it:

e) There is no galaxy!




Other than that, option a) seems like an almost certain impossibility, given the relative motion of the rest of the stars it would be quite crazy that we are the stationary star.

 

[JarodRussell]

Other than that, option a) seems like an almost certain impossibility, given the relative motion of the rest of the stars it would be quite crazy that we are the stationary star.

What was meant by that is that the sun is merely "dragged" along. There's still relative motion between the individual stars. But in contrast to b) and c), it doesn't oscillate back and forth or move through the arms.

 

[RoJoHen]

Other than that, option a) seems like an almost certain impossibility, given the relative motion of the rest of the stars it would be quite crazy that we are the stationary star.

What was meant by that is that the sun is merely "dragged" along. There's still relative motion between the individual stars. But in contrast to b) and c), it doesn't oscillate back and forth or move through the arms.

It probably does move through the arms, but then again, most other stars systems probably do too.

 

[Asbo Zaprudder]

For about 50 years, galactic spiral arms have been understood not to orbit in the same sense as individual stars do around the galactic centre. There are a few competing theories, not all necessarily mutually exclusive invoking density waves, solitary waves (solitons), stochastic self-propagating star formation, and the latest involving gravitationally aligned orbits:

Origin of the spiral structure

The Anatomy of Spiral Arms

 

[Nerys Ghemor]

Also, it is believed the Milky Way is a barred spiral galaxy.

This was news to me when I read it in an astronomy book a few weeks ago. When I was younger I'd always heard that we were just a "normal" spiral galaxy and that a barred spiral was an exotic type different from ours.

It seems a lot of popular depictions of the Milky Way in various media are due for an overhaul.

 

[SPCTRE]

<cue 'fascinating' GIF>

Color me intrigued.

 

[Wanderlust]

The sun and other stars move in and out of the spiral arms. The arms are more like density waves, objects move in and out of them.

Here is what we look like. Now only 2 major arms with a variety of spurs.

I know im fascinated by this too, i learned we were a normal spiral but then discovered we were barred only a year ago. Funny, we've known about the bar since the 90s. The dipictions of a bar are starting to trickle in though.

i cant believe it either.. were a frikin bar.. i love it!

Note what shape they give our galaxy in this video
http://www.youtube.com/watch?v=5HVb4YRsDIg

 

[Nerys Ghemor]

I always thought, when I saw it in science books, that the barred spiral was a remarkable, elegant design. The shape even became one of the things I enjoyed doodling in class when I got bored. Finding out that we are one was mindblowing because I think of them as being so beautiful.

And that's a neat video! And yep...I see the bar there. That wonderful scene in The Wounded Sky where...

Spoiler: The Wounded Sky

Kirk jumps outside of the Milky Way and sees our own galaxy for the first time from the outside

...will look very different in my head from now on.

Speaking of galaxies...I'm about to ask a dumb question here, but are we able to zoom in on the Magellanic Clouds or even Andromeda enough, to be able to map the stars in them?

 

[Asbo Zaprudder]

Speaking of galaxies...I'm about to ask a dumb question here, but are we able to zoom in on the Magellanic Clouds or even Andromeda enough, to be able to map the stars in them?

It's not so much a matter of magnification, but of light-gathering power. We can easily detect the light from individual highly luminous stars in other galaxies (for example, the Cepheid variables whose periodicities in brightness are one way of establishing distance) but dimmer dwarf stars like the Sun take very long exposure times. Mapping is possible but the error bars are large when estimates of a star's absolute magnitude are used to measure distance.

 

[Deckerd]

I know the video only used a few galaxies for size comparison but doesn't it strike you how beautiful our galaxy is compared to others?

 

[Asbo Zaprudder]

That's only an artist's impression. We don't really have much more than a vague notion of what our galaxy would look like from outside. Also, to the naked eye, it would look exceeding dim if we could view all of it at once -- much like the Andromeda galaxy seems nothing more than a faint smudge of light.

 

[Deckerd]

Stop being a killjoy.

 

[Asbo Zaprudder]

Stop being a killjoy.

Sorry.