by neufer » Tue Apr 18, 2017 4:23 am
Chris Peterson wrote:geckzilla wrote:Ann wrote:
As for Milky Way's dust lane, it will certainly be mostly unchanged a million years from now. The Milky Way has a thick dust lane, and a million years is almost nothing in the life of a galaxy - at least if the galaxy in question isn't undergoing a major merger in that time. And ours won't, not in just a million years!
I'm not sure we know enough to say that for certain. Dust is just as dynamic as stars and some parts change a lot while other parts aren't undergoing much change. A million years might be plenty of time to see significant changes especially in areas of star formation. Of course, this whole galaxy view might indeed be too broad to notice much.
But we're not really seeing a dust lane in our own galaxy on the scale that we see it in others. The visible dust lane we see splitting the Milky Way in our sky is only a very small part of the dust lane our entire galaxy likely has. It's a local, moderately small feature, and as such, we might expect it to show more change over a million years.
I tending to lean towards Ann's point of view on this one.
If the basic motion of the disk is
a constant velocity (~240 km/s) in one direction then
most stars and gas clouds should be static as seen by a gyro stabilized camera. The APOD mapping mapping shifts
almost everything in 2 million years by a mere 3º (~ 1/120 of an orbit) to the right for a camera centered upon Sagittarius A*. The Sun is situated near the inner rim of the Orion Arm and has a pretty clear dust-free shot at the Lagoon Nebula some 5,000 light years away. That nebula and the dust clouds around and behind it should do little more than simply shift ~3º to the right.
Noticeable dust lanes
in our own Orion Arm affecting the Orion Nebula, the North American Nebula, the Pelican Nebula, etc. are just 1,500 light years away and random ~20 km/s motions might well be noticed in these features over 2 million years. However, it is very unlikely that the dust would be moving that fast vs-a-vis their bright gaseous components.
[quote="Chris Peterson"][quote="geckzilla"][quote="Ann"]
As for Milky Way's dust lane, it will certainly be mostly unchanged a million years from now. The Milky Way has a thick dust lane, and a million years is almost nothing in the life of a galaxy - at least if the galaxy in question isn't undergoing a major merger in that time. And ours won't, not in just a million years![/quote]
I'm not sure we know enough to say that for certain. Dust is just as dynamic as stars and some parts change a lot while other parts aren't undergoing much change. A million years might be plenty of time to see significant changes especially in areas of star formation. Of course, this whole galaxy view might indeed be too broad to notice much.[/quote]
But we're not really seeing a dust lane in our own galaxy on the scale that we see it in others. The visible dust lane we see splitting the Milky Way in our sky is only a very small part of the dust lane our entire galaxy likely has. It's a local, moderately small feature, and as such, we might expect it to show more change over a million years.[/quote]
I tending to lean towards Ann's point of view on this one.
If the basic motion of the disk is [b][u]a constant velocity (~240 km/s) in one direction[/u][/b] then [b][u][color=#0000FF]most[/color] stars and gas clouds should be static[/u][/b] as seen by a gyro stabilized camera. The APOD mapping mapping shifts [b][u]almost everything in 2 million years by a mere 3º (~ 1/120 of an orbit)[/u][/b] to the right for a camera centered upon Sagittarius A*. The Sun is situated near the inner rim of the Orion Arm and has a pretty clear dust-free shot at the Lagoon Nebula some 5,000 light years away. That nebula and the dust clouds around and behind it should do little more than simply shift ~3º to the right.
Noticeable dust lanes [b][u]in our own Orion Arm[/u][/b] affecting the Orion Nebula, the North American Nebula, the Pelican Nebula, etc. are just 1,500 light years away and random ~20 km/s motions might well be noticed in these features over 2 million years. However, it is very unlikely that the dust would be moving that fast vs-a-vis their bright gaseous components.