APOD: Two Million Stars on the Move (2017 Apr 17)

Comments and questions about the APOD on the main view screen.
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Ann
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Re: APOD: Two Million Stars on the Move (2017 Apr 17)

Postby Ann » Mon Apr 17, 2017 10:55 pm

geckzilla wrote:
Ann wrote:Black and white is the new black for APOD!

Seriously, this kind of APOD could not have been made in color. I like the APOD. It is fascinating, and I look forward to more from Gaia!

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!

Ann

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.


What I meant was that the dust lane will not go away in a million years. I googled "edge-on galaxy" and got all sorts of galaxies with dust lanes. One galaxy that seems to lack a "regular" dust lane is M82, which is undergoing convulsions of star formation. Nothing like that is likely to happen to the Milky Way in the next million years.

So like you said, star formation is likely to cause some local changes in the central dust lane, but I think it is beyond the capabilities of Gaia to predict that.

Ann
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Chris Peterson
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Re: APOD: Two Million Stars on the Move (2017 Apr 17)

Postby Chris Peterson » Mon Apr 17, 2017 11:19 pm

Ann wrote:What I meant was that the dust lane will not go away in a million years. I googled "edge-on galaxy" and got all sorts of galaxies with dust lanes.

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.
Chris

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ENORTON II

Re: APOD: Two Million Stars on the Move (2017 Apr 17)

Postby ENORTON II » Tue Apr 18, 2017 12:40 am

It would have been nice to have the stars in the familiar constellations highlighted to see how things change. It seems random.

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wish list

Postby Luxi_Turna » Tue Apr 18, 2017 12:44 am

BDanielMayfield wrote:2. Add more contrast. The brightness range of stars vary tremendously, way more than we even can accurately depict, but this sim doesn't show bright stars at all.[/list]


Yeah. I downloaded it and watched in my media player with the contrast up. You MUST try that!

ALSO ON THE WISH LIST:
run the simulation longer. I want to watch the galaxy rotate. On the other hand, the naked eye stars are all in the Perseus arm (I think), which probably moves as a unit. But I'd like to see stars oscillate above and beneath the galactic plane.

ALSO: an option (or a new vid) that only shows the stars that move, not the unchanging background.

ALSO:
a version with vector arrows reaching out from each star.

AND: a much faster version. Even 2x looks sluggish. I want to see what the galaxy is doing.

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Re: Gaia: Two Million Stars on the Move

Postby Luxi_Turna » Tue Apr 18, 2017 1:22 am

I usually think APOD pix are real cool! But this one was scary, kind of. Everything about the galaxy is, because it's so big.

A galactic year is a quarter-billion years. That means it rotates one milliarcsec every 70 days. In my whole life it will only rotate 400 milliarcsecs. That's less angle than a meter-wide telescope can resolve, and it's my whole life.

...okay, it's stupid. But the galaxy is still scary to me anyway. Thinking about it makes me not want to be alone.

PS: Great video, BTW! Amazing. It needs more contrast though, and the simulation should run faster and for more years in the same 50-second video. I mean, IMHO. ☺ Most of the stars that move, you can barely see them move at all.

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Re: APOD: Two Million Stars on the Move (2017 Apr 17)

Postby Luxi_Turna » Tue Apr 18, 2017 1:25 am

ENORTON II wrote:It would have been nice to have the stars in the familiar constellations highlighted .


No it wouldn't. I hate looking at star-field pix through the visual noise of make-believe animals and star name text. None of that is real. But hey, that's just me.

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Re: APOD: Two Million Stars on the Move (2017 Apr 17)

Postby Luxi_Turna » Tue Apr 18, 2017 1:32 am

Ann wrote:star formation is likely to cause some local changes in the central dust lane

Mmm, I don't know about that, Ann. Sure, you're more likely to see a new one in a dust lane, but a million years is just an eyeblink. A star's life is ten thousand times longer than that.

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Re: wish list

Postby bystander » Tue Apr 18, 2017 3:29 am

Luxi_Turna wrote:
ALSO ON THE WISH LIST:[/b] run the simulation longer. I want to watch the galaxy rotate. On the other hand, the naked eye stars are all in the Perseus arm (I think), which probably moves as a unit. But I'd like to see stars oscillate above and beneath the galactic plane...

ESA's video runs 5 million years
Click to play embedded YouTube video.
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Re: APOD: Two Million Stars on the Move (2017 Apr 17)

Postby 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.
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Re: APOD: Two Million Stars on the Move (2017 Apr 17)

Postby Chris Peterson » Tue Apr 18, 2017 4:35 am

neufer wrote:
Chris Peterson wrote:
geckzilla wrote: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.

Don't misunderstand me... I also think the same. I was just pointing out that the dust lane we see in the Milky Way is quite different from the dust lanes we see in other galaxies.
Chris

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Ann
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Re: APOD: Two Million Stars on the Move (2017 Apr 17)

Postby Ann » Tue Apr 18, 2017 2:19 pm

Click to play embedded YouTube video.
Well, I agree with Geck that some high-mass star formation may affect the dust lane in places. But it is hard to predict exactly how the dust lane will evolve, even though GLIMPSE/MIPSGAL has given us a good idea where of to find future high-mass star formation.

Ann
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