APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Comments and questions about the APOD on the main view screen.

APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby APOD Robot » Tue Jul 17, 2012 4:06 am

Image Simulation: A Disk Galaxy Forms

Explanation: How do galaxies like our Milky Way form? Since our universe moves too slowly to watch, faster-moving computer simulations are created to help find out. Green depicts (mostly) hydrogen gas in the above movie, while time is shown in billions of years since the Big Bang on the lower right. Pervasive dark matter is present but not shown. As the simulation begins, ambient gas falls into and accumulates in regions of relatively high gravity. Soon numerous proto-galaxies form, spin, and begin to merge. After about four billion years, a well-defined center materializes that dominates a region about 100,000 light-years across and starts looking like a modern disk galaxy. After a few billion more years, however, this early galaxy collides with another, all while streams of gas from other mergers rain down on this strange and fascinating cosmic dance. As the simulation reaches half the current age of the universe, a single larger disk develops. Even so, gas blobs -- some representing small satellite galaxies -- fall into and become absorbed by the rotating galaxy as the present epoch is reached and the movie ends. For our Milky Way Galaxy, however, big mergers may not be over -- recent evidence indicates that our large spiral disk Galaxy will collide and coalesce with the slightly larger Andromeda spiral disk galaxy in the next few billion years.

<< Previous APOD This Day in APOD Next APOD >>
User avatar
APOD Robot
Otto Posterman
 
Posts: 1845
Joined: Fri Dec 04, 2009 3:27 am

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby Beyond » Tue Jul 17, 2012 4:19 am

Aw man.... i wish he coulda gone a few more billion years with it. I was really enjoying it, then it stopped. Bummer! Kinda reminds me of Disco.
Do a little dance, spin a lotta dust, become alive-become alive.
To find the Truth, you must go Beyond.
User avatar
Beyond
500 Gigaderps
 
Posts: 6496
Joined: Tue Aug 04, 2009 11:09 am
Location: BEYONDER LAND

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby Case » Tue Jul 17, 2012 4:45 am

APOD wrote:Pervasive dark matter is present but not shown.

Yet, in this simulation, the center rotates much faster than the outer regions :?: , even at t=13.6.
User avatar
Case
Science Officer
 
Posts: 432
Joined: Sat Jun 09, 2007 10:08 pm
Location: (52°N, 06°E)

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby neufer » Tue Jul 17, 2012 5:28 am

Case wrote:
APOD wrote:
Pervasive dark matter is present but not shown.

Yet, in this simulation, the center rotates much faster than the outer regions :?: , even at t=13.6.

Velocities should be roughly constant regardless of distance from the center.
Art Neuendorffer
User avatar
neufer
Vacationer at Tralfamadore
 
Posts: 11631
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby Vincent Pinto » Tue Jul 17, 2012 9:09 am

while time is shown in billions of years since


None of us who read this or those who posted the original quote were there then to so professorially say it took that much time. More importantly, the assumptions used to make the statement in the quote are non-verifiable assumptions, and therefore to posit the notion it took that long is certainly not science. It would however most emphatically constitute a belief. Since the same vein, there are some people, I'm told, who believe in a flat earth.
Vincent Pinto
Asternaut
 
Posts: 4
Joined: Mon Apr 02, 2012 6:02 am
Location: Bangalore, India

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby Guest » Tue Jul 17, 2012 9:11 am

This video was a good example of an optical illusion. The clouds seem to keep moving well after the movie stopped.
Guest
 

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby ThePiper » Tue Jul 17, 2012 9:55 am

neufer wrote:Velocities should be roughly constant regardless of distance from the center.


@neufer
Are you sure? In this case we would have a homogenous disk. But We have spirals because of the speed-gradients between the center and the outer areas.
§ The Idiot Outside of Intels Inside
User avatar
ThePiper
Ensign
 
Posts: 35
Joined: Wed Mar 16, 2011 10:16 am
Location: Switzerland

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby Boomer12k » Tue Jul 17, 2012 10:12 am

One...reminds me of how cotton candy is formed. Forming around the central slim cone.

Two...Dark Matter is supposed to be what makes a galaxy appear to rotate as a single unit..as the Gravity is supposed to be very much beyond the mere edge of a galaxy, and caused by 90% dark matter, (that you cannot detect, so far)...as discovered by Carolyn Shoemaker, (she was examining the spectroscopy of galaxies)...I have observed that this is basically an illusion as our own galaxy has stars of various speeds, both apparently approaching and receding from us, so not all are swirling in the same manner. Also we bob up and down in the galaxy, (gravity wave?), as on Dec. 21st, 2012 we are going to cross the galactic equator. Hope to see you all the next day. :wink:

Three...The simulation does not run out of material...more and more material seems to just generate and fall into the galaxy, was Fred Hoyle correct? --- I am assuming that the simulation is much larger than just this one area. (As I see other material go by)...But in the real universe, in our own galactic area, while we do have smaller satellite galaxies and such, I don't see them coming in and joining like cotton candy, at the edges like it appears to be here...our galaxy seems more...constant....I think is the word I am looking for...we don't see "extra galactic material" falling into M31, from the sides, for instance...maybe it just represents dust and gas, and not star formation...lot of things the article does not explain, but hey, pressed for space, I guess.

Four...Galaxy formation here seems to be VERY clumpy. I realize this is only one type of galaxy, very much like M63. But there are VERY SMOOTH galaxies like M104.

Still, interesting and thought provoking.

:---[===] *
Boomer12k
:---[===] *
 
Posts: 1100
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby winstond » Tue Jul 17, 2012 11:14 am

Why does it start to spin and what keeps it spinning?
winstond
 

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby neufer » Tue Jul 17, 2012 12:39 pm

Rotation curve of a typical spiral galaxy: predicted (A) and observed (B).
The discrepancy between the curves can be accounted for
by adding a dark matter component to the galaxy.
ThePiper wrote:
neufer wrote:
Velocities should be roughly constant regardless of distance from the center.

Are you sure? In this case we would have a homogenous disk.
But We have spirals because of the speed-gradients between the center and the outer areas.

We have spirals due to some sort of
dynamic (quasi-)standing gravitational wave.
Art Neuendorffer
User avatar
neufer
Vacationer at Tralfamadore
 
Posts: 11631
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby Tszabeau » Tue Jul 17, 2012 12:41 pm

I'll never again look at dust bunnies the same.
Tszabeau
 

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby neufer » Tue Jul 17, 2012 12:46 pm

Click to play embedded YouTube video.


winstond wrote:
Why does it start to spin and what keeps it spinning?


Art Neuendorffer
User avatar
neufer
Vacationer at Tralfamadore
 
Posts: 11631
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Simulation: A Galaxy Forms (2012 Jul 17)

Postby Virgin Islands » Tue Jul 17, 2012 12:55 pm

Better keep this simulation away from that vacuum cleaner fella - Dyson or we will be watching it in his commercials.
Virgin Islands
 

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby neufer » Tue Jul 17, 2012 1:06 pm

Vincent Pinto wrote:
while time is shown in billions of years since

None of us who read this or those who posted the original quote were there then to so professorially say it took that much time.

    Orin possibly :?:
Vincent Pinto wrote:
More importantly, the assumptions used to make the statement in the quote are non-verifiable assumptions, and therefore to posit the notion it took that long is certainly not science. It would however most emphatically constitute a belief. Since the same vein, there are some people, I'm told, who believe in a flat earth.

In point of fact, the only galaxies that we are able to observe are from the past...mostly from billions of years in the past:
http://supercom.org/oldest-known-galaxy ... ed/433195/ wrote:
<<Astronomers using the Hubble Space Telescope have discovered what scientists think is the oldest galaxy so far detected, a galaxy so far away that the light from it has taken 13.2 billion light years to reach us, here on earth. It is so old that it is thought to be one of the earliest galaxies ever formed, just 480 million years after the Big Bang.

Scientists believe that galaxies started to form 200 to 300 million years after the Big Bang as new stars clustered together, then evolved into baby galaxies then eventually into large galaxies that we see today.

The newly detected galaxy was discovered using Hubbles’s recently installed Wide Field Planetary Camera 3 combined with Hubble’s eight feet wide mirror. The galaxy is calculated to be small compared to our own galaxy, the milky way, at one hundredth its size.

Astronomers and scientists are looking forward to the launch of NASA’s James Webb telescope sometime after 2014. This will enable observers to look back even further in time to when the galaxies were just forming.>>
Art Neuendorffer
User avatar
neufer
Vacationer at Tralfamadore
 
Posts: 11631
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby eltodesukane » Tue Jul 17, 2012 1:16 pm

ThePiper wrote:
neufer wrote:Velocities should be roughly constant regardless of distance from the center.


@neufer
Are you sure? In this case we would have a homogenous disk. But We have spirals because of the speed-gradients between the center and the outer areas.


constant velocities still implies non-constant angular velocities, so there is no contradiction
eltodesukane
Ensign
 
Posts: 48
Joined: Sun Jan 01, 2012 12:40 am

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby orin stepanek » Tue Jul 17, 2012 2:14 pm

neufer wrote:Orin possibly :?:


:? Not that I remember! :wink:
Orin

Smile today; tomorrow's another day!
User avatar
orin stepanek
Plutopian
 
Posts: 4265
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby Margaretta » Tue Jul 17, 2012 2:39 pm

Fantastic simulation. Thank you. Do the particles of two merged galaxies speed up, maintain speed or slow down?
Margaretta
Asternaut
 
Posts: 1
Joined: Tue Jul 17, 2012 2:32 pm

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby ems57fcva » Tue Jul 17, 2012 3:00 pm

I'm not very impressed by this simulation. No central bulge (and at least an insignificant one), no dust lanes, and no bridges between the centers of the galaxies after a close encounter. So I see there as being a long ways to go here.
ems57fcva
Ensign
 
Posts: 36
Joined: Wed Feb 24, 2010 1:13 am
Location: Falls Church, VA

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby neufer » Tue Jul 17, 2012 3:12 pm

ems57fcva wrote:
I'm not very impressed by this simulation. No central bulge (and at least an insignificant one), no dust lanes, and no bridges between the centers of the galaxies after a close encounter. So I see there as being a long ways to go here.

No bars or spiral arms to speak of for that matter.

Personally, I think that it is really neat that there is still a long ways to go here.
Art Neuendorffer
User avatar
neufer
Vacationer at Tralfamadore
 
Posts: 11631
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby neufer » Tue Jul 17, 2012 3:16 pm

Margaretta wrote:
Do the particles of two merged galaxies speed up, maintain speed or slow down?

The kinetic energy of the individual stars can only increase
as they feed off of the potential energy of unmerged galaxies.
Art Neuendorffer
User avatar
neufer
Vacationer at Tralfamadore
 
Posts: 11631
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby FloridaMike » Tue Jul 17, 2012 3:35 pm

I have done this simulation dozens of times, with cream and a cup of coffee....
Certainty is an emotion.
FloridaMike
Science Officer
 
Posts: 216
Joined: Fri Nov 04, 2011 2:21 pm
Location: Florida, USA

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby Chris Peterson » Tue Jul 17, 2012 3:46 pm

Boomer12k wrote:Two...Dark Matter is supposed to be what makes a galaxy appear to rotate as a single unit..as the Gravity is supposed to be very much beyond the mere edge of a galaxy, and caused by 90% dark matter, (that you cannot detect, so far)...as discovered by Carolyn Shoemaker, (she was examining the spectroscopy of galaxies)...

It was Vera Rubin, not Carolyn Shoemaker, who first noted the peculiarities in galactic rotation curves that were suggestive of dark matter halos (dark matter itself had already been inferred from earlier observations of the motions of galaxies in clusters).

Also we bob up and down in the galaxy, (gravity wave?), as on Dec. 21st, 2012 we are going to cross the galactic equator.

We don't bob up and down, but rather, orbit on a plane slightly inclined to the nominal galactic plane. We won't be on the galactic equator on Dec 21, however.

Three...The simulation does not run out of material...more and more material seems to just generate and fall into the galaxy, was Fred Hoyle correct?

No, Hoyle was wrong. No new material is being created in this simulation, it's just falling in from outside the volume that is being rendered. The simulation correctly considers that the Universe is bigger than just the region visualized.

--- I am assuming that the simulation is much larger than just this one area. (As I see other material go by)...But in the real universe, in our own galactic area, while we do have smaller satellite galaxies and such, I don't see them coming in and joining like cotton candy, at the edges like it appears to be here...our galaxy seems more...constant....I think is the word I am looking for...we don't see "extra galactic material" falling into M31, from the sides, for instance...maybe it just represents dust and gas, and not star formation...lot of things the article does not explain, but hey, pressed for space, I guess.

This is a simple simulation in some respects. It's just modeling gas and allowing stars to form from the gas. I don't think the elemental evolution of the galaxy is being considered at all- there's nothing here but hydrogen and maybe helium. No dust, no metals. I'm not at all sure this doesn't reasonably simulate how our galaxy formed, as well. The small cluster we're a part of strongly suggests a period of infall very like what the simulation shows.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
User avatar
Chris Peterson
Abominable Snowman
 
Posts: 9444
Joined: Wed Jan 31, 2007 11:13 pm
Location: Colorado, USA

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby ddale51 » Tue Jul 17, 2012 8:37 pm

Wow. Fascinating stuff. It seems to me that I detect a bit of a bar that forms in the center of the later galaxy. It's not very prominent but it kind of shows how maybe the bar can form on a larger scale, something I've been puzzled about ever since I first saw the bars in photos of spiral galaxies (though I'm hardly an expert in such matters). Is this a valid observation?
ddale51
Ensign
 
Posts: 12
Joined: Thu Jan 27, 2011 6:37 pm

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby Chris Peterson » Tue Jul 17, 2012 8:49 pm

ddale51 wrote:Wow. Fascinating stuff. It seems to me that I detect a bit of a bar that forms in the center of the later galaxy. It's not very prominent but it kind of shows how maybe the bar can form on a larger scale, something I've been puzzled about ever since I first saw the bars in photos of spiral galaxies (though I'm hardly an expert in such matters). Is this a valid observation?

I agree. We're seeing a barred spiral galaxy form.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
User avatar
Chris Peterson
Abominable Snowman
 
Posts: 9444
Joined: Wed Jan 31, 2007 11:13 pm
Location: Colorado, USA

Re: APOD: Simulation: A Disk Galaxy Forms (2012 Jul 17)

Postby richiem » Wed Jul 18, 2012 1:45 am

Sim doesn't run for me -- and they always have before. Is there something different about this one?
richiem
 

Next

Return to The Bridge: Discuss an Astronomy Picture of the Day

Who is online

Users browsing this forum: Baidu [Spider], Bing [Bot], Boomer12k, ta152h0 and 6 guests