APOD: Laniakea: Our Home Supercluster of... (2014 Sep 10)

[APOD Robot]

Laniakea: Our Home Supercluster of Galaxies

Explanation: It is not only one of the largest structures known -- it is our home. The just-identified Laniakea Supercluster of galaxies contains thousands of galaxies that includes our Milky Way Galaxy, the Local Group of galaxies, and the entire nearby Virgo Cluster of Galaxies. The colossal supercluster is shown in the above computer-generated visualization, where green areas are rich with white-dot galaxies and white lines indicate motion towards the supercluster center. An outline of Laniakea is given in orange, while the blue dot shows our location. Outside the orange line, galaxies flow into other galatic concentrations. The Laniakea Supercluster spans about 500 million light years and contains about 100,000 times the mass of our Milky Way Galaxy. The discoverers of Laniakea gave it a name that means "immense heaven" in Hawaiian.

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[bystander]

http://asterisk.apod.com/viewtopic.php?t=33819

[Nitpicker]

Is the orange boundary fixed and are the white "streamlines" fixed? By fixed I mean, from now until the heat-death of the universe, could dark energy, or some other energy, bring about a change to this supercluster, such that some matter might cross the boundary, inwards or outwards? Is that even possible to know?

(Analogous, I suppose, to an earthquake altering a catchment boundary on Earth, with the path and direction of waterways potentially affected.)

[geckzilla]

Laniakea has been greeted with skepticism by some. Its status as an existing, factual entity is possibly more tenuous than us lay people might guess.
http://www.thedailybeast.com/articles/2 ... avens.html

[Michael in Istanbul]

I just returned from a holiday by the sea and the picture reminds me of a flying seed that my daughter caught.

[BDanielMayfield]

Is the orange boundary fixed and are the white "streamlines" fixed? By fixed I mean, from now until the heat-death of the universe, could dark energy, or some other energy, bring about a change to this supercluster, such that some matter might cross the boundary, inwards or outwards? Is that even possible to know?

(Analogous, I suppose, to an earthquake altering a catchment boundary on Earth, with the path and direction of waterways potentially affected.)

There are a few places where superclusters have collided, as in the Bullet Cluster. So clusters can merge, but perhaps with this new way of defining superclusters both parts would have always been part of a single structure?

[Nitpicker]

Is the orange boundary fixed and are the white "streamlines" fixed? By fixed I mean, from now until the heat-death of the universe, could dark energy, or some other energy, bring about a change to this supercluster, such that some matter might cross the boundary, inwards or outwards? Is that even possible to know?

(Analogous, I suppose, to an earthquake altering a catchment boundary on Earth, with the path and direction of waterways potentially affected.)

There are a few places where superclusters have collided, as in the Bullet Cluster. So clusters can merge, but perhaps with this new way of defining superclusters both parts would have always been part of a single structure?

My understanding is that clusters and superclusters are different things, or at least that the former is one of the components of the latter.

[starsurfer]

Laniakea has been greeted with skepticism by some. Its status as an existing, factual entity is possibly more tenuous than us lay people might guess.
http://www.thedailybeast.com/articles/2 ... avens.html

It could be but then galaxy clusters are arranged into superclusters, it makes logical sense that the Milky Way is part of one. Maybe it is situated in a region of space between superclusters? Whatever the truth is, it is certainly thought provoking.

[smitty]

What is the significance of the red arrow associated with the blue dot which, according to the explanation, represents our location? The red arrow is not mentioned in the explanation. Thanks in advance for any help. Overall, very interesting!

[Markus Schwarz]

I don't quite understand the color code. The captions says that "green areas are rich with white-dot galaxies". There are no white dots at about 9 o' clock, which implies to me that the cyan represents "empty". What does, then, the dark blue next to the image center stand for? But then there are several white dots near the lower left corner, where the image is again colored cyan

[Boomer12k]

Hmmmmm.....maybe that first episodes of Star Trek:The Next Generation wasn't too far from the truth...because it looks like a JELLYFISH TO ME....

Interesting depiction...

Wikipedia search....Local Group...there is an interesting insert near bottom of page,....a section of Diagrams...that scrolls...starts from Earth...and goes out to "observable universe". Including Clusters and Super Clusters....

:---[===] *

[Indigo_Sunrise]

I don't quite understand the color code. The captions says that "green areas are rich with white-dot galaxies". There are no white dots at about 9 o' clock, which implies to me that the cyan represents "empty". What does, then, the dark blue next to the image center stand for? But then there are several white dots near the lower left corner, where the image is again colored cyan

From here:
The colors represent density within this slice, with red for high densities and blue for voids -- areas with relatively little matter. Individual galaxies are shown as white dots. Velocity flow streams within the region gravitationally dominated by Laniakea are shown in white, while dark blue flow lines are away from the Laniakea local basin of attraction. The orange contour encloses the outer limits of these streams, a diameter of about 160 Mpc.


That link doesn't specifically state what the purpose of the red arrow is, but it may be explained in another link.


Very interesting image.

[Guest]

I wonder why this specific plane was chosen for the image. I know that a single one must be, but is there some significance? Perhaps to demonstrate evidence in support of some postulate? In any case, It would be interesting to explore the data in a 4 dimensional model. The three dimensions of space (x,y,z) that could be rotated and viewed from any angle/position desired, with variable planar thickness thru the center of mass; and advanced/retarded through the (forth) time dimension. It would be interesting also to see where we came from, where we are going, and mostly to see if this super-cluster is a temporary structure destined to self destruct thru gravitational acceleration of component galaxies being flung far and wide, or if there is a semi-big crunch coming in our cosmic future. The best part is that we are going to have a front row seat for the whole event... Have to remember to get popcorn to watch the show...

[TwoElkers]

I am confused ... "everyone" tells me that the universe is expanding (Einstein, Hubble, etc.) ... yet this "contraction" of the Supercluster seems to refute that ... and if all the other galaxies outside the orange line are "contracting" toward their own supercluster centers, in my mind it follows that the Superclusters are probably also "contracting" ????????

[Markus Schwarz]

I am confused ... "everyone" tells me that the universe is expanding (Einstein, Hubble, etc.) ... yet this "contraction" of the Supercluster seems to refute that ... and if all the other galaxies outside the orange line are "contracting" toward their own supercluster centers, in my mind it follows that the Superclusters are probably also "contracting" ????????

It is a question of scale. Gravity is described by general relativity. On "small" scales gravity is very well described by Newtonian gravity. Objects attract each other and can form bound states, such as the solar system (size~30AU~0.1mpc), the Milky Way (size~32kpc), or super clusters of galaxies (size~100Mpc). However, at distances exceeding about 400Mpc Newtonian gravity is no longer valid, and the full form of general relativity (Einstein's theory of gravity) must be considered. At these large cosmological distances, the distance between the super clusters is indeed expanding.

[BDanielMayfield]

Is the orange boundary fixed and are the white "streamlines" fixed? By fixed I mean, from now until the heat-death of the universe, could dark energy, or some other energy, bring about a change to this supercluster, such that some matter might cross the boundary, inwards or outwards? Is that even possible to know?

(Analogous, I suppose, to an earthquake altering a catchment boundary on Earth, with the path and direction of waterways potentially affected.)

There are a few places where superclusters have collided, as in the Bullet Cluster. So clusters can merge, but perhaps with this new way of defining superclusters both parts would have always been part of a single structure?

My understanding is that clusters and superclusters are different things, or at least that the former is one of the components of the latter.

A retraction is in order, as I've now looked up info on both the bullet cluster and another collision site known as Abbel 520. Neither of these sites are large enough to be called superclusters.

[epitalon]

What strikes me is the fact that many streams of white dots seem to converge to our galaxy and nobody seems to care of that ???
Would our galaxy be at the center of the Universe ?

Also, please, I would like to know if we see just a cutting plane or a projection on a plane ?

[Markus Schwarz]

Also, please, I would like to know if we see just a cutting plane or a projection on a plane ?

From this link (also given in the APOD caption and mentioned by Indigo_Sunrise), I think that it's the equatorial plane. They define this plane as an imaginary plane containing many of the most massive clusters in this structure. My guess is that the white dots are galaxies (roughly) in this plane, while the color encodes the projection of the 3D galaxy density onto the equatorial plane.

[Ann]

Very interesting indeed!

Whimsically, I think Laniakea resembles a heart, but that's probably just me...

I think the definition of the boundaries of superclusters like Laniakea is very interesting, but it is not the last word on what a supercluster is.

http://www.nature.com/news/earth-s-new- ... S-20140909 wrote:

However, this work is unlikely to be the final word on what a supercluster is, says Gayoung Chon, an astronomer at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. Her team works on a different definition, based on superclusters being structures that will one day collapse into a single object. This will not happen to Laniakea, she estimates, because some of the galaxies within it will recede from one another forever.

It was Margarita who first pointed this out here. Thanks, Margarita!

Ann

[Buddy]

What is the significance of the red arrow associated with the blue dot which, according to the explanation, represents our location? The red arrow is not mentioned in the explanation. Thanks in advance for any help. Overall, very interesting!

Based on the video at the bottom of this page https://public.nrao.edu/news/pressrelea ... luster-gbt, I would say it's an axis. It's very interesting looking at the 4-D structure.

[gmPhil]

My interpretation is that blue dot is just to help locate the red arrow which points at the location of our galaxy - except that there seems to be nothing there where it's pointing! Perhaps our galaxy is too small to show, or else it's just not positioned very accurately? Whatever, it would be nice if someone who knows could throw some light on this...

[DMcCartney]

Are anyone else's suspicions roused by what appear to be radiants formed of galaxy points, both inside and outside the boundary, that seem to originate from our galaxy? Is this maybe an indication of a perspective error?

[Evenstar]

I often feel like I miss seeing the obvious when posting so here goes again. What does the little red arrow represent--its direction and location? There is no 'north' or 'up' or 'down'. Was there any reason orienting the 'picture' this way?

According to the explanation our Milky Way galaxy would be yet another white dot located in the center of the large blue dot (sphere). In fact there are probably a good number of other galaxies inside the blue dot (sphere). There is no explanation given or mention of the red arrow.

[alter-ego]

As stated in the paper's figure caption:
- The red arrow designates positive (increasing) velocities in the X axis of equatorial plane
- The orthogonal green arrow (yes there is on connected to the blue dot) designates positive (increasing) velocities in the Y axis of the equatorial plane.
- The blue dot is the Milky Way. It's size means nothing. It is a visual aid to easily show our galaxy.

Also:
- The figure shows the Supergalactic Equatorial Plane. It is the local cosmological reference plane with passes through the Sun, the Milky Way's center, and the center of the Virgo cluster of galaxies (I assume it's close the center of mass of the cluster)

[BDanielMayfield]

My interpretation is that blue dot is just to help locate the red arrow which points at the location of our galaxy - except that there seems to be nothing there where it's pointing! Perhaps our galaxy is too small to show, or else it's just not positioned very accurately? Whatever, it would be nice if someone who knows could throw some light on this...

What is the significance of the red arrow associated with the blue dot which, according to the explanation, represents our location? The red arrow is not mentioned in the explanation. Thanks in advance for any help. Overall, very interesting!

Based on the video at the bottom of this page https://public.nrao.edu/news/pressrelea ... luster-gbt, I would say it's an axis. It's very interesting looking at the 4-D structure.

There are actually three arrows, red, blue and green, and they each point away from our galaxy along the x, y, and z coordinate planes. When the simulation shows a blue dot (or a red or green one too) the view is straight along one of the planes toward us (the Milky Way, that is).