Image 1 Caption: A map of the large-scale structure of the universe of the local universe out to ∼ 150 Mpc = 0.15 Gpc (∼ 1 % of the observable universe radius = 14.3 Gpc) from the center at the unlabeled Milky Way: i.e., to cosmological redshift z ≅ 0.035 and lookback time ≅ 0.5 Gyr.

Features:

1. Recall the observable universe radius = 14.3 Gpc is a model-dependent result since it is the radius at the present instant in cosmic time which is equal to the age of the observable universe = 13.797(23) Gyr (Planck 2018) which is also a model-dependent result.

   The model used is Λ-CDM model which has been the standard model of cosmology (SMC, Λ-CDM model) since circa 1998. However, it may need revision or replacement. See /big_bang_cosmology_limitations.html.

2. To convert cosmological physical distance (i.e., cosmological proper distance) to cosmological redshift, we uses the 1st order-in-z Hubble's law zc = H_0*d with vacuum light speed c = 2.99792458*10**5 km/s, H_0 = 70 (km/s)/Mpc (a fiducial value probably correct to within 5 percent), and d = 150 Mpc.

3. One can see galaxy superclusters, galaxy filaments, galaxy walls, and voids.

   The web-like nature of the large-scale structure of the universe is somewhat apparent---hence the modern name for the large-scale structure the cosmic web.

   Yours truly thinks it's more like "cosmic foam".

4. The Milky Way (NOT labeled) is at the center of the map, it is in the Local Group of galaxies (NOT labeled) which is in the Virgo Supercluster which is now recognized as part of a larger galaxy supercluster called the Laniakea Supercluster.

5. Features of galaxy superclusters:

   1. Conventionally, galaxy superclusters are only vaguely defined: "extended regions containing a large number of galaxies" (Tempel 2014). Yours truly believes that galaxy superclusters are usually just defined by eye: e.g., "hey, that combination galaxy groups and clusters looks like a connected structure: let's call it a galaxy supercluster."

   2. They have a scale of order 100 Mpc to 3 Gpc (see Wikipedia: Supercluster: Existence). The largest ones are larger than the 370 Mpc limit for extent of largest large scale structure by a modern determination of the validity of the cosmological principle: i.e., the assumption/observation that observable universe is homogeneous (i.e., same in all places) and isotropic (i.e., same in all directons) on a large enough scale. However, the largest galaxy superclusters are arguably just large fluctuations from average behavior (see observable_universe_cosmological_principle.html).

   3. They make up ∼ 5 % by volume??? of the observable universe (see Wikipedia: Supercluster: Existence) which is estimated to contain ∼ 10 million of them (see Wikipedia: Supercluster).

   4. They can often be considered as made of galaxy filaments and galaxy walls (see Wikipedia: Supercluster: Existence).

   5. About 85 % of their mass is dark matter Only ∼ 15 % of the mass is baryonic matter and only ∼ 1.5 % is in stars: most of the baryonic matter is intergalactic medium which has very low density, but occupies a lot of volume. The intergalactic medium is probably just has the primordial cosmic composition Recall primordial cosmic composition consists of just hydrogen (∼ 0.75 mass fraction), deuterons (∼ 10**(-3) mass fraction), helium (∼ 0.25 mass fraction), and a little lithium (Li) (∼ 10**(-9) mass fraction).

   

6. Image 2 Caption: A map of the large-scale structure of the universe of the local universe out to ∼ 300 Mpc = 0.30 Gpc (∼ 2 % of the observable universe radius = 14.3 Gpc) from the center at the unlabeled Milky Way: i.e., to cosmological redshift z ≅ 0.07 and lookback time ≅ 1 Gyr.

7. The Laniakea Supercluster is marked in yellow in Image 2.

   Features of the Laniakea Supercluster:

   1. The Laniakea Supercluster contains the Virgo Supercluster, the Great Attractor (NOT labeled), Hydra-Centaurus Supercluster, Pavo-Indus Supercluster, the Southern Supercluster (NOT labeled) which includes the Fornax Cluster (see Wikipedia: Laniakea Supercluster: Characteristics).

   2. Laniakea's longest axis is ∼ 160 Mpc and its gravitational center point is the Great Attractor (∼ 80 Mpc away) which is located in constellation Norma in the southern hemisphere of the celestial sphere (see Wikipedia: Laniakea Supercluster: Characteristics). It's a little hard to tell where the Great Attractor is in Image 1 or Image 2, but probably somewhere between the Hydra-Centaurus Supercluster and the Pavo-Indus Supercluster.

   3. Laniakea contains ∼ 10**5 galaxies (NOT counting endless dwarf galaxies???) and has total mass ∼ 10**17 M_☉ (counting dark matter).

   4. Unlike other superclusters, Laniakea is defined by a definite objective specification.

      Superimposed on the recession velocities of galaxies due to the expansion of the universe are peculiar velocities.

      One can define a closed surface in space, where the peculiar velocities go to zero. Going outward from the closed surface the peculiar velocities point outward; going inward, they point inward.

      The closed surface is analogous to the watershed for internal drainage basin.

      Laniakea is defined by a closed surface such as which we have just specified (see, e.g., Tempel 2014). Alas, applying the specification of the closed surface requires vast amounts of accurate/precise data which so far is only available for Laniakea itself. In fact, there may NEVER be another Laniakea-like-defined supercluster or at least none so accurately defined as Laniakea itself. There also may NOT be so much importance in defining superclusters the rule used for Laniakea.

8. The scales of the sphere regions of the observable universe shown in Image 1 (diameter ≅ 300 Mpc) and Image 2 (diameter ≅ 600 Mpc) are probably large enough that the contents have about average behavior as the observable universe as whole at this instant in cosmic time which is equal to the age of the observable universe = 13.797(23) Gyr (Planck 2018) according to the Λ-CDM model) as aforesaid.

   In other words, sphere have reached or nearly reached the size scale 370 Mpc (see observable_universe_cosmological_principle.html). where the cosmological principle applies: i.e., observable universe is homogeneous (i.e., same in all places) and isotropic (i.e., same in all directons) on a large enough scale.

   There are rarely greater large-scale structures than those we see in Image 1 and Image 2. There is seems to be a limit to their size---an End of Greatness.

   Note that 370 Mpc = 0.370 Gpc is a significant fraction of the observable universe which has radius 14.3 Gpc (≅ 46.6 Gly) according to the Λ-CDM model as aforesaid (see Wikipedia: Observable universe).

9. The cosmological principle is, in fact, a basic assumption of Big Bang cosmology. So it is satisfying that it has been confirmed observationally so far (see observable_universe_cosmological_principle.html).

Images:

1. Credit/Permission: © Richard Powell 2009 (uploaded to Wikipedia by User:Zaerp, 2009) / Creative Commons CC BY-SA 2.5.
   Image link: Wikipedia: File:Nearsc.gif.
   
2. Credit/Permission: © Richard Powell 2016 (uploaded to Wikipedia by User:AdAstraPerScientiam, 2009) / Creative Commons CC BY-SA 2.5.
   Image link: Wikimedia Commons: File:Laniakea.gif.
   

Local file: local link: large_scale_structure_z_0x035.html.
File: Cosmology file: large_scale_structure_z_0x035.html.