4
$\begingroup$

I sincerely apologize if this question is stupid, however after all the articles I read so far, I could not confirm this assumption, which I think is actually a fact, but I'm not completely confident.

I'm writing on the topic of proportions of the universe, and in one of the statements I claim the following:

"Just one small void inside a supercluster of galaxies can span across 10 to 20 megaparsecs (32 to 65 million light-years ) in diameter."

Let me state that I understand that a void within a galaxy supercluster may not necessarily be completely surrounded by galaxies of that supercluster, and can extend far out from the supercluster it partially occupies, so to clarify what I mean by my question on a practical example:

If you were to draw a straight line across a map of a galaxy supercluster, can that line start inside a group of galaxies of that supercluster, go across a void of 10 - 20 megaparsecs, and end inside another group of galaxies of that same supercluster?

(I am basing my "small" classification of a cosmic void 10 - 20 megaparsecs in diameter on the Wikipedia article "Void (Astronomy)" https://en.wikipedia.org/wiki/Void_(astronomy) in which it says:

" ...Voids typically have a diameter of 10 to 100 megaparsecs; particularly large voids, defined by the absence of rich superclusters, are sometimes called supervoids. ..."

My only goal is basically to find out whether I would be wrong or not if I state that small voids of 10 - 20 megaparsecs, really actually exist within, and not only between superclusters.

For any eventual help on this topic, I would be sincerely grateful.

Kind regards

$\endgroup$
2
$\begingroup$

My only goal is basically to find out whether I would be wrong or not if I state that small voids of 10 - 20 megaparsecs, really actually exist within, and not only between superclusters.

The largest structure is called a filament.

We are in the supercluster Laniakea, in the smaller supercluster Virgo, in the Milky Way galaxy, in the Solar system, on Earth.

It looks like this:

Earth to Laniakea$$\text{Click to zoom in - 23,624 × 2,953 pixels}$$ Laniakea$$\text{Laniakea}$$

Here we are:

Our Local Group

Wikipedia says:

Distribution: cosmic voids and sheets

Research has tried to understand the way superclusters are arranged in space. Maps are used to display the positions of 1.6 million galaxies. Three-dimensional maps are used to further understand the positions of these superclusters. To map them three-dimensionally, the position of the galaxy in the sky as well as the galaxy's redshift are used for calculation. The galaxy's redshift is used with Hubble's law to determine its position in three-dimensional space.

It was discovered from those maps that superclusters of galaxies are not spread uniformly across the universe but they seem to lie along filaments. Maps reveal huge voids where there are extremely few galaxies. Some dim galaxies or hydrogen clouds can be found in some voids, but most galaxies are found in sheets between the voids. The voids themselves are often spherical but the superclusters are not. They can range from being 100 million to 400 million light-years [that's 30.660139381 to 122.64055752 megaparsec] in diameter. The pattern of sheets and voids contains information about how galaxy clusters formed in the early universe.

There is a sponge analogy used often that compares a sponge to the pattern of clusters of galaxies in the universe – the holes are the voids and the other parts are the locations of the superclusters.".

So, yes - there are small and large voids.

See also this Wikipedia page:

Galaxy distribution

The number density of galaxies in the LS falls off with the square of the distance from its center near the Virgo Cluster, suggesting that this cluster is not randomly located. Overall, the vast majority of the luminous galaxies (less than absolute magnitude −13) are concentrated in a small number of clouds (groups of galaxy clusters). Ninety-eight percent can be found in the following 11 clouds (given in decreasing order of number of luminous galaxies): Canes Venatici, Virgo Cluster, Virgo II (southern extension), Leo II, Virgo III, Crater (NGC 3672), Leo I, Leo Minor (NGC 2841), Draco (NGC 5907), Antlia (NGC 2997) and NGC 5643. Of the luminous galaxies located in the disk, one third are in the Virgo Cluster, while the remainder are found in the Canes Venatici Cloud and Virgo II Cloud, plus the somewhat insignificant NGC 5643 Group. The luminous galaxies in the halo are also concentrated in a small number of clouds (94% in 7 clouds). This distribution indicates that "most of the volume of the supergalactic plane is a great void." A helpful analogy that matches the observed distribution is that of soap bubbles. Flattish clusters and superclusters are found at the intersection of bubbles, which are large, roughly spherical (on the order of 20–60 Mpc in diameter) voids in space. Long filamentary structures seem to predominate. An example of this is the Hydra-Centaurus Supercluster, the nearest supercluster to the LS, which starts at a distance of roughly 30 Mpc and extends to 60 Mpc.

$\endgroup$
2
  • $\begingroup$ This is great. Thank you Rob! I see that my original statement would be sort of self-serving, taking advantage of the natural structuring of filaments. Perhaps a better statement would than be: "Just one small void between two galaxy clusters belonging to the same supercluster can be (so and so) in diameter." Would you agree? Thanks again, I appreciate your explanation. Best $\endgroup$ – InAwe Jun 12 '18 at 12:50
  • $\begingroup$ Filaments, clusters, superclusters, voids are all parts of the "Cosmic Web", the largest structural entity in the Universe. The inter-relationships between these elements is beautifully described and illustrated in this golden oldie article: arxiv.org/pdf/0708.1441.pdf . Since that was written we have more data, better models and a greater understanding of cosmic structure, but its a good starting place. $\endgroup$ – JonesTheAstronomer Jun 12 '18 at 21:54

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.