🌍 How are galaxies organized in our Universe? Are they structured and ordered, or are they randomly distributed? What laws govern the organization of galaxies? Many scientists, astronomers and astrophysicists have tried to answer these questions. In 2023, we have even more technical means to study the Universe, and all its mysteries no longer seem as unattainable as before...
We now know that the Universe is made up of billions of stars, planets, comets, asteroids... And that all these celestial objects are indeed structured! First, stars are organized into galaxies. The Universe as we know it today has between 100 and 200 billion galaxies! Our own galaxy, the Milky Way, has 100 billion stars and extends over an area of around 100,000 light-years.
The galaxies themselves then organize themselves into galaxy clusters. These are galaxies bound together by the force of gravity. Clusters of galaxies extend over some ten million light-years, and there are an estimated 25 billion of them in the entire Universe!
Clusters of galaxies then organize themselves into superclusters, structures 150 million light-years in size, with a dozen or so galaxy clusters. There are an estimated 10 million in the visible Universe alone!
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💥 Galaxy Superclusters:
- But first, what exactly is a supercluster? We know that galaxies tend to cluster together, in groups of a few dozen galaxies, or in clusters of thousands. These groups and clusters of galaxies will themselves group together to form superclusters. Superclusters are gigantic groups of galaxies, sometimes hundreds of millions of light-years across! Each supercluster contains dozens of galaxy groups and clusters.
In the Virgo Supercluster, for example, we find the Local Group, the group of galaxies that hosts our own Milky Way, as well as galaxy clusters such as the Virgo Cluster and the Furnace Cluster.
The Virgo supercluster is the best-known supercluster, because it's the one we're in, but it's not the only one! The nearest supercluster is the Hydra-Centaur supercluster, which groups together two superclusters, the Centaur supercluster and the Hydra supercluster, separated by 150 to 200 million light years. The Shapley supercluster is another well-known supercluster, located 650 million light-years away in the Centaur Constellation.
Superclusters are of interest to astronomers because it is on their scale that we can see the expansion of the Universe. The expansion of the Universe is the phenomenon whereby the objects that make up the Universe, on a large scale, are moving away from each other. This is not, as we might think, the movement of galaxies away from each other, but a dilation of space. The expansion of the Universe is the solution found by Russian physicist and mathematician Alexander Friedmann to explain why the Universe has not yet collapsed under the effect of gravitation.
When we observe large-scale celestial objects, such as superclusters of galaxies, this expansion translates into an increase in the wavelength of the light emitted by the galaxies: this is known as the red shift. In contrast, the blue shift is the decrease in the wavelength of light emitted by galaxies. The redshift reflects the apparent distance between celestial objects, while the blueshift reflects their approach.
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🎬 Today's program:
- 00:00 - Introduction
- 03:28 - What is a supercluster?
- 07:25 - Introducing the Virgo supercluster
- 14:09 - The structure of the Virgo supercluster
- 15:39 - Galaxies in the Virgo Supercluster
- 17:00 - The Local Group
- 25:14 - The Sculptor's filament
- 31:35 - IC 342/Maffei Group
- 34:28 - M81 Group
- 37:57 - M101 Group
- 40:34 - Centaurus A Galaxy
- 44:15 - NGC 6744
- 45:35 - NGC 7582
- 48:00 - NGC 1023
- 49:57 - Virgo Cluster
- 54:49 - Virgo Group II
- 57:10 - Virgo Group III
- 58:36 - NGC 4697
- 01:01:30 - NGC 5033
- 01:04:04 - The Hound Dog Cloud
- 01:09:20 - Leo Group I
- 01:13:05 - Lion Group II
- 01:15:22 - NGC 2997
- 01:16:38 - The Sea Bream Group
- 01:17:49 - The Furnace Cluster
- 01:20:23 - Eridan Cluster
- 01:22:43 - The motion of the Virgo supercluster
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