Before your eyes is a computer model that shows a supercluster of galaxies called Laniakea, and our place in it. The red dot in the image is not the Earth or even the Solar System, but our Milky Way.
Scientists have long tried to understand where exactly our Galaxy is located in the Universe. In 2014, a team of researchers collected data on nearly 100,000 galaxies and mapped their locations and movements through space. For the first time, we saw that the Milky Way is part of a much larger system of galaxies – a supercluster that scientists called Laniakea.
The approximate diameter of this supercluster is 520 million light years, and the Milky Way is located far from its center, almost on the very outskirts.
In Laniakea, on the opposite side of the Milky Way, there is a gravitational anomaly – the so-called Great Attractor, to which, as it turned out, most of the supercluster galaxies migrate (including us).
By the way, the diameter of the Milky Way is about 200,000 light years, this was concluded by researchers from the Canary Institute of Astrophysics as part of the Apogee and Lamost missions. And there are from 200 to 400 billion stars in our Galaxy.
The Beast
Most people are not informed about the Great Attractor’s existence, at least beyond the resounding name. Attention should be paid to the title “Great”. If in a universe, the grandeur of even the observable part of which goes beyond the imagination, something is called “great”, it is for a reason.
The Great Attractor is a gravitational anomaly, a violation of the uniformity of matter density in the universe, a quarter of a billion light years away from us. The mass of the anomaly reaches 100 thousand masses of the Milky Way which is 10% of the mass of the Laniakea hypercluster, a grandiose lens with a diameter of 500 million light years. The hypercluster consists of about 100 superclusters, one of which is ours – the “Local Group” of about a hundred galaxy clusters, one of which belongs to the Milky Way.
And all this, like tea leaves in a mug, revolves around the Great Attractor, located in the center of Laniakea. Here you may be surprised at the numbers – but this is just a dry number of zeros. It’s worth starting with how the Great Attractor was found. It was possible to see the consistent motion of about a million galaxies around a common center of mass thanks to measurements of velocities relative to the cosmic microwave background radiation.
For the case of the Milky Way, the “extra” speed, which cannot be explained by rotation around the centers of mass of the cluster and the Local Group, reaches 600 kilometers per second. When determining the motion vectors of many other galaxies, also “filtered” from local gravitational movements, it was made possible to construct a three-dimensional picture and calculate the mass of the Attractor.
That’s how it was found
First, at the tip of the pen, because the point at which the gravitational anomaly is located turned out to be hidden from observation of dust accumulations in the galactic disk. Only radio and X-ray telescopes were able to break through this veil.
What turned out to be the Great Attractor? Technically, nothing special. At least, as far as we were able to see, the anomaly is simply a very large and dense supercluster – ten times the norm. But here we need to remember what a “supercluster” is called.
A supercluster is the “primary pancake” – the first generation of inhomogeneities – disk-shaped clouds of hydrogen into which a continuous mass of gas broke up shortly after the recombination epoch – 380 thousand years after the Big Bang. A supercluster with a mass of about 1000 masses of giant galaxies is an extremely large heterogeneity of mass distribution.
However, even in the young universe, several clouds merged, forming an anomaly and spinning dozens of other “pancakes” around themselves. This is how Attractor and Laniakea arose and then fell apart.
At the moment, Laniakea is torn apart by the expansion of space and is flying apart. The Milky Way falls onto the Attractor at a speed of 600 km/s, but the Attractor moves away at a speed of 5000 km/s. Gravitational connectivity is broken not only in hyperclusters, but also in ordinary superclusters. In particular, Local Group clusters fly away at speeds higher than their gravitational motion. The tangential velocities of galaxies in hyper- and superclusters are preserved only because there is no resistance from the medium. The local supercluster fell off like a stone from a sling and is now moving away from the Attractor.
But at the same time, in the Attractor itself, the gravitational connectivity of 10 thousand (100 thousand, counting dwarfs) galaxies can currently be preserved. This is a region with a very high density of galactic population and the probable birthplace of supergiant galaxies – obtained by the merger of ten or even a hundred star clouds the size of the Milky Way.
In practice, however, this only means that a hypothetical Dark Lord on a cosmic scale – such people usually want to conquer the entire galaxy – will encounter difficulties in the Attractor. He will need much more time and Death Stars, plus other galaxies are so close that they are tempting.
And by the way, if there are too many galaxies in the Attractor, then where did they come from? The compaction occurred due to the growth of voids – voids between the “pancakes”. The colossal void – the Repulsor (for galaxies fly from it) – was found 800 million light years from the Solar System.
