Planet Earth may seem immense before our eyes, you just have to think that to cross the Atlantic it takes at least ten hours of our lives. A trip around the world can take whole months with decent stopovers. However, from a cosmic perspective our planet seems to be anything but special, especially if you think about Laniakea, the supercluster that houses us, which by the way, is being destroyed by dark energyright in front of our eyes.
What is Laniakea?
Let’s get a little into cosmic geography. Our planet revolves around the Sun, which is located right in the center of the Solar System, located in the Orion arm of a spiral galaxy called Milky Way about 100 thousand light years in diameter. In turn, the Milky Way forms part of what astrophysicists call ‘Local group‘, which is a group of about 25 galaxies and whose diameter is about 10 million light years.
But not here for the fractal beauty of the Universe, in turn our ‘Local Group’ is part of a cluster of galaxies called Virgo of more than a thousand galaxies. And the Virgo cluster is just a small fraction of a much larger beast called the Local Supercluster also known as laniakea (‘big sky’ in Hawaiian). An immeasurable structure that houses about 100 thousand galaxies and with an apparent diameter of about 520 million light years.
Just as we arrived at Laniakea, the supercluster in which we live, it must be said that there are many others out there in the deep Universe. But due to the presence of dark energy, these amazing structures are just phantoms dissolving before our very eyes.
laniakea
The birth of the Universe
Since the birth of the Universe as we know it some 13.8 billion years ago with the explosion of the Big Bang, there was a primordial soup containing matter, antimatter, radiation, and probably many more particles and fields than we know now. With such a mixture of agents doing their thing, the Universe did not settle in a homogeneous way. Rather, there were small imperfections in the distribution of matter and energy.
In the midst of all this, there was a permanent cosmic competition between two phenomena. On the one hand, the expansion of the Universe and on the other, gravity that shapes everything we know, causing matter to clump together in different ways. This is how the first stars began to form. After hundreds of millions of years, the first galaxies began to clump together and then the merger of clusters.
Over time the cosmic web begins to take shape, with filaments of dark matter tracing a series of interconnected lines. It must be said that dark matter is responsible for driving the gravitational growth of the Universe, while normal matter interacts through different forces that result in the accumulation of gas.
Drifting Ghostly Collections
With the passage of time, the space between the filaments of this cosmic network yields its matter to the surrounding structures, becoming great voids. It is a game that allows even bigger structures to be formed, what we know as galactic superclusters, such as Laniakea. But contrary to what we might think, matter does not go in the same direction. That is, in such a case it would end up grouping itself in the same structure until it collapsed again. Contrary to this, dark energy causes the recession of distant galaxies that accelerates as the eons pass. Here the great gaps that separate the groups of matter also arisewhich are tremendously underdense.
Although we can now say that we belong to a supercluster of galaxies called Laniakea, the truth is that all the clusters within it are not gravitationally bound. Just as other galaxy clusters within their hyperclusters are not. That is, as time passes, every supercluster known today will eventually dissociate. The great collections of galaxies and quasars that seem so real will at some point become part of the ephemeral and will temporarily disappear. Billions of years from now the superclusters will be torn apart by the expanding Universe. Its galactic inhabitants will end up as lonely islands in an immeasurable ocean.
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