At the beginning of September 2014, the journal Nature published an article in which an international group of astronomers led by R. Brent Tully, from the University of Hawaii, showed which supercluster our galaxy, the Milky Way, belongs to. Until then astronomers had placed us in the Virgo supercluster but now it seems that we belong to a new, even larger superstructure named Laniakea, a Hawaiian word meaning ‘immeasurable (akea) sky (lani)’.
And it is certainly immeasurable: it is 520 million light-years in size, it is home to more than 100,000 galaxies similar in size to the Milky Way – along with an indeterminate number of smaller ones – containing a total of one thousand billion suns. “We have finally established the limits that define the supercluster of galaxies that we can call home,” said the North American astronomer.
This research once again highlights the peculiar large-scale structure of our universe. In fact, if there was one word to describe it, it would be “sparkling”. Harvard astrophysicist Margaret Geller explained it in a memorable phrase: “The local universe is like a sink full of water with dish soap.”
All these observations lead us to two conclusions: that there are large structures in the universe and that it is not very clear to decide what they are. The first is simple and helps us understand the hierarchy of the universe: stars are grouped into galaxies, and these into clusters. Curiously, these have not been formed in solitary regions but in the company of others. In fact, many of them seem to extend to the next cluster in the same way that cities extend to join others. In this way, hundreds of galaxies form bridges or thin sheets between clusters creating larger structures: superclusters, which contain at least a thousand billion suns in mass.
If things were like this, everything would be very simple, but the universe always has an ace up its sleeve to end up confusing everything. Without having to go very far, our entire local universe, made up of a hundred thousand galaxies, a thousand billion suns, is heading towards a point located in the direction of the constellations of Hydra and Centaurus at a speed of 600 km/s , more than two million kilometers per hour. There is a gravitational anomaly known as the Great Attractor, which contains a mass of 10,000 billion suns and whose center is between 150 and 250 million light-years from us.
Now some astronomers think that the Milky Way isn’t being pulled just by the Great Attractor, but by a much more massive region behind it: the Shapley Concentration , a collection of 17 galaxy clusters about 650 million of light years And not only that, but looping the loop, others defend that there may be something even more massive behind Shapley, since according to them the movement of the Local Group cannot be explained by invoking only the joint gravitational pull of the Great Attractor and the supercluster of Shapley.
But the surprises do not finish here, Looking across the Great Attractor, 250 million light-years from the Solar System, there is a huge cosmic sheet of paper, the Great Wall (today Coma Wall or CfA2 Great Wall). It is a wall of galaxies of Homeric dimensions: a filament of galaxies 200 million light-years away and whose dimensions are 500 million light-years long, 330 million wide and “only” 15 million light-years thick. . Can something like this really exist in the universe? It seemed that way until 2011, when doubts began to arise that in reality it is not a true gravitationally bound structure but a casual alignment of three smaller ones.
Fortunately or unfortunately, the universe has continued to surprise astronomers, who have been finding ever-increasing walls. One of them is the Great Wall of Sloan, almost 2.75 times larger than that of Coma. It is 1.38 billion light-years long and 1 billion from us. Its size is frightening: its diameter is 1/60 of the visible universe. But the best is for last: against all odds there is still a bigger structure, the Hercules-Corona Borealis Great Wall . It is a true monster, something inconceivable. It measures more than 10 billion light-years long, 7.2 billion light-years wide and 700 million thick, and was discovered in November 2013 thanks to the Swift, Fermi, Compton, BeppoSAX and INTEGRAL space telescopes.
Astronomers have needed a coaster for his lower lip because it has left them speechless. How can there be a structure that occupies, on its longest side, the ninth part of the visible universe? There is no theory to explain its existence. So much so that the astronomer Jon Hakkila has said that this wall “should not be there, but it is there” .
