The Universe is not a large cloud but on a large scale, it is structured in large clusters of galaxies, and in voids. The nearest voids have just been mapped, up to 700,000 light-years around us. And other researchers track them on a very large scale.
Le billet science du weekend dives today into the vacuum bubbles of the cosmos with the details of Mathilde Fontez, editor-in-chief of the scientific magazine To epsilon.
franceinfo: A team has just mapped the 7 cosmic voids closest to us, are we starting to “see” the voids in the universe?
Mathilde Fontez: It seems a bit contradictory: seeing the voids, looking where there is nothing, no light. We are more accustomed to hearing regarding very bright stars and galaxies. But there are also voids in the universe, between galaxies, between clusters of galaxies: areas where nothing happens, but which can be considered as true astronomical objects.
And indeed, the team of astrophysicist Hélène Courtois, at the University of Lyon, specializing in the cartography of the universe, has just published a map of the voids around our galaxy, the Milky Way, and up to 700 000 light years.
What do these voids look like?
To bubbles: to empty pockets delimited by filaments of galaxies. It should be remembered that in the Universe, the galaxies are not distributed randomly: they are gathered in clusters, which are concentrated in a kind of network, filaments which form like a spider’s web – we speak of a cosmic web. . And between the filaments, there is emptiness.
Near the Milky Way, Hélène Courtois and her team find that the voids are more complex than expected, they have rather tortured shapes. And some of them are not completely empty: there are currents of galaxies inside. Other voids, on the other hand, are incredibly pure.
But it is above all the global properties of these voids that interest researchers: the shape of hundreds and hundreds of large-scale voids in the universe, over billions of years of distance.
Do we identify the voids in the universe?
It is a fairly new field of research : It’s only been ten years since telescopes that measure the positions of galaxies have collected enough data to reveal this cosmic network of clusters of galaxies. And so the voids. In total today, astrophysicists have identified nearly 6,000 voids.
But this number should soon explode: this mapping of voids is one of the subjects on the program of a mission which will start this summer, the Euclid space telescope, partly made in France. It will measure the position of 50 million galaxies, and find hundreds of thousands of voids. With these measurements, astrophysicists hope to understand the expansion of the Universe, and why it is accelerating.
