Galaxies similar to the Milky Way, spirals, are rarer in our environment than they should be
Towards the middle of the 20th century, astronomers realized a strangeness in the environment of the universe known as the Supergalactic Plane, an immense region in our cosmos where our own galaxy is located: the absence of galaxies similar to ours.
Searching for galaxies like ours. Now, an international team of researchers has found a possible explanation for this lack of galaxies like ours in our immediate environment. Those responsible for this phenomenon would be collisions between galaxies.
Spirals vs. ellipses. Our galaxy is a spiral galaxy. This type of galaxy is characterized by having a disk shape, with a marked galactic core and arms that extend in a spiral between the galactic center and the periphery of the disk.
The lack of these galaxies contrasts with the relative frequency with which elliptical galaxies can be found, galaxies similar to ours, with an elliptical shape but without a marked internal structure.
Supergalactic Plane. Locating our galaxy in the immensity of the known universe is a complex task. Our galaxy is located in a group of galaxies called the Local cluster, located in a region with a certain density of galaxies called the Virgo supercluster, in turn located in the Laniakea supercluster. If we move our perspective further away we will come across this “Supergalactic Plane”.
This supercluster extends over more than 500 million light years (approximately 160 megaparsecs). The supergalactic plane is a flattened structure (as its name suggests), which extends for a distance of about 1,000 million light years with a high density of galaxies.
In this plane some galaxies are missing, specifically the galaxies most similar to our Milky Way, the spiral galaxies.
13.8 billion years in a simulation. To understand the dynamics that have affected this process, the researchers turned to a supercomputer simulation project called SIBELIUS (Simulations Beyond the Local Universe).
This simulation tries to reproduce the evolution of the great cosmological structures of the known universe. Among them, the Supergalactic Plane. The authors of the study recently published details of the process followed in an article in the journal Nature Astronomy.
Crashes and more crashes. What the simulation showed the researchers was the most plausible explanation for this enigma: that the greater density of galaxies implied an increase in the frequency with which they collided.
The collisions and interactions between galaxies “disorder” the elliptical galaxies, transforming them into ellipticals, thus making this second group more prominent where the density is greater.
A mystery among many. That of the galactic plane and the absence of galaxies like ours in our “near” environment is just one of the many enigmas that plague modern cosmology. However, as Till Sawala, one of the authors of the study, explains, this mystery was one of those that caught the attention of Nobel Prize winner Jim Peebles, who included it in his list of cosmic anomalies.
This fact was what inspired Sawala to investigate this mystery and what ultimately led his team to answer a question that had been intriguing astronomers around the world for decades.
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Image | NASA, ESA, CSA, Rogier Windhorst (ASU), William Keel (University of Alabama), Stuart Wyithe (University of Melbourne), JWST PEARLS Team, Alyssa Pagan (STScI).