Unlike the Milky Way, there aren't many spiral galaxies in the Supergalactic Plane where we are. Finally, astronomers believe they understand why galaxies similar to ours are so uncommon.
It is strangely difficult to find galaxies similar to our Milky Way in our cosmic backyard. Astronomers have finally been able to answer why thanks to new supercomputer simulations.
The Supergalactic Plane, a billion light-year-wide sheet known as a "supercluster," is where the Milky Way galaxy cluster is located. Large galaxy clusters are pinned to this sheet. However, bright elliptical galaxies are far more common along this massive plane than other spiral galaxies, which are surprisingly rare.
Astronomers now propose that the reason for this is that our neighborhood is covered in ellipses while our own galaxy is somehow spared from a violent history of frequent galactic collisions. Their results were released in the journal Nature Astronomy on November 20.
A physics professor at Durham University in the United Kingdom named Carlos Frenk said in a statement, "The distribution of galaxies in the Supergalactic Plane is indeed remarkable." "It is rare but not a complete anomaly: our simulation reveals the intimate details of the formation of galaxies such as the transformation of spirals into ellipticals through galaxy mergers."
With thousands of galaxies within, the local supercluster is a pancake-shaped formation made up of multiple massive galaxy clusters. The galaxies found in these clusters can be divided into two main types: spiral galaxies, such as our own, with many young stars still forming along their delicate spiral arms, and elliptical galaxies, which are filled with ancient stars and anchored by massive supermassive black holes.
However, scientists have been aware of the perplexing discrepancy since the plane was discovered in the 1950s by French astronomer Gérard de Vaucouleurs: while spiral galaxies were noticeably rare, the plane was teeming with bright elliptical galaxies.
The researchers behind the new study used a supercomputer simulation called Simulations Beyond the Local Universe (SIBELIUS) to study the evolution of our cosmic neighborhood. The scientists created a model that nearly replicated the plane's evolution by rewinding the observed galaxies' evolution back 13.8 billion years to the Big Bang.
The spiral galaxies in the dense clusters of the Supergalactic Plane often crashed into each other in catastrophic collisions, breaking their fragile arms and smoothing them out into elliptical galaxies, the researchers observed in their simulation. Additionally, this process increased the amount of matter that a supermassive black hole in a struck galaxy could hold, causing the black hole to grow even larger.
However, spiral galaxies that are located outside of the plane were largely spared from the cosmic bar fight, which allowed them to maintain their structural integrity. Spiral galaxies like our own continue to evolve in the chaotic plane despite this, but it does make them unique in that they have so far escaped the worst of the damage.