Cosmic collisions, though tumultuous, are indispensable. Their repercussions could potentially unravel the existence of mankind.
In the constellation Corvus, approximately 45 million lightyears away, a captivating dance unfolds between two massive galaxies known as the Antennae Galaxies. These celestial bodies are in the process of merging, a cosmic event that has been shaping the universe since its inception.
Galaxies, vast collections of stars, gas, dust, and a mysterious substance called dark matter, are held together by the force of gravity. This gravitational attraction leads them to move towards each other and eventually collide, a phenomenon that plays a crucial role in the history of the universe.
The majority of a galaxy's mass is in the form of dark matter, a substance that astronomers can't see directly but can detect through its gravitational effects, such as gravitational lensing. This influence is evident in the Antennae Galaxies, where the dark matter's presence can be felt as the galaxies slowly spiral towards each other.
Gravitational wave astronomy is still in its infancy, but it holds great promise for the future. To detect gravitational waves from supermassive black hole (SMBH) mergers, we will need a bigger experiment like the Laser Interferometer Space Antenna (LISA). Black hole marriages could open the door to exploring galaxy mergers that are too faint to see with ordinary telescopes through the detection of gravitational waves.
Galaxy mergers can lead to epic bursts of star formation, as the colliding galaxies' star-forming regions collide and combine. However, these events can take a billion years to finish, a blink of an eye in the universe's 13.8-billion-year history.
During mergers, stars within a galaxy are typically hundreds of billions to tens of trillions of kilometres apart. Yet, debris is ripped out of galaxies during mergers and strewn into long strands of stars, creating a cosmic spectacle.
Major galaxy mergers occur when the two entwining objects are of roughly equal size, while minor mergers happen when a large galaxy gobbles up a tiny one. These events are an integral part of the Lambda CDM model, a current best model of the universe's size, structure, and origin.
However, as galaxies merge, so do their black holes. This process, known as the Final Parsec Problem, is a phenomenon that astronomers don't fully understand. When two galaxies merge, their black holes will eventually come close enough to each other to merge, creating a single, colossal black hole.
In the future, galaxy mergers may be prevented by dark energy, a factor that will eventually expand the universe at an ever-quickening pace, weakening the gravitational attraction between galaxies and pushing them further apart.
Without galaxy mergers, we probably wouldn't exist. These cosmic events have played a significant role in the formation of galaxies, stars, and planets, including our own Milky Way. So, the next time you gaze up at the stars, remember the dance of galaxies, black holes, and gravity that brought us here.
