The Milky Way that we all know today was a very different galaxy in the very distant past. Scientists from the Instituto de Astrofísica de Canarias (IAC) have put a sequence to the events that created the Milky Way’s classic spiral shape. The scientists say that the universe of 13,000 million years ago was very different from what we know today.
In the very distant past, stars were forming at a very rapid pace to create the first dwarf galaxies. The mergers of those early dwarf galaxies gave rise the much more massive present-day galaxies such as our own. The scientists say that the chain of events that created our galaxy was unknown until now.
The team used exact measurements of the position, brightness, and distance of about a million stars of our galaxy that are within 6,500 light-years of the sun. The team then compared and analyzed theoretical models and the distribution of colors and brightnesses of the stars in the Milky Way. Using those measurements, the team split the stars into several components including the halo, described as a spherical structure that surrounds spiral galaxies, and the thick disc.
The team notes that past studies had found that our galactic halo showed signs of being made up of two distinct stellar components. One component was dominated by stars that were bluer than others. The team was able to identify the stars in the blue component as having belonged to a dwarf galaxy called Gaia-Enceladus that crashed into the early Milky Way. The team says that the epoch of the merger between our galaxy and Gaia-Enceladus and the red population was unknown until now.
The team says that the stars in the blue component have smaller quantities of metals in them than those in the red component. Those findings, along with the addition of the predictions of simulations analyzed by the team, allowed them to complete the history of the formation of the Milky Way. The scientists created a video that shows how they think our galaxy was formed, which can be seen above.