Galaxies may look serene and otherworldly in all those NASA photos, but how they actually came into being was the total opposite. A new study, published in the journal Nature Astronomy, has traced the influence these galactic crashes have had on the Milky Way, and found that one of them coincided with the birth of our Sun around 4.7 billion years ago. The study is based on data gathered by Gaia, a space observatory launched by the European Space Agency (ESA) in 2013 to survey the stars of the Milky Way. As it looked onto the stars, Gaia discovered that the ripples caused by the Sagittarius galaxy crashing into the Milky Way triggered an uptick in star formation.
Just how complex the Milky Way actually is remained unknown until Gaia shed more light on it through 3D maps of the entire galaxy and the positions of its stars. The problem with previous conclusions about our galaxy’s star formation history is that they either focused on just the solar system and its close surroundings or were unable to isolate the star formation events that made the Milky Way what it is now.