The Milky Way grows by 'eating' smaller neighboring galaxies.

Galactic cannibalism is a fundamental process in the evolution of the universe. The Milky Way has a mass of approximately 1.5 trillion solar masses, which exerts a powerful gravitational influence on its surroundings. According to data from the Gaia space telescope mission launched by the European Space Agency in 2013, our galaxy has absorbed several smaller systems over billions of years. Evidence for this exists in 'stellar streams,' which are the shredded remains of captured galaxies.One of the most prominent examples is the Sagittarius Dwarf Spheroidal Galaxy, which was discovered in 1994 by Rodrigo Ibata and his colleagues. This galaxy is currently being stripped of its stars as it orbits the Milky Way. Researchers have also identified the 'Gaia-Enceladus' event, a major collision that occurred roughly 10 billion years ago and helped shape the thick disk of our galaxy. These mergers provide the gas and stars necessary for the Milky Way to continue its growth.The most significant future event is the predicted collision with the Andromeda Galaxy (M31). NASA astronomers using Hubble Space Telescope data have determined that Andromeda is approaching us at about 250,000 miles per hour. In approximately 4 billion years, the two will begin a complex merger process. This will eventually result in a single, massive elliptical galaxy often referred to by astronomers as 'Milkomeda.'