New research published on Monday, July 22nd has indicated that the Milky Way gobbled up a galaxy one quarter of its mass 10 billion years ago in a "violent collision" that did not fully settle for eons, as stated by astronomers, AFP reported.
Recent evidence suggests that our home galaxy, the Milky Way, is a cannibal, as it swallowed up a smaller galaxy, Gaia-Enceladus, during its early years, incorporating the galaxy's stars, gases and dust into its orbit. Nonetheless, an exact date for this "accretion event", as the astronomers say, has been hard to pin down. However, new research, from a collaboration of scientists in Europe, examined the ages of the stars across the Milky Way to more accurately determine how the galaxy formed, according to CNET.com.
Researchers from the Instituto de Astrofisica de Canarias (IAC) used the Gaia space telescope to take exact measurements of the position, brightness and distance of around one million stars in the Milky Way within 6,500 light years of the Sun. They identified two distinct stellar sets, one "bluer" and containing less metal, one "redder" containing more, AFP reported
After studying their movement and composition, the team determined that both sets of stars were equally old, but the bluer ones had been set into a "chaotic motion"; evidence of the Milky Way swallowing a smaller galaxy in the distant recesses of time.
In a statement to AFP, Carme Gallart, lead author of the study published in Nature Astronomy, has confirmed that the novelty of their work is that they have been able to assign precise ages to the stars that belong to the galaxies that merged and, by knowing these ages, they would be able to specifically decide when the merger took place.
According to Gallart, the next step for the astronomers is to extend the timeframes even further which should provide an even more accurate determination of how the Milky Way's disk came to be, stating, "Now we are working on the full evolution of the disk as a function of time, till the present, using the same technique to derive ages and chemical compositions of the stars," according to CNET.com
It is believed that the Milky Way contains at least 100 billion stars and its centre contains an intense radio source believed to be the supermassive black hole Sagittarius A*, AFP reported.