Max Planck Institute for Solar System Research | 2020 Jan 13
A single star has provided information about the collision of the Milky Way with the dwarf galaxy Gaia-Enceladus. The event likely took place approximately 11.5 billion years ago.
The dwarf galaxy Gaia-Enceladus collided with the Milky Way probably approximately 11.5 billion years ago. A team of researchers including scientists from the Max Planck Institute for Solar System Research (MPS) in Germany for the first time used a single star affected by the collision as a clue for dating. Using observational data from ground-based observatories and space telescopes, the scientists led by the University of Birmingham were able to determine the age of the star and the role it played in the collision. ...A snapshot from TESS of part of the southern sky showing the location of ν Indi (blue
circle), the plane of the Milky Way (bottom left) and the southern ecliptic pole (top).
These snapshots come from data collected in TESS observing sectors 1, 12 and 13.
Credit: J. T. Mackereth
On cosmic time scales, the colliding and merging of galaxies is not uncommon. Even if both galaxies involved are of very different sizes, such a collision leaves clear traces in the larger one. For example, the smaller galaxy introduces stars with a different chemical composition, the motion of many stars is altered, and myriads of new stars are formed.
The Milky Way has encountered several other galaxies in its 13.5 billion-year history. One of them is the dwarf galaxy Gaia-Enceladus. To understand how this event affected our galaxy and changed it permanently, it is important to reliably date the collision. To this end, the researchers led by Prof. Dr. Bill Chaplin of the University of Birmingham turned their attention to a single star: ν Indi is found in the constellation Indus; with an apparent brightness comparable to that of Uranus, it is visible even to the naked eye and can be easily studied in detail. ...
New Insights into Ancient Collision Between Two Galaxies
Keele University | 2020 Jan 13
Age Dating of an Early Milky Way Merger via Asteroseismology of the Naked-Eye Star ν Indi ~ William J. Chaplin et al