Research reveals new insights into ancient collision between two galaxies

A global research team, including Keele’s Dr Barry Smalley, has revealed new insights about an ancient collision between our galaxy and another billions of years ago through the forensic analysis of a single star.

The investigation by Dr Smalley and his colleagues uncovered these new insights into the collision between the Milky Way and another smaller galaxy called Gaia-Enceladus early in its history, all thanks to the analysis of a single star visible from the southern hemisphere.

The international team of scientists analysed the bright star v Indi, located in the constellation of Indus, which enabled them to investigate the history of the wider galaxy.

Because stars such as v Indi carry ‘fossilised records’ of their histories, scientists are able to forensically characterise them to gather information about the wider galaxy and the environments the star formed in.

In this study, published in Nature Astronomy, the team used v Indi’s natural oscillations to determine its age, using data from NASA’s Transiting Exoplanet Survey Satellite (TESS) which was launched in 2018 to survey stars across the sky and any planets orbiting them.

This data, combined with information obtained by the European Space Agency’s (ESA) Gaia mission, revealed that the star was born early in the Milky Way’s life around 11.5 billion years ago, but its motion through the galaxy was altered when the Milky Way collided with Gaia-Enceladus.

Senior Lecturer in Astrophysics Dr Smalley said: “This exciting study, using observations from both space and ground-based observatories, has provided us with a more precise date of when the smaller Gaia-Enceladus galaxy was swallowed by the young Milky Way. While this occurred over 10 billion years ago, the evidence is still strewn across the night sky, allowing us to piece together events that happened early in the history of our Galaxy.”