Surprise Surprise! Stars Moving into Another Galaxy

8 February 2023

Life is unpredictable, and you never know when the next exciting adventure comes knocking at your door. Sometimes it might require you to pack your bags and move to another town or a new country altogether. Guess what! You are not alone: stars do it, too! 

For the first time, a team of astronomers at NSF’s NOIRLab found exciting new clues showing many stars moving into Andromeda Galaxy, the Milky Way’s nearest neighbour. Just like a flock of birds migrating to another place for food and shelter. 

Over billions of years, galaxies grow and evolve making new stars in the process. Sometimes two galaxies can even clash and ‘merge’ with other galaxies to become one. Scientists call this process a “galactic immigration”. 

By studying how each star moves through a galaxy and its outer halo, astronomers can explore the roots of these galactic immigration events. For example, where the stars in a galaxy originally came from, how they move to a different galaxy and so on. Such studies have only been possible in our own galaxy, the Milky Way, until now. 

Using the Dark Energy Spectroscopic Instrument (DESI) on the Nicholas U. Mayall 4-meter Telescope at the Kitt Peak National Observatory, Arizona (USA), astronomers did a similar study. By measuring the movement of nearly 7500 stars in the inner halo of the Andromeda Galaxy, the team saw patterns confirming that these stars came from another galaxy. Not only that, astronomers also found that this galactic immigration event took place about 2 billion years ago.

Having found this rich historical evidence, astronomers now aim to explore more stars lying in the outskirts of the Andromeda galaxy. In this way, they can study the structure and the journey of stars between galaxies in great detail.

Image: Striking new evidence for a mass immigration of stars into the Andromeda Galaxy has been uncovered by researchers led by astronomers at NSF’s NOIRLab. Each of the dots on this image represents an individual star in the Andromeda Galaxy, with the motion of the star (relative to the galaxy) colour-coded from blue (moving toward us) to red (moving away from us).Credit:KPNO/NOIRLab/AURA/NSF/E. Slawik/D. de Martin/M. Zamani

Cool Fact

Did you know that most of the stars in the Milky Way’s halo were formed in another galaxy? The stars later migrated into our galaxy when both the galaxies merged some 8 to 10 billion years ago. Galaxies like our Milky Way are constructed from the building blocks of many smaller galaxies in the cosmos over billions of years.