Is This Group of Milky Way Stars Invaders, or Just Poor Victims? (Study)

milky way

A group of Milky Way stars initially believed to be invading galaxies might actually be local stars.

What were once classified as invaders are now known to be nothing more than friends long gone, as a collection of stars on the outskirts of our galaxy have been discovered to have originated from within the Milky Way rather than from outside it.

Invading Stars Established to be Group of Milky Way Stars


Scientists have spent the last five years observing a group of stars clustered together at the edge of the galaxy. This group of Milky Way stars was clustered in such a way that they seemed unnatural.

Namely, they exceeded the boundary of the galactic disk (the furthest edge of the galaxy itself). Instead, this group orbited in a circle far too close together to appear natural. Additionally, several such stars were observed to be floating in positions both above and below the galactic disk. This is not a typical phenomenon.

The leading theory over these past years was that these stars were leftovers from smaller galaxies that integrated with our own, something that has happened every so often. Smaller galaxies like these would be torn apart and incorporated into the Milky Way due to its stronger gravity, with certain remnants like these star clusters left outside.

However, Columbia University Professor of Astronomy Kathryn Johnston, one of the researchers studying this star cluster, determined that this was not the case. Rather than the remnants of invaders, these stars reportedly once belonged to the Milky Way.

By observing a variety of stars in the galactic disk and galactic halo (the area around a galaxy itself), it was determined that this type of stars as well as what they are made of are more consistent with similar space bodies from the disk itself rather than those from other invading galaxies.

For this reason, it was concluded that they must have been ejected by smaller galaxies as these tried to enter our own.

A confirmation of this fact could help offer a better look at what happens when our galaxy collides with others. It might also present us with a clearer picture of what stars in different galaxies are made of.

A paper with the current study results is available in the journal Nature. The study team’s next target will be to try and establish precisely when this collision might have occurred.


Image Source: NASA/JPL