Terzan 5 is a living fossil from the early days of the Milky Way. NASA/ESA/Hubble/F. Ferraro A dense cloud of stars in the middle of the Milky Way could reveal a lot about our galaxy’s past.

The cluster is called Terzan 5 and Italian researchers have found evidence that it could be the same as the building blocks that made up our galaxy, because of the striking similarity of its stars to the most ancient ones in the Milky Way.

Terzan 5 lies 19,000 light-years away from Earth, and there are two kinds of stars within it, which differ in the elements they contain and have an age gap of around 7 billion years; some were formed 4.5 billion years ago and others are far older, forming as long as 12 billion years ago.

According to the team, this group of stars — known as a globular cluster — is unlike any they have identified before, and they have named it a living fossil from the formation of the Milky Way.

While other stars dissolved and merged to form our galaxy, Terzan 5 managed to survive and so still exists as a relic of this early process.

"We think that some remnants of these gaseous clumps could remain relatively undisrupted and keep existing embedded within the galaxy," said Francesco Ferraro, lead author of the study from the University of Bologna. "Such galactic fossils allow astronomers to reconstruct an important piece of the history of our Milky Way."