Astronomers Discover A Rare Relic Of The Early Milky Way

Terzan 5 is a large collection of gravitationally bound stars located 19,000 light-years away from us, towards the bulge of our galaxy. Although it was discovered almost 50 years ago, the new research indicates that it is made of at least two distinct populations of stars that formed in two separate bursts roughly 7 billion years apart. A paper detailing the discovery is published in the Astrophysical Journal, and is available online. 

“This requires the Terzan 5 ancestor to have large amounts of gas for a second generation of stars and to be quite massive. At least 100 million times the mass of the Sun,” said Davide Massari, co-author of the study, from INAF, Italy, and the University of Groningen, Netherlands, in a statement.

This incredible property makes Terzan 5 a crucial clue in our understanding of how galaxies form. Its older stellar population is very similar in age and composition to the stars found free floating in the galactic bulge, and the presence of a second star population reveals that the cluster was able to survive undisturbed for billions of years. Studying Terzan 5 is like looking back in time at the building blocks of the Milky Way.

“Some characteristics of Terzan 5 resemble those detected in the giant clumps we see in star-forming galaxies at high-redshift, suggesting that similar assembling processes occurred in the local and in the distant Universe at the epoch of galaxy formation,“ explained lead author Francesco Ferraro of the University of Bologna.

This assessment of Terzan 5 opens the door to a novel understanding of the turbulent past of the Milky Way and could also provide potential clues on how other galaxies formed in the early universe.