The findings come from a study of globular clusters by NASA and the European Space Agency using data from the Hubble Space Telescope and published in the journal Nature.
"Our observations of star clusters have shown us that, although they all formed over ten billion years ago, some of them are still young at heart," study co-author Steinn Sigurdsson at Penn State said. "We now can see how fast the clusters are racing toward their final collapse.
"It is as if each cluster has its own internal clock, some of which are ticking slower than others," he said in a Penn State release.
Globular clusters are spherical collections of stars, tightly bound to each other by gravity, and the approximately 150 globular clusters in the Milky Way contain many of our galaxy's oldest stars, scientists said.
"Although these clusters all formed billions of years ago, we wondered whether some clusters might be aging faster or slower than others," Francesco Ferraro of the University of Bologna in Italy, the leader of the study team, said.
"By studying the distribution of a type of blue star that exists in the clusters, we found that some clusters had indeed evolved much faster over their lifetimes, and we developed a way to measure the rate of aging."
In certain circumstances, stars within a cluster can be reinvigorated and given a new burst of life, creating the observed blue stars, the researchers said.
"Stars can receive extra fuel that bulks them up and substantially brightens them if one star pulls matter off a neighbor, if two neighboring stars merge together, or if two stars collide," Sigurdsson said.
"This study provides the first evidence, based totally on data from observations, of how quickly different globular clusters age."