Globular clusters are densely packed collections of around a million stars, some of which are the oldest stars in the universe.
Most large galaxies, including the Milky Way, host globular clusters. It is believed that the Milky Way also has between 150 and 180 of these star clusters.
Although the universe and galaxies within it has evolved over time, globular clusters are robust, and many remained intact for billions of years.
Globular clusters are thought to be almost as old as the Universe itself, which formed nearly 14 billion years ago with the Big Bang. Findings of a new research, however, challenge this idea.
The new research, which was published in the Monthly Notices of the Royal Astronomical Society on May 24, suggests that globular clusters could be 4 billion years younger than previously believed. The researchers said that these stellar clusters may be closer to 9 billion years in age.
Binary Star Systems
The researchers used Binary Population and Spectral Synthesis (BPASS) models, which have previously been used to determine the age of young star populations within the Milky Way and other extremely distant galaxies and to study binary star systems and their evolution. These stellar pairs, which lie within globular clusters, have long been thought to be as old as their clusters.
Using BPASS models, the researchers determined that the globular clusters that these systems are part of are not as ancient as other models have suggested.
"We reevaluate the properties of old stellar populations using a new set of stellar population synthesis models," the researchers wrote in their study.
"The best fitting model populations are often younger than those derived from older spectral synthesis models, and may also lie at slightly higher metallicities."
Implications On Current Understanding Of Galactic Formation And Evolution
Stellar clusters have been crucial in studying star evolution and answering questions about galactic formation and when the universe started. Star clusters, for instance, provided clues that the solar system was not located at the center of the Milky Way, which was thought of until the 1930s.
If globular clusters are indeed younger than previous estimates, the researchers said that this could change current understanding of how galaxies formed and evolved.
"It changes our picture of the early stages of galaxy evolution and where the stars that have ended up in today's massive galaxies, such as the Milky Way, may have formed," said study researcher Elizabeth Stanway, from Warwick's Astronomy and Astrophysics Group.