Scientists are building a better account of the lives of young stars, from their birth in collapsing clouds of cosmic gas and dust to when they “fly the nest” and move away from other young stars in their original clusters.
Studying these stellar timelines will help scientists better determine the age of stars — and since age is a major parameter in astrophysics it could eventually offer astronomers a clearer picture of how star systems and even entire galaxies evolve.
The team developed their new age determination method by using two of the most powerful and accurate techniques already used by astronomers to study stars. They discovered that one known as an isochron measurement can be used to determine exactly when stars are born. The other, known as dynamical tracking, provides information about when stars leave their space nests.
Synchronizing these two different cosmic clocks revealed to the team that the stars squeeze into their stellar siblings for about 5.5 million years after birth.
“Our work paves the way for future studies of star formation and provides a clearer picture of how stars and star clusters develop,” team leader Nuria Miret-Roig, an astrophysicist at the University of Vienna, said in a statement. “This is an important step in our efforts to understand the formation of the Milky Way and other galaxies.”
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Star chronometers
Until now, the best approximations of stellar age that scientists have for stars apply to stellar bodies found in star clusters, which are mostly the same age because they formed from the same collapsing cloud of dust and gas.
Miret-Roig and team applied isochronous measurement and dynamical tracking to six relatively close star clusters up to 490 million light-years away; these clusters are also relatively young at around 50 million years. They found that the isochron measurement gave an age 5.5 million years older than the dynamic backtracking.
“This shows that the two measurement methods are measuring different things,” Miret-Roig explained. The team theorizes that this is because the isochron clock starts ticking when stars are born, while the dynamical backtracking clock only kicks in when a cluster expands and individual stars begin to break away from their siblings. as well as from the clouds of gas and dust in which they were born.
“This age difference between the two methods represents a new and much-needed tool to quantify the earliest stages of a star’s life,” said study co-author and University of Vienna professor scientist Joao Alves. “Specifically, we can use it to measure how long it takes for baby stars to leave their nest.”
The synchronization of these two cosmic clocks and the discovery that the embedded phase lasts about 5.5 million years was made possible by data from European Space Agency Gaia space mission, which is currently building an extremely precise three-dimensional map of more than one billion stars in our Milky Way galaxy. The results were also aided by radial velocity measurements of stars from the ground-based APOGEE catalog.
“This discovery has significant implications for our understanding of star formation and stellar evolution, including planet formation and galaxy formation, and opens a new perspective on the chronology of star formation,” Alves said. “For example, one can estimate the duration of the so-called ’embedded phase,’ during which baby stars remain in the parent gas cloud.”
The team’s research was published Nov. 23 in the journal Nature Communications Natural astronomy.
