Lee Jae-woo
Professor of Sejong University |
By Kim Tong-hyung
Staff Reporter
Scientists have made progress in breaking down the complicated picture of how globular clusters, the compact groups of ancient stars found in the Earth's local part of the cosmos, originated and evolved.
The new findings may lead to advancements in the studies on the evolutionary secrets of the Milky Way, researchers said.
In a study published in a peer review journal, Nature, a team of scientists led by Sejong University's Lee Jae-woo and Kang Young-woon said they had confirmed differences in the chemical composition of stars in many of the stellar cities.
"This represents a further challenge to the current theories on stellar evolution, which mostly consist of analytic models based on the presumption that stars within a single globular cluster are identical in mass, age and chemical elements," Lee said.
Since they appear to contain some of the first stars produced in the galaxy, the study on the origins of globular clusters and their role in galactic evolution is considered critical for the research on star formation and estimations on the age of the universe.
Stars in globular clusters have been found to differ in chemical composition from most stars in the galactic disk. And the predominant belief in science was that all stars in most clusters have very similar chemical compositions, although the compositions differ from cluster to cluster.
However, there have been findings about differences in light chemical elements among stars in the same clusters since the 1970s, and the current study by Lee's team further drives the point home by identifying variations in heavy elements.
Lee's team observed the stars in about 40 globular clusters for 100 days in 2006, using a 1-meter diameter telescope and calcium imaging filters of the National Radio Astronomy Observatory in Virginia, United States.
After analyzing the data, the researchers found that the calcium composition among stars differed in more than 50 percent of the clusters.
``The differences in heavy elements can't be explained by abnormalities in chemical reactions during the star's formation. This rather adds to the theory that the stars in globular clusters have originated and evolved from substances of various compositions of heavy chemical elements,'' Lee said.
``It could be said that our findings support the thinking that the globular clusters in the Milky Way haven't originated from our own galaxy. They instead look to be the remains of the dwarf galaxies that were sucked and integrated into our galaxy.''
Unlike the light elements in stars, such as hydrogen, deuterium, helium and lithium, which are believed to have been produced by the nuclear reaction in stars, the formation of heavier elements is explained by supernova explosions.
It would take a lot more than the gravity of globular clusters to bound the remains of the supernova explosions and allow them to evolve as new stars, although the mass of dwarf galaxies do provide enough pull to do so, Lee said.
thkim@koreatimes.co.kr
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