The Yonsei-Sejong University Research Team Revealed Our Galaxy’s 10 Billion Years Past Yonsei’s research team, together with Sejong University’s team, discovered for the first time in the world that our galaxy was composed of 70 different galaxies before 10 billion years. At the time, other galaxies located outside of our galaxy were absorbed into ours. They were shrunk to star clusters. Now our galaxy is made of about 150 known globular clusters. Professor Lee Young-wook from Yonsei’s Department of Astronomy and Professor Lee Jae-woo from Sejong University’s ARCSEC (Astrophysical Research Center for the Structure and Evolution of the Cosmos) published the result of their research in November issue of Nature with Professor Kang Young-woon and Researcher Lee Jin-a from Sejong University. The research team examined information about calcium spurted from star clusters in our galaxy. From the information, they made an observation that many star clusters had different types of information regarding calcium while they should have had the same information if they were within the same galaxy. The team made the discovery only using a small telescope with 1-meter diameter, while other American and European researchers were using 10-meter class telescopes. “The discovery that our galaxy has become today’s condition absorbing galaxies exterior to ours made it inevitable to approach the origin of our galaxy from a new perspective.” Star clusters are groups of stars. Among the two types of star clusters, globular clusters are spherical concentrations of approximately ten thousand to one million old stars. Until this new discovery, stars in globular clusters had been thought to be the stars with same chemical composition and age. Globular clusters are playing an important role in studying the age of the universe, the formation of galaxies, evolution of stars and other issues on our universe. From 1970s, there were discoveries on small differences of chemical elements among stars in globular clusters in our galaxy. The revelations were hard to explain using the model which presumed the same age and chemical composition of stars in globular clusters. They probed 40 globular clusters and the core region of our galaxy for 100 days in 2006, using one-meter telescope at Cerro Tololo Inter-American Observatory in Chile and calcium filter. After the analysis of their probing, more than 50% of globular clusters in our galaxy showed a wide variety in percentage of calcium they contain, opposing the existing hypothesis that most of globular clusters have the same amount of heavy elements. As it is not possible to explain this in terms of imperfect element compound at the time of birth of the globular clusters, it can only mean that the stars in the globular clusters were generated from various matters with different compound of heavy elements through chemical evolution taking place through many generations. The result of the research is a pivotal discovery that will change the existing paradigm on globular clusters, and a proof of the team’s theory was published in Astrophysical Journal in 2005 and 2007.