Astronomers at the Netherlands Research School for Astronomy have found that a globular cluster NGC 2005, a spherical collection of stars tightly bound by gravity in the Large Magellanic Cloud, a smaller neighbouring galaxy to the Milky Way, is actually a relic of the merger of a smaller galaxy into the LMC. According to the study that was published on October 18 in Nature Astronomy, NGC 2005 possesses a chemical composition very different from the other 10 globular clusters of the LMC studied by the researchers. The globular cluster, which is located some 750 light-years away from the LMC’s centre and contains about 200,000 stars, contains less silicon, zinc, calcium and copper than the other ten clusters, indicating that the cluster was not formed during the formation of the galaxy but acquired from a neighbouring smaller galaxy during a merger. In the smaller galaxy, which scientists believe merged into the LMC, stars might have formed slowly.
During the merger, small stars of the galaxy were pulled apart and scattered while the big central globular cluster NGC 2005 survived the merger finding its new home in LMC. “We have now convincingly demonstrated for the first time that small galaxies neighbouring our Milky Way have in turn built up from even smaller galaxies,” said David Messari, an astronomer at the University of Groningen, Italy, in a statement. Messari is also one of the authors of the research.
Scientists already know that large galaxies do not spare each other if they have stronger gravitational power than their neighbours. Many unusual galaxies also participate in a gravitational tug-of-war to gain more star material. But the study shows that even the small galaxies were capable of absorbing galaxies smaller than them.
According to the scientists, one of the interesting things is that when the merger happened, LMC would have been much smaller than it is now. The LMC is 14,000 light-years in diameter, which is 3.7 times smaller than our Milky Way galaxy. Our Milky Way has 150 known globular clusters which are older than open star clusters and stretch our galaxy’s age back to 13.5 billion years.
