Free Astronomy Magazine July-August 2019

44 JULY-AUGUST 2019 SPACE CHRONICLES by IAC A system of globular clusters in the disc of a galaxy G lobular clusters are clusters of between a hundred thousand and a million stars, whose components have all roughly the same age, and have similar chemical composition. They are very old objects, formed some 11,500 million years ago, 2,300 million years after the Big Bang. These clusters are normally found in large galax- ies, distributed in their halos, in a spherical conformation around their centres. An international piece of research, led by a group from the National Autonomous University of Mexico (UNAM) and carried out with the OSIRIS instru- ment on the Gran Telescopio Canarias (GTC) has discovered in the spiral galaxy Messier 106 (also known as M106, and NGC 4258) globular clusters which, instead of being dis- tributed in a sphere, appear to be arranged in a disc aligned with the disc of gas in the galaxy and rotating at approximately the same velocity at this disc. “This has never been seen before, it is one of those totally unexpected and surprising findings which occur in science,” explains Rosa Amelia González Lópezlira a researcher at the Instituto de Radioastronomía y Astrofísica (IRyA- UNAM), who has led this work. “The way these clusters move, and their distribution is similar to the discs of galax- ies during the period of maximum star formation rate, some 10,000 million years ago, which is known as ‘cosmic noon’, so that we think that the disc of clusters in M106 could be a remnant from that epoch” The data obtained with the OSIRIS instrument, on the GTC at the Roque de los Muchachos Observatory have been of key importance, above all to confirm the candidates for