Free Astronomy Magazine January-February 2025

18 JANUARY-FEBRUARY 2025 ASTRO PUBLISHING As imaging techniques have im- proved, piercing ever more deeply into space, astronomers have been able to look closer and closer at these ‘island Universes’ to deduce what they might be like. For in- stance, researchers have observed powerful electromagnetic energy emanating from the heart of NGC 1270, suggesting that it harbors a frantically feeding supermassive black hole. This characteristic is seen in around 10% of galaxies and is de- tectable via the presence of an ac- cretion disk — an intense vortex of matter swirling around and gradu- ally being devoured by the central black hole. It’s not only the individual galaxies that astronomers are interested in; hints at many ongoing mysteries lie in their relationship to and interac- tions with one another. For example, the fact that huge groups like the Perseus Cluster exist at all points to the presence of the enigmatic sub- stance we call dark matter. If there were no such invisible, gravitation- ally interactive material, then as- tronomers believe galaxies would be spread more or less evenly across space rather than collecting into densely populated clusters. Current theories suggest that an invisible web of dark matter draws galaxies together at the intersections be- tween its colossal tendrils, where its gravitational pull is strongest. Although dark matter is invoked to explain observed cosmic structures, the nature of the substance itself remains elusive. As we look at im- ages like this one, and consider the strides made in our understanding over the past century, we can sense a tantalizing hint of just how much more might be discovered in the decades to come. Perhaps hidden in images like this are clues to the next big breakthrough. How much more will we know about our Universe in another century? A bove and below: NGC 1270 is just one member of the Perseus Cluster, a group of thousands of galaxies that lies around 240 million light-years from Earth in the constellation Perseus. Images such as those taken with the Gemini Multi-Object Spectrograph (GMOS) on the Gemini North telescope, one half of the International Gemini Observatory, which is supported in part by the U.S. NSF and operated by NSF NOIRLab, captures a dazzling collection of galax- ies in the central region of this enormous cluster. [Images and Videos: Interna- tional Gemini Observatory/NOIRLab/NSF/AURA/N. Bartmann (NSF NOIRLab) − Image Processing: J. Miller & M. Rodriguez (International Gemini Observatory/ NSF NOIRLab), T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), M. Zamani (NSF NOIRLab) − Ack.: PI: Jisu Kang (Seoul National University) − Music: Zero-project - Through the Looking Glass (zero-project.gr) ] The nature of these mysterious ob- jects and the size of the Universe were the subjects of astronomy’s famous Great Debate, held in 1920 between astronomers Heber Curtis and Harlow Shapley. The debate re- mained unsettled until 1924 when Edwin Hubble, using the Hooker Tel- escope at Mount Wilson Observa- tory, observed stars within some of the nebulae to calculate how far they were from Earth. The results were decisive; they were far beyond the Milky Way. Astronomers’ notion of the cosmos underwent a dramatic shift, now populated with innumer- able strange, far-off galaxies as large and complex as our own. n