3/25/2023 0 Comments Globular clustersThis makes it especially interesting: a low-density, fluffy GC like Pal 5 is more vulnerable to tidal disruption. Although there is no direct observation of black holes in Pal 5, it has long stellar streams and is the least dense of all the Milky Way GCs. The authors of today’s paper focus on a particular Milky Way GC called Palomar 5 (Pal 5). ![]() Thus it is completely reasonable to ask the question, what is the role they play in the life of a GC? The most massive stars quickly evolve to become black holes. GCs are expected to have some high mass stars and some low mass stars according to the initial mass function ( IMF ). These black holes are named stellar mass black holes, to be distinguished from the supermassive black holes sitting in the center of galaxies. How can star clusters have black holes? Massive stars (much higher than 10 solar mass) eventually become black holes at the end of their lives. But wait! The authors of today’s paper investigate the possible role of stellar mass black holes in this story. You may think that that’s because the original GCs completely dissolved. When the stars get spread into a stellar stream, what happens to the original GC? Astronomers know of a dozen stellar streams from tidally stripped GCs, but very few progenitors have been observed. GCs entering the strong gravitational field of the Milky Way may experience tidal stripping and lose some of their stars. According to this picture, some GCs in our Galaxy were born in external galaxies and merged into the Milky Way later. In standard galaxy formation theory, galaxies like our Milky Way formed through the hierarchical merging of many smaller galaxies. Globular clusters (GCs) consist of hundreds of thousands of tightly bound stars, and we have around one hundred in our Milky Way galaxy. ![]() In today’s paper, we will embark on a journey through the life of globular clusters. To astronomers, though, globular clusters are fascinating because they are relics of the early universe, carrying signatures from their creation through billions of years (see this astrobite ). ![]() That is the reason they are a favorite target at star parties. Compared to the faint fuzzy patches of external galaxies and Milky Way nebulae, globular clusters glow like millions of jewels crowded together. If you have ever looked through a telescope at Messier Objects, you’ll agree with me that globular clusters are absolutely stunning. Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona (IEEC-UB), Barcelona, Spain. Title: A supra-massive population of stellar-mass black holes in the globular cluster Palomar 5Īuthors: Mark Gieles, Denis Erkal, Fabio Antonini, Eduardo Balbinot, and Jorge Peñarrubiaįirst Author’s Institution: 1.
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