ESO Science Release | 2015 May 13
[img3="The giant elliptical galaxy Centaurus A (NGC 5128) and its strange globular clusters. (Credit: ESO/Digitized Sky Survey. Acknowledgement: Davide de Martin)"]http://cdn.eso.org/images/screen/eso1519a.jpg[/img3][hr][/hr]Observations with ESO’s Very Large Telescope in Chile have discovered a new class of “dark” globular star clusters around the giant galaxy Centaurus A. These mysterious objects look similar to normal clusters, but contain much more mass and may either harbour unexpected amounts of dark matter, or contain massive black holes — neither of which was expected nor is understood.
Globular star clusters are huge balls of thousands of stars that orbit most galaxies. They are among the oldest known stellar systems in the Universe and have survived through almost the entire span of galaxy growth and evolution.
Matt Taylor ... sets the scene: “Globular clusters and their constituent stars are keys to understanding the formation and evolution of galaxies. For decades, astronomers thought that the stars that made up a given globular cluster all shared the same ages and chemical compositions — but we now know that they are stranger and more complicated creatures.”
The elliptical galaxy Centaurus A (also known as NGC 5128) is the closest giant galaxy to the Milky Way and is suspected to harbour as many as 2000 globular clusters. Many of these globulars are brighter and more massive than the 150 or so orbiting the Milky Way.
Observational Evidence for a Dark Side to NGC 5128's Globular Cluster System - Matthew Taylor et al
- arXiv.org > astro-ph > arXiv:1503.04198 > 13 Mar 2015 (v1), 17 Mar 2015 (v2)
