Astronomers find dark globular clusters
Centaurus A – a giant galaxy, 5th brightest galaxy in Earth’s sky beyond our Milky Way – continues to surprise us. Now astronomers observing with the European Southern Observatory’s Very Large Telescope in Chile say they’ve discovered a new class of globular star clusters orbiting the center of Centaurus A. They’re calling them dark globular clusters. These mysterious objects look similar to normal clusters, but have much more mass than expected. The astronomers speculate the mysterious clusters might harbor dark matter, or contain massive black holes. They announced their work today (May 13, 2015).
The elliptical galaxy Centaurus A (also known as NGC 5128) is the closest giant galaxy to the Milky Way. It’s thought to have as many as 2,000 globular clusters. Many of these globulars are brighter and more massive than the 150 or so globulars orbiting our Milky Way.
Astronomer Matt Taylor of the Pontificia Universidad Catolica de Chile in Santiago is lead author of the new study. He and his team made detailed studies of 125 globular star clusters orbiting the center of Centaurus A.
They used these observations to deduce the mass of the clusters, by studying the motions of the clusters’ stars. This orbital information depends on the strength of the gravitational field of each cluster and thereby can be used to deduce each cluster’s mass.
http://earthsky.org/space/astronomers-discover-dark-globular-clusters
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