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NGC 3201 - a poorly known globular cluster with a black hole in its central region

Description of object:

NGC 3201 is a bright, large and relatively unknown globular cluster in the constellation Vela (Sail of the Ship). It has a brightness of almost 7 magnitudes and an apparent diameter of 18 arcminutes. The distance to the solar system is about 16 000 light-years and thus has a physical diameter of 80 light-years. The age is estimated to be 10 billion years and the total mass is about 250 000 solar masses. It is classified as type X.

In our Milky Way there are about 150 known globular clusters, but there are probably many more. They form a spherical shell around the center of our galaxy to which they are gravitationally bound.

NGC 3201 shows some unusual features compared to other globular clusters. First, it shows an "inhomogeneous" distribution of stars, with red, cooler stars concentrated towards the center and blue, hotter stars that are further distributed throughout the cluster. On the other hand, at 240 km/s (relative to the center of the Galaxy), it moves much faster than many other globular clusters, but still slow enough to be gravitationally bound to the Galaxy. From the observations it could be concluded that the star orbits a dark object which remains invisible.

From the data, astronomers determined that the visible star has 0.8 times the mass of our Sun, while the mass of its mysterious companion is 4.4 times the mass of our Sun - so it is almost certainly a black hole. More information about the discovery can be obtained directly from ESO at this URL.

NGC 3201 was discovered on 1 May 1826 by the Scottish astronomer James Dunlop, who was observing from New South Wales in Australia.

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