Dark globular cluster
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Dark globular cluster is a proposed type of globular star clusters that has an unusually high mass for the number of stars within it. Proposed in 2015 on the basis of observational data, dark globular clusters are believed to be populated by objects with significant
dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not ab ...
components, such as central massive
black holes A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can def ...
.


Observational data

The observational data for dark globular clusters comes from the
Very Large Telescope The Very Large Telescope (VLT) is a telescope facility operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each with a primary mirror 8.2 m across, ...
(VLT) in Chile which observed the vicinity of the galaxy
Centaurus A Centaurus A (also known as NGC 5128 or Caldwell 77) is a galaxy in the constellation of Centaurus. It was discovered in 1826 by Scottish astronomer James Dunlop from his home in Parramatta, in New South Wales, Australia. There is considerable d ...
. Many of the globular clusters inside that galaxy are brighter and more massive than those orbiting the
Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...
and a sample of 125 globular clusters around Centaurus A was studied using the VLT's FLAMES instrument. While globular clusters are normally considered to be almost devoid of dark matter, the study of the dynamical properties of sampled clusters suggested the presence of exotically concentrated dark matter. The existence of dark globular clusters would suggest that their formation and evolution are markedly different from other globular clusters in Centaurus A and the
Local Group The Local Group is the galaxy group that includes the Milky Way. It has a total diameter of roughly , and a total mass of the order of . It consists of two collections of galaxies in a "dumbbell" shape: the Milky Way and its satellites form ...
.


See also


References

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