Astronomers have identified that dwarf galaxies in the constellation Centaurus orbit in a flat plane rather than in random spheres defying the basic known standard model of cosmology. The finding also questions the existence of dark matter, which was believed to occupy 80 percent mass of the Universe.
Published in the journal Science, the new findings by a team of international researchers led by the University of Basel showed that large galaxies like the Milky Way are surrounded by smaller galaxies that orbit it like satellites.
According to the standard model of cosmology, the satellite galaxies randomly orbit the host galaxy in an unorderly manner due to the influence of dark matter which is yet to be discovered.
Earlier observations of Milky Way and the Andromeda galaxy had contradicted this model as astronomers discovered that satellite galaxies co-rotate the major host galaxies in disc-shaped plane patterns. Scientists who believed in the standard model advocated the findings as isolated cases. However, the recent finding suggests the widespread nature of the phenomenon.
Researchers led by Oliver Muller from the University of Basel's Department of Physics analyzed the movement of satellite galaxies around Centaurus A galaxy, which is located at a distance of 13 million light years from Earth.
The satellite galaxies were found at a plane which forms a perpendicular 90-degree angle with the parent galaxy. This orientation was, however, at a convenient angle for the studies from the Earth. The Doppler effect of the starlight from them has helped to determine the movement of objects.
The researchers found that 14 out of 16 satellite galaxies followed the same pattern of movement around the Centaurus in a common plane. However, the model simulation under dark matter influence should have resulted in different patterns and different planes for the majority of the satellite systems.
Oliver Muller said, "Coherent movement seems to be a universal phenomenon that demands new explanations." The astronomical observations challenge the simulations as the similar phenomenon has been observed in more galaxies.
The finding strengthens the theory that satellite galaxies are formed due to the collision of two large galaxies, out of debris formed by tidal forces.