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Some new information from NASA's Jet Propulsion Laboratory shows that the link between galaxy clusters, ie thousands of galaxies, along with elusive dark matter, is extremely complex.

Even though it is known that galaxy clusters lay in areas in which dark matter is dense, the new study now shows that density of dark matter has a relationship with the internal structure of galaxy clusters.

"Galaxy clusters are like the large cities of our universe," Hironao Miyatake at NASA's Jet Propulsion Laboratory, said in a press release."In the same way, that you can look at the lights of a city at night from a plane and infer its size, these clusters give us a sense of the distribution of the dark matter that we can't see."

The team studied about 9,000 galaxy clusters from the Sloan Digital Sky Survey DR8 galaxy catalogue. They made lists of two cluster groups. One group had spread out galaxy distributions and in another, they were tightly packed.

The team discovered that the tightly packed galaxies had fewer neighboring clusters, so, the surrounding dark matter determines the density of the galaxy cluster.

"This difference is a result of the different dark-matter environments in which the groups of clusters formed. Our results indicate that the connection between a galaxy cluster and surrounding dark matter is not characterized solely by cluster mass, but also its formation history," Miyatake said.

The results show the way to the leading theory on the origins of our universe. It hypothesizes that the galaxy clusters are due to changes in the early universe's matter density. They happened to the cosmic inflation after the Big Bang.

"The connection between the internal structure of galaxy clusters and the distribution of surrounding dark matter is a consequence of the nature of the initial density fluctuations established before the universe was even one second old," Miyatake said.

The findings were published in the Jan. 25,2016 issue of Physical Review Letters.