Although such gaseous material has previously been seen in rich clusters of galaxies, this is the first time such a hot medium has been found in a small group that is typical of most clusters in the universe. The existence of this gaseous envelope allows astronomers to measure the total mass of the system. The surprising result is that the total amount of material in the group is much larger than the sum of the mass of the hot gas and the stars in the galaxies. The NGC 2300 group is located about 150 million light-years from Earth in the direction of the northern circumpolar constellation Cepheus. The discovery appears to confirm previous suggestions of where most of the dark matter in the universe may be concentrated, namely in and around small groups of galaxies, according to astronomers.
Dark matter is believed to exist although it has never been seen because it emits no radiation.
It is presumed, therefore, that unknown, or dark, matter that would be attracted to the weak gravity of the fluctuation got the process started. Scientists also presume the existence of the invisible material because the speeds with which certain galaxies are moving, their rotational patterns and their shapes cannot be accounted for by the possible gravitational pull of observable matter close enough to influence them. Dark matter may, in fact, constitute up to 95 percent of the mass of the universe. This means that eventually the expansion of the universe, which is being slowed by the pull of gravity, would come to a halt or nearly so. Md. They show that the small group of galaxies is immersed in a huge cloud of hot gas, about 1.3 million light- years in diameter, he explained.