https://www.sciencedaily.com/releases/2014/09/140908204603.htm According to this article dark matter is warm, and provides a mechanism for showing the lack of satellite around the milky way. Date: September 8, 2014 Source: Royal Astronomical Society (RAS) Summary: Scientists believe they have found a way to explain why there are not as many galaxies orbiting the Milky Way as expected. Computer simulations of the formation of our galaxy suggest that there should be many more small galaxies around the Milky Way than are observed through telescopes. This has thrown doubt on the generally accepted theory of cold dark matter, an invisible and mysterious substance that scientists predict should allow for more galaxy formation around the Milky Way than is seen. Now cosmologists think they have found a potential solution to the problem.