Image courtesy of NASA via spacetoday
A big conundrum in astronomy and cosmology over the last ten years has been the ‘Missing Dwarf Galaxy’ Problem. Dwarf Galaxies are much smaller than normal galaxies and though this makes them fainter and harder to find, astronomers have still been finding far fewer than predicted. The prediction comes from the ‘Cold Dark Matter’ model. Dark matter, which is thought to make up around 22% of all substance in the universe compared to about 2-5% of the matter we can see, forms in distinct ‘halos’, in which real galaxies form. (The remaining 74% of energy density is the mysterious dark energy, responsible for the expansion of the universe.)
By studying the distribution of these dark matter halos, astronomers predicted that a large galaxy such as our own Milky Way should have a hundred or so smaller dwarf satellites. The problem is, until very recently only a handful had been seen. A lot of these could have no visible stars and it was difficult to see a way to detect them. Until now. Two astronomers using the W. M. Keck Observatory in Hawaii think they may have found a load more, possibly solving one of the biggest questions in our study of the stars.