The astronomers analyzed spectra from observations they made with the Anglo-Australian Telescope and the Cerro Tololo Interamerican Observatory. Ibata, Gilmore and Irwin made the original discovery in 1994. It is important to study Sagittarius in the overall quest to learn how galaxies form and evolve, Wyse said. Astronomers propose that such small companion galaxies might have merged to make the larger galaxies like the Milky Way. Sagittarius also gives astronomers an opportunity to study the dark matter of another galaxy up close.
Scientists hope to clarify what the nature of the dark matter is.
According to theories and observations, the universe contains more matter than is directly observed using current technology. Astronomers think that at least 90 percent of the mass in the universe is yet to be observed directly. By comparing the number of stars and the luminosity of Sagittarius, astronomers will be able to learn what kinds of dark matter prevail in that galaxy. In the near future, astronomers hope to learn whether other companion galaxies also are invading the Milky Way. Because the Sagittarius discovery was made by chance, it is possible that such galaxies have gone undetected.