The Milky Way is a massive galaxy that attracts smaller “satellite galaxies” to orbit around it. These satellite galaxies, which contain only a few billion stars, have been captured by the Milky Way’s gravitational pull over billions of years. While some prominent satellite galaxies like the Large Magellanic Cloud and the Small Magellanic Cloud are visible from the Southern Hemisphere without a telescope, most satellite galaxies are too small and dim to be seen without powerful telescopes.
Scientists use advanced instruments with wide fields of view to discover these dwarf galaxies, with the ability to detect even ultra-faint dwarfs that have just a few hundred thousand stars. To confirm if a nearby dwarf galaxy is a Milky Way satellite, scientists analyze the light it emits through spectroscopy to determine its motion and direction.
A recent census estimated that there are about 60 satellites orbiting the Milky Way within a distance of 1.4 million light-years. However, the exact number of satellite galaxies is challenging to determine because not all proposed satellites have been spectroscopically confirmed to be orbiting the Milky Way. New satellite candidates are still being discovered, making the count a continuously changing number.
Over the years, advancements in technology have significantly increased the number of known satellite galaxies orbiting the Milky Way. Surveys like the Sloan Digital Sky Survey and the Dark Energy Survey have revealed dozens more satellites, with the upcoming Vera C. Rubin Observatory expected to find hundreds more. However, the Milky Way’s gravitational pull also poses a threat to these satellite galaxies, eventually consuming them over billions of years.
Dwarf galaxies like Gaia Enceladus have already been shredded and devoured by the Milky Way, with their stars now part of the Milky Way’s halo. In the far future, the current visible satellite galaxies will likely meet the same fate, merging with the Milky Way to create an even bigger central galaxy.
As technology continues to advance, scientists will likely discover more satellite galaxies orbiting the Milky Way, shedding light on the complex interactions between galaxies in our cosmic neighborhood. With new discoveries on the horizon, the study of satellite galaxies offers valuable insights into the evolution and fate of galaxies in the universe.
