Lockman and his colleagues used the Green Bank Telescope in West Virginia to compare the Smith Cloud with others near the galaxy and seven massive ones that sit between the Andromeda and Triangulum galaxies. Smith’s Cloud is more similar to the ones that sit far-off, which suggests that the cloud originated billions of years ago in a distant region of space. Its trajectory indicates that the cloud has collided with the Milky Way before. With each interaction, it brings fresh, nongalactic material to the Milky Way, Lockman said February 15 at the annual meeting of the American Association for the Advancement of Science.
The results reinforce the idea that the space between galaxies is not empty. It’s messy, filled with “funny little clouds that seem to have a life of their own,” Lockman said.