Next-door neighbors.

Scientists have long suspected that the brilliant star Polaris, or the North Star, is part of a triple star system.

But until recently, researchers had only spotted one of Polaris's neighbors, which is clearly visible through a high-powered telescope.

The third star couldn't be seen because it is too faint and too close to Polaris, says Nancy Evans, an astronomer at Harvard-Smithsonian Center for Astrophysics. Researchers finally caught sight of the companion using images collected by the Hubble Space Telescope.