On January 26, the largest asteroid until 2027 will make a quick flyby of the Earth-moon system. A mountain-size space rock will sail past Earth on Monday, offering stargazers a close look at an interplanetary pinball. Luckily, NASA says there is no risk of collision, but it will be a rare astronomically close encounter that backyard telescope owners can watch. The large asteroid, called 2004 BL86, measures about a third of a mile (half a kilometer) across. It will make its closest approach to Earth on January 26, coming within only 745,000 miles (1.2 million kilometers) from our planet—about three times the distance separating the Earth and the moon. While there have been many asteroids that have barnstormed Earth much closer, this will be the largest one to come that close until 2027, when a slightly smaller asteroid, 1999 AN10, may come closer to Earth than the moon. What makes Monday's flyby most unusual is that it will be bright enough for small backyard telescopes to glimpse as it sweeps past our planet. Also making it of interest to astronomers is the fact that it belongs to a group of 551 known near-Earth asteroids that have the potential for impact sometime in the future. Luckily, 2004 BL86 doesn't seem to have our number just yet. "Monday, January 26, will be the closest asteroid 2004 BL86 will get to Earth for at least the next 200 years," said Don Yeomans, manager of NASA's Near Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, California, in a statement. More via Nat Geo.