Alinda asteroid

The Alinda asteroids are a group of asteroids with a mean orbital radius of 2.5 AU and an orbital eccentricity approximately between .4 and .65. These objects are held in this region by the 1:3 orbital resonance with Jupiter. An object in this resonace has its orbital eccentricty steadily increased by gravitational interactions with Jupiter until it eventually has a close encounter with an inner planet that breaks the resonance. Some Alindas, such as 4179 Toutatis, have perihelia very close to Earth's orbit resulting in a series of close encounters at four-year intervals.