An asteroid between 130 and 300 feet wide has a slight chance of hitting Earth in 2032 — but the precise odds have been a moving target since the space rock was first detected nearly two months ago.

Richard Binzel has been watching the skies for hazardous asteroids for more than 50 years. In 1995, he proposed the Near-Earth Object Hazard Index, later renamed the Torino scale, which rates ...