photo and content credit to space.com
After its discovery in 2004, astronomers gave the asteroid Apophis a 2.4 percent chance of hitting the earth during its close flyby on April 13, 2029. If the 1,066-foot (325 meters) asteroid were to strike our planet, the blast could equal hundreds of megatons.
Fortunately, further analysis showed that Apophis will miss the Earth by 19,400 miles (31,300 kilometers) in 2029. Extrapolating further into the future, another approach in 2036 is an even bigger miss. Apophis has only a one in a million chance of hitting Earth on that pass.
An asteroid that approaches Earth closely is called a Near Earth Object, or NEO. Astronomers track these objects carefully to provide early warning if one is discovered to be on a collision course with Earth.