The closest any celestial object of that magnitude will have come near Earth in recent history will be an asteroid approximately the width of the Empire State Building, which astronomers say will rip through space within 20,000 miles (32,200 km) of Earth in about 5-1/2 years.
When it does, a NASA spacecraft that was launched in 2016 should be able to offer a thorough analysis of this unusual close approach.
The mission, directed by University of Arizona scientists, is expected to yield insights into planetary formation and knowledge that could inform efforts to build a defense system against possible doomsday asteroid collisions with Earth.
At the time of its 2004 discovery, the asteroid Apophis, named for a demon serpent embodying evil and chaos in ancient Egyptian mythology, appeared to pose a dire impact threat to Earth, with scientists forecasting a potential collision in 2029. Refined observations have since ruled out any impact risk for at least another century.