Explained: What is 99942 Apophis? Why are scientists excited?

On April 13, 2029, a near-Earth asteroid will cruise by Earth, about 31,000 km above the surface. Although the flyby is expected to be harmless, the international asteroid research community is excited.

Artist’s representation of the Apophis asteroid at closest approach. The dots denote man-made satellites orbiting Earth. (NASA JPL)

On April 13, 2029, a near-Earth asteroid will cruise by Earth, about 31,000 km above the surface. Although the flyby is expected to be harmless, the international asteroid research community is excited, with scientists drawing up plans 10 years in advance on how they will observe it with optical and radar telescopes, and discussing what they hope to learn.

The asteroid, called 99942 Apophis, is 340 m wide. At one point, it will travel more than the width of the full Moon within a minute and it will get as bright as the stars in the Little Dipper, according to NASA’s Jet Propulsion Laboratory.

It is rare for an asteroid this size to pass by Earth so close. Although scientists have spotted small asteroids, on the order of 5-10 metres, flying by Earth at a similar distance, asteroids the size of Apophis are far fewer in number and so do not pass this close to Earth as often.

Story continues below this ad

Among potential lessons from Apophis, scientists are hoping they can use its flyby to learn about an asteroid’s interior.

Apophis is one of about 2,000 currently known Potentially Hazardous Asteroids, and scientists also hope their observations might help gain important scientific knowledge that could one day be used for planetary defence.