Scientific Information
Scientific Facts About Apophis
Asteroid 99942 Apophis is one of the most studied Near-Earth Objects ever discovered. Its historic close approach in 2029 will provide scientists with an unprecedented opportunity to observe a large asteroid at extremely close range.
How Close Will Apophis Get?
Apophis 2029
32,000 km
Closest approach distance
GEO Satellites
35,786 km
Geostationary orbit altitude
The Moon
384,400 km
Average Earth-Moon distance
On April 13, 2029, asteroid 99942 Apophis will make one of the closest known approaches of a large asteroid in recorded history.
Current calculations indicate that Apophis will pass approximately 32,000 km above Earth's surface.
For comparison, geostationary communication satellites orbit at approximately 35,786 km above Earth. This means Apophis will pass closer than many satellites used for television, communications and weather monitoring.
But... "That altitude is close enough that the Earth's gravity could deflect the asteroid onto a trajectory that brings it back to an Earth impact. Such impact trajectories require Apophis to pass the Earth at a precise altitude, known as a keyhole, in 2029 en route to a subsequent impact..." in 2036...
Source: Farnocchia et al. (2013), Near Earth Asteroids with measurable Yarkovsky effect | Local PDF copy
The Moon, by comparison, orbits Earth at an average distance of approximately 384,400 km.
In other words, Apophis will pass at only about 8% of the Earth-Moon distance.
Despite this extraordinary flyby, modern orbital calculations confirm that Apophis will safely miss Earth.
What is Apophis?
99942 Apophis is a near-Earth asteroid approximately 340 meters in diameter. It was discovered in 2004 and quickly attracted worldwide attention due to early impact probability calculations that were later ruled out through improved observations.
Why is the 2029 Flyby Important?
During the 2029 close approach, Apophis will become visible to the naked eye from parts of Europe, Africa and Asia. Scientists will be able to study how Earth gravity affects the asteroid orbit, rotation and surface structure.
Impact Risk
Current orbital calculations performed by NASA, ESA and JPL rule out an impact with Earth for at least the next century. Apophis is considered one of the best-known asteroid orbits in the Solar System.
Why were scientists once concerned about a future impact?
Before more precise observations became available, researchers studied whether Apophis could pass through a gravitational keyhole during the 2029 flyby.
Learn about gravitational keyholes →