What is Apophis?

Apophis is a near-Earth asteroid, meaning its orbit around the Sun brings it within 1.3 times the distance between the Sun and Earth. Its full name is Apophis 99942. After Apophis was discovered in 2004, the asteroid was given a 2.7% chance of hitting Earth in 2029, causing a great deal of media attention. It also for a time had a small chance of hitting Earth in 2036. Additional observations have shown it will not hit Earth in 2029 or in 2036.

Nevertheless, in 2029 Apophis will come closer to Earth than our geostationary communications satellites, likely sparking a great deal of public interest.

What does Apophis mean?

In Egyptian mythology, Apophis was a serpent and the enemy of Ra, the sun god. Every night Apophis sought to bring eternal darkness on the world before being defeated by Ra at sunrise.

Who discovered Apophis?

Apophis was discovered on 19 June 2004, by Roy Tucker, David Tholen, and Fabrizio Bernardi at the Kitt Peak National Observatory in Arizona. Tucker was a 2002 grant recipient from our shoemaker near earth object program, which funds advanced amateur astronomers who find, track and characterize near-Earth objects.

How big is Apophis?

Like most asteroids, Apophis is too small for us to figure out its exact shape and size from Earth. Radar images have shown it measures 450 meters (1500 feet) across its longest axis, equivalent to about 5 football fields and taller than the Empire State Building in New York City. It is approximately 170 meters on its shortest axis. It is likely egg-shaped or even dual-lobed like Arrokoth, the small world NASA’s New Horizons spacecraft flew past in 2019.

Will Apophis hit Earth?

Not anytime soon. It definitely will miss Earth in 2029 and 2036, and radar observation of Apophis during the asteroid’s flyby in March 2021 ruled out an impact for at least the next 100 years.

Why did the probability of Apophis impact in 2029 go up before it went down to zero?

Soon after its discovery, more observations of Apophis refined the asteroid’s trajectory, and the range of trajectories still included Earth. More observations refined its path around the Sun and excluded Earth, bringing the probability of a 2029 impact down to zero.

What would happen if Apophis hit Earth?

Apophis would cause widespread destruction up to several hundred of kilometers from its impact site. The energy released would be equal more than 1,000 megatons of TNT, or tens to hundreds of nuclear weapons.

How close will Apophis come to Earth in 2029?

On 13 April 2029 Apophis will pass as close as 30,600 kilometers (19,000 miles) above the Earth. If you’re superstitious, that’s on a Friday the 13th.

How close will Apophis come to Earth in 2036?

On 30 March 2036 Apophis will pass Earth at a much further distance: 8.4 million kilometers (5.2 million miles). That’s more than 20 times the distance between the Earth and Moon.

Will we be able to see Apophis?

During the 2029 pass Apophis will be visible from Europe, Africa, and western Asia looking like a somewhat bright star (magnitude 3.1) moving rapidly across the sky. It will be much too far away to be visible without telescopes in 2036.

Will Apophis hit our geostationary communications satellites?

No. Apophis will pass closer to Earth than some of our geostationary satellites, but its path will be inclined away from the equator and not carry it through the region these satellites occupy.

Could we stop an asteroid like Apophis?

With enough warning time before impact, meaning many years, we could change the orbit of an asteroid the size of Apophis enough to cause it to miss the Earth, but this would require a coordinated global effort.

Is anyone planning a mission to Apophis?

NASA’s OSIRIS-APEX mission will study the asteroid for 18 months starting in April 2029, just before it makes its close approach to Earth. OSIRIS-APEX is the repurposed OSIRIS-REx spacecraft that returned a sample of asteroid Bennu to Earth in September 2023.

OSIRIS-APEX will study how Earth’s gravity changes Apophis’ rotation rate and surface properties, which could help us understand what lies beneath the asteroid’s surface. The mission will give us new insight into asteroids similar to Apophis, including how we might deflect one on course to hit Earth.