Apophis, officially designated 99942 Apophis, is a near-Earth asteroid that has captured global attention since its discovery in 2004. Initially estimated to have a 2.7% chance of impacting Earth in 2029, this asteroid sparked widespread media coverage and public interest. Fortunately, further observations confirmed that it will not collide with our planet, including during its close approaches in 2029 and 2036.
Measuring approximately 450 metres across, Apophis will pass as close as 30,600 kilometres (19,000 miles) from Earth on April 13, 2029, making it one of the closest encounters with a significant asteroid in recent history. As scientists prepare to study this intriguing celestial body, the upcoming flybys present valuable opportunities for research and public engagement.
What is Apophis?
Apophis, formally known as 99942 Apophis, is a near-Earth asteroid with an orbit that brings it within 1.3 times the distance between the Earth and the Sun. Since its discovery in 2004, it has captured significant media attention, particularly when it was initially estimated to have a 2.7% chance of impacting Earth in 2029. There was also a brief period during which it was thought to pose a risk in 2036. However, further observations have confirmed that Apophis will not collide with Earth in either of these years.
Upcoming close approaches by Apophis
While Apophis won’t collide with Earth, it will come very close on April 13, 2029. On that day, it will pass just 30,600 kilometres (19,000 miles) away from Earth, closer than some of our geostationary satellites. This close encounter is expected to spark public interest, and organisations like the Planetary Society are recommending ways to educate the public about the event. On March 30, 2036, Apophis will be much farther away, passing Earth at a distance of 8.4 million kilometres (5.2 million miles), which is more than 20 times the distance to the Moon.
Origin and discovery of Apophis
The name “Apophis” is derived from Egyptian mythology, where Apophis represents a serpent that is the enemy of Ra, the sun god. Each night, Apophis attempted to engulf the world in darkness, only to be defeated by Ra at dawn.
Apophis was discovered on June 19, 2004, by astronomers Roy Tucker, David Tholen, and Fabrizio Bernardi at the Kitt Peak National Observatory in Arizona. Tucker had previously received a grant from the Shoemaker Near Earth Object Grant Program, which supports amateur astronomers in their efforts to find, track, and characterise near-Earth objects.
Size and structure of Apophis
Determining the exact size and shape of Apophis from Earth is challenging due to its small size. However, radar imaging has revealed that Apophis measures approximately 450 metres (1,500 feet) across its longest axis—comparable to five football fields and taller than the Empire State Building.
Its shortest axis measures about 170 metres. The asteroid is likely to be egg-shaped or possibly dual-lobed, resembling Arrokoth, a small celestial body that NASA’s New Horizons spacecraft encountered in 2019.
What will happen if Apophis hits Earth?
Currently, Apophis is not expected to hit Earth anytime soon. It will definitely miss Earth in 2029 and 2036, and observations made in March 2021 ruled out any risk of impact for at least the next 100 years. Initially, the chance of a 2029 impact was higher because early observations had not yet refined its trajectory. As more data became available, scientists were able to rule out the possibility of an impact.
If Apophis were to collide with Earth, it would cause significant destruction, with effects felt hundreds of kilometres from the impact site. The energy released would be equivalent to over 1,000 megatons of TNT, similar to multiple nuclear explosions. In comparison, the asteroid that caused the extinction of the dinosaurs was much larger, at least 10 to 15 kilometres wide.
Will Apophis hit our satellites?
Apophis will not collide with our geostationary communications satellites. While it will pass closer than some of these satellites, its trajectory is inclined away from the equator, ensuring it does not enter the region occupied by these vital communications systems.
Will we be able to see Apophis?
Yes, during its 2029 close approach, Apophis will be visible from Europe, Africa, and western Asia, appearing as a bright star moving across the sky. In 2036, it will be too far away to see without a telescope.
How do astronomers track asteroids?
Astronomers monitor asteroids like Apophis through a combination of follow-up observations and tracking efforts. These observations are gathered from both professional astronomers and skilled amateurs, then submitted to the Minor Planet Center. Teams at NASA’s Jet Propulsion Laboratory and the NEODyS program in Italy compute the orbits of asteroids based on this data. The accuracy of these predictions is determined by the quality and quantity of observations.
In some cases, radar is employed to obtain precise distance measurements, further refining orbital predictions. Additionally, spacecraft missions to near-Earth asteroids provide even more accurate orbital data.
Future missions to Apophis
NASA’s OSIRIS-APEX mission will study Apophis for 18 months starting in April 2029, just before its close encounter with Earth. This mission uses the OSIRIS-REx spacecraft, which recently returned samples from the asteroid Bennu.
OSIRIS-APEX will investigate how Earth’s gravity affects Apophis’ rotation and surface properties. This study could provide valuable insights about the asteroid and help scientists learn how to deflect similar objects that might threaten Earth in the future. As we approach the close encounters with Apophis, ongoing research and public education will be important for understanding this fascinating asteroid.
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