On April 13, 2029, a near-Earth asteroid roughly the size of a large skyscraper will sweep past the planet closer than many of the satellites in orbit above it. The object is called 99942 Apophis, and its approach will be one of the closest passes by an asteroid of its size ever predicted — close enough that people across parts of the Eastern Hemisphere will be able to watch it cross the night sky without a telescope. Despite the drama of the encounter, astronomers now say there is no chance the asteroid will strike Earth.
Apophis has a long and unusually public history as a hazard. When it was first spotted, it briefly ranked among the most threatening objects ever cataloged, and only years of careful tracking downgraded it from a genuine danger to a once-in-a-generation spectacle. Its 2029 flyby is now regarded less as a threat than as an extraordinary scientific opportunity.
How close Apophis will come
The numbers are what make the encounter remarkable. According to NASA, Apophis will pass about 20,000 miles — roughly 32,000 kilometres — from Earth’s surface. That is nearer than the ring of geosynchronous satellites, which orbit at an altitude of about 22,236 miles, and it is roughly a tenth of the distance to the Moon. An object several hundred metres across coming that close is a genuinely rare event; typically, only much smaller rocks approach at such range, and they are usually too faint to notice.
Because of that proximity, the asteroid will be visible to the naked eye as a moving point of light for observers in parts of Europe, Africa and Asia, tracing a path across the sky over the course of the evening. It will require no special equipment to see, an experience that is essentially unheard of for an asteroid of this scale.
A rock the size of a skyscraper
Apophis is an elongated, peanut-shaped body estimated at somewhere between roughly 340 and 450 metres across, depending on how it is measured — dimensions comparable to a very tall building laid on its side. Its shape and rough size have been refined using ground-based radar, including observations made in 2021 when radio antennas at NASA’s Goldstone complex and the Green Bank Telescope imaged the asteroid from about 10.6 million miles away. It is classified as a stony, “S-type” asteroid, meaning it is composed largely of silicate rock and nickel-iron rather than loose rubble or ice.
From threat to safe flyby
The asteroid was discovered on June 19, 2004, by astronomers Roy Tucker, David Tholen and Fabrizio Bernardi observing from Kitt Peak National Observatory in Arizona. Early orbital calculations suggested a small but real chance that Apophis could hit Earth in 2029 or on a later return, and for a time it climbed to the top of impact-risk lists. As more observations refined its trajectory, the odds of a 2029 impact were eliminated, and lingering concern about a possible 2036 collision was ruled out as well.
After further tracking with optical telescopes and radar, mission scientists concluded that the orbit of Apophis poses no risk of striking Earth for at least a century. The European Space Agency’s planetary-defense specialists reached the same conclusion, and the object has since been removed from the risk registers that flag potentially hazardous encounters. What remains is a predictable, well-understood flyby rather than a looming catastrophe.
A once-in-a-generation science target
The proximity that once made Apophis alarming now makes it invaluable. Earth’s gravity will tug on the asteroid as it passes, potentially altering its spin and even reshaping its surface in subtle ways, and researchers want to watch that happen in real time. The European Space Agency and other agencies have described the 2029 approach as a natural experiment that could reveal how a rubble-strewn stony asteroid responds to a planet’s gravitational pull — knowledge directly relevant to any future effort to deflect a genuinely dangerous object.
Spacecraft are being marshaled to meet it. NASA has redirected a probe, renamed OSIRIS-APEX after its earlier mission to the asteroid Bennu, to rendezvous with Apophis around its closest approach and study it up close, using the spacecraft’s thrusters to disturb surface material and expose what lies just beneath. Ground-based telescopes worldwide will observe the flyby simultaneously, making it one of the most closely watched asteroid encounters in history.
Why planetary defense pays attention
Even with the impact threat retired, Apophis remains central to the field of planetary defense. Government scientists study close approaches like this one to understand the cascade of consequences a real impact could set off, and to test the tracking and prediction tools that would give the world warning. The United States Geological Survey has treated the 2029 approach as a case study in the hazards asteroids can pose and the value of preparing for them in advance.
The encounter also offers a chance to rehearse international coordination, as observatories, space agencies and researchers on several continents plan to share tracking data and observations across the flyby. Lessons drawn from studying how Apophis behaves — how it tumbles, how sunlight and gravity nudge its path over time — feed directly into models used to assess other objects still being discovered.
For the general public, though, the takeaway is simpler and more reassuring. A skyscraper-sized asteroid really will pass startlingly close to Earth in the spring of 2029, close enough to see with the unaided eye — and thanks to decades of patient observation, scientists can say with confidence that it will pass by harmlessly, leaving behind data rather than damage.
This article was produced with AI assistance and reviewed by Morning Overview editors.
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