In 2029 asteroid Apophis will pass closer than some of our satellites

On April 13, 2029, a stony asteroid roughly the size of a cruise ship will sweep past Earth at a distance that once seemed unthinkable for an object its size. The rock, formally cataloged as 99942 Apophis, will not strike the planet, but it will thread the crowded zone where communications and weather satellites orbit. For sky watchers across parts of Europe, Africa and western Asia, the flyby will be visible to the naked eye as a moving point of light, an event that happens perhaps once every several thousand years for an asteroid this large.

The approach has been anticipated for the better part of two decades, ever since the asteroid was first spotted and its orbit worked out. That long lead time has turned what began as a source of alarm into one of the most carefully planned observing campaigns in the history of planetary science, with spacecraft already dispatched to meet the object as it arrives.

How close is close

When Apophis reaches its nearest point, it will pass about 20,000 miles (32,000 kilometers) above Earth’s surface, according to NASA’s Jet Propulsion Laboratory. That figure is worth sitting with. The ring of geostationary satellites that relay television, weather imagery and some communications traffic sits at an altitude of roughly 22,236 miles (about 36,000 kilometers). The asteroid will therefore dip inside that ring, passing beneath a class of spacecraft that people rely on every day without knowing they are there.

The odds of a collision with any operational satellite are extremely small. Space is vast even in the busy geostationary belt, and the satellites there are spread thinly around a circle more than 165,000 miles in circumference. Mission planners nonetheless treat the encounter as a case study, because it is the first time in the modern era that an asteroid of this scale will cross that particular altitude. Tracking the object’s path with precision matters both for reassurance and for the science the flyby makes possible.

What Apophis actually is

Apophis is a near-Earth asteroid with a mean diameter of about 1,115 feet (340 meters) and a longest axis of at least 1,480 feet (450 meters), making it comparable in length to several city blocks laid end to end. It belongs to the population of stony asteroids that share the inner solar system with Earth, and its orbit carries it across the planet’s own path. Discovered in 2004, the object was named after the ancient Egyptian serpent of chaos, a fitting nickname given the alarm that surrounded early forecasts of its trajectory, as summarized in the public record of the asteroid’s tracking history.

For a brief period after its discovery, calculations suggested a small but non-trivial chance that Apophis could strike Earth in 2029. Additional observations progressively narrowed the possibilities, and refined orbital measurements have since ruled out an impact in 2029, in 2036 and for at least the following century. The asteroid has effectively moved off the list of near-term threats, which frees scientists to treat the 2029 pass as an opportunity rather than an emergency.

A natural experiment in Earth’s grip

The most compelling reason to study the flyby has less to do with danger and more to do with physics. When a rubble-pile asteroid passes this near a planet, Earth’s gravity tugs unevenly on its near and far sides, a tidal stress that can nudge boulders, alter the object’s spin and possibly trigger small landslides across its surface. Watching those changes unfold gives researchers a rare window into how loosely bound asteroids hold together, information that feeds directly into planetary-defense planning for objects that might one day pose a real risk.

Because the pass is predictable years in advance, agencies have time to position instruments to capture it. NASA’s science division has redirected the spacecraft that collected a sample from asteroid Bennu, renaming the mission OSIRIS-APEX and sending it to rendezvous with Apophis and study it in the weeks after the close approach. The European Space Agency has planned a companion effort, a mission designed to reach the asteroid before the flyby and observe it in real time as Earth’s gravity does its work. Together those missions aim to measure the object’s shape, composition and internal structure with a level of detail that ground-based telescopes cannot match.

What people on the ground will see

For the public, the flyby will register as a modest but genuine spectacle. Under clear skies in the Eastern Hemisphere, Apophis is expected to appear as a starlike dot drifting steadily against the fixed background of the constellations, bright enough to follow without a telescope or even binoculars. Its motion will be perceptible over minutes, a reminder that the objects astronomers usually describe in charts and coordinates are real bodies moving through nearby space.

The encounter also carries a broader lesson about the state of planetary defense. A generation ago, an asteroid of this size arriving on such a close trajectory would have been detected late, if at all, and would have offered little chance for study. The fact that scientists identified Apophis decades ahead, calculated its path, cleared it of impact risk and organized spacecraft to greet it reflects how far the field of asteroid tracking has advanced. Surveys now scan the sky for objects that cross Earth’s orbit, and each new detection sharpens the catalog of what shares the neighborhood.

Apophis will continue on its way after 2029, its orbit slightly reshaped by the close pass but no longer a candidate for collision. The data gathered during those days is expected to inform how researchers model every large near-Earth asteroid that follows. In that sense the flyby is less a brush with catastrophe than a scheduled appointment, one that the scientific community has spent years preparing to keep.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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