Near-Earth object observation log · Est. 2004
On a Friday evening in April 2029, an asteroid the size of a skyscraper will slide between Earth and its own television satellites — the closest pass by an object this large that astronomers have ever been able to predict. It will miss. And an estimated two billion people will be able to watch it cross the sky with their naked eyes.
Friday · 13 April 2029 · 21:46 UTC
Apophis is moving. Since you opened this page it has covered 0 km along its orbit — about 31 kilometres every second.
This is the encounter geometry, computed from the flyby's real orbital energy and drawn to scale. Drag the slider to move Apophis along its hyperbolic path. Earth's gravity bends the asteroid's course by 28 degrees and flings it onto a new orbit — the pass permanently changes it.
Two-body geometry from the encounter's orbital energy (perigee 38,012 km geocentric, 7.42 km/s). The real trajectory, perturbed by the Moon and the Sun, is known to within about ±3 km.
Space is deep, so this ruler is logarithmic — every gridline is ten times farther than the last. Hover or tap the markers.
Apophis threads the needle at 31,600 km — above the GPS constellation, but 4,200 km inside the geostationary belt where broadcast and weather satellites live. No asteroid this large has ever been seen doing that.
Radar shows Apophis is two lobes fused into one elongated body about 450 metres end to end — stood upright, it would clear the Empire State Building's antenna.
Roy Tucker, David Tholen and Fabrizio Bernardi catch a faint dot from the Kitt Peak National Observatory, Arizona. It gets the provisional tag 2004 MN4.
Orbit solutions briefly give a 2.7% chance of impact on 13 April 2029. Apophis reaches level 4 on the Torino hazard scale — the highest rating any asteroid has ever held, before or since. Further observations soon rule the impact out.
A distant flyby lets Goldstone radar refine the orbit. The 2029 encounter is confirmed as a spectacular near miss.
A final radar campaign nails the orbit down to metres. Apophis is removed from the Sentry Risk Table: no impact risk for at least 100 years, including the once-feared 2036 and 2068 passes.
ESA's ministerial council fully funds Ramses, the mission that will escort Apophis through the flyby, within a record €955 million space-safety budget.
The ESA–JAXA spacecraft departs, timed to reach the asteroid two months before the encounter.
Apophis crosses the evening sky over Europe, Africa and western Asia at magnitude 3.1, bright enough for the naked eye, drifting visibly against the stars. Earth's tides may trigger landslides on it and retune its spin.
NASA's Bennu veteran arrives just after the flyby and settles into orbit for an 18-month survey of a freshly Earth-shaken asteroid.
The next pass is a comfortable 46 million km away. The serpent, thoroughly measured, keeps circling the Sun.
A flyby this close happens roughly once every 7,500 years for an asteroid this size. Space agencies are treating it as a free planetary-defence experiment — Earth's gravity does the shaking, the probes take the measurements.
The Rapid Apophis Mission for Space Safety rendezvouses with the asteroid in February 2029 and holds station through the encounter — watching in real time as Earth's tidal forces twist the asteroid's spin and shift its surface.
Funded in full at ESA's November 2025 ministerial; built by OHB under an €81M spacecraft contract, with JAXA contributing hardware and a lander concept.
The spacecraft that brought home samples of asteroid Bennu was rerouted to Apophis. It arrives shortly after closest approach and spends 18 months mapping the asteroid — including firing thrusters at the surface to peek beneath it.
Slated for cancellation in 2025 budget cuts, it was saved by a last-minute congressional allocation. The chase continues.
No. After the 2021 radar campaign, an impact was ruled out for at least the next 100 years and Apophis was removed from every risk list. The 2029 miss distance is known to within a few kilometres — for a gap of 31,600 km, that is certainty by astronomical standards.
If you are in Europe, Africa or western Asia on the evening of 13 April 2029 — yes, with your naked eyes. Apophis will brighten to magnitude 3.1, about as bright as the stars of the Little Dipper, and it will visibly crawl across the sky over the course of the evening. Everyone else needs a livestream or binoculars and patience.
An asteroid this large passes this close roughly once every 7,500 years. Ours happens to arrive in the age of radar, spaceflight and countdown websites. No human has ever watched a 300-metre-plus asteroid at this distance — and had years of warning that it was coming, and that it would miss.
Earth will not break it — Apophis stays well outside the Roche limit. But tidal forces are expected to alter its tumbling spin and may trigger landslides and expose fresh, unweathered rock. The pass also bends its path by about 28°, moving it from an Aten-class orbit to an Apollo-class one. Ramses and OSIRIS-APEX exist to measure exactly this before-and-after.
An impact by a 340-metre stony asteroid would release on the order of a thousand megatons — devastation across a region the size of a country, but nothing like the dinosaur-ending event (that asteroid was ~30 times wider). This is precisely why planetary-defence missions rehearse on safe passes like this one.
Apophis is the Greek name of Apep, the ancient Egyptian serpent of chaos and darkness who tried to swallow the sun god Ra every night — and was defeated every dawn. Discoverers Tholen and Tucker were also fans of the TV series Stargate SG-1, whose main villain borrows the same name. Both stories end the same way: the serpent doesn't win.