Closest Asteroid
Approaches Ever

Confirmed passes versus estimated prehistoric approaches

This list covers only approaches with confirmed orbital solutions, meaning astronomers have enough observations to calculate a reliable orbit and reconstruct when the object was closest to Earth. Prehistoric impacts are not included, and geological evidence of past near-misses is fragmentary. The list begins in earnest from the late 1990s, when systematic asteroid surveys began.

Distance figures in this list are measured from Earth's surface, not from Earth's centre. Some published data uses geocentric distance (from the centre), which adds approximately 6,371 kilometres. A pass at 31,000 kilometres from the centre is roughly 24,600 kilometres from the surface.

Top 10 closest confirmed asteroid passes

Why small objects dominate the record books

The closest confirmed passes are all by objects under 10 metres. This is not a coincidence. Small asteroids vastly outnumber large ones. A 5-metre object can safely pass 300 kilometres above the surface without causing any harm, while a 300-metre object passing at the same distance would be a genuine planetary emergency.

Small objects are also the hardest to detect in advance. They reflect less sunlight and are invisible to current survey telescopes until they are very close, sometimes only hours before closest approach. Many of the records in this table were set by objects discovered after the event, which means the "record" was only recognised once the orbit was reconstructed from archival images.

The largest object to pass at a genuinely close distance in modern records is 2019 OK, estimated at 57-130 metres. It passed at roughly 73,000 kilometres and was detected only about 24 hours before closest approach. That event generated significant discussion in the planetary defence community about detection coverage for medium-sized objects.

The discovery timing problem

A striking feature of the closest approaches is how often they were discovered after the fact. 2020 VT4, 2020 QG, 2021 UA1, and 2002 EM7 were all identified only after their closest approach had already occurred. Astronomers found them by scanning archival images or by spotting the trail in survey data after the event.

This post-discovery pattern reveals the limits of current survey systems. Surveys are designed to scan large areas of sky repeatedly. A very fast-moving object on a trajectory that brings it from the Sun's direction (the "daylight blind spot") can reach close range before any telescope has a chance to catch it.

2023 BU is the positive counter-example: amateur astronomer Gennadiy Borisov detected it five days before closest approach, giving enough time for professional observatories to track it. Five days is a short warning for a 4-8 metre object, and entirely insufficient for anything larger. The Apophis 2029 flyby, by contrast, has been known about since 2004, giving two decades of preparation time.

Apophis 2029: a different kind of record

Apophis will not break the absolute miss-distance record: it is predicted to pass at roughly 31,000-32,000 kilometres from Earth's surface on 13 April 2029. That puts it well above the altitude of 2020 VT4's pass. But Apophis is approximately 370 metres across, making it far and away the largest asteroid ever predicted to pass this close in recorded history.

At that size, Apophis will be visible to the naked eye from Europe, Africa, and parts of Asia, moving visibly across the sky. It will pass closer than many geostationary satellites, which orbit at roughly 35,786 kilometres from Earth's centre. The pass presents an extraordinary opportunity for scientific observation, with multiple spacecraft missions planned to accompany it.

There is no impact risk in 2029. NASA removed Apophis from the Sentry risk table in 2021 following precise radar measurements that eliminated any impact possibility for at least the next century.

How detection is improving

The ATLAS survey system, designed specifically to detect impactors on short warning timescales, has improved detection of sub-50-metre objects substantially since coming online in 2017. The forthcoming NEO Surveyor space telescope, a NASA mission designed to observe in infrared from a Sun-Earth Lagrange point, will see objects approaching from the sunward direction that ground-based telescopes cannot reach. When operational, it is expected to significantly increase detection rates for objects that currently slip through the coverage gap that produced most of the post-discovery records in this list.