Record Passes

The closest asteroids
ever to pass Earth

The record holder passed just 3,600 km above the surface - closer than many operational satellites. Here are the closest confirmed non-impacting passes in the historical record.

Famous historical approaches →

Record close passes

Distances are measured from Earth's surface. One lunar distance (LD) = 384,400 km. Note that many small objects pass undetected, so this is a record of known passes.

Asteroid	Date	Distance (surface)	In LD	Size	Note
2023 BU	26 Jan 2023	~3,600 km	~0.009 LD	4–8 m	Confirmed record - closest non-impacting pass
2011 CQ1	4 Feb 2011	~5,480 km	~0.014 LD	~1 m	Tiny object, gravitational flyby altered its orbit
2004 FH	18 Mar 2004	~43,000 km	~0.11 LD	~30 m	Inside GEO altitude, visible to small telescopes
2012 TC4	12 Oct 2017	~44,000 km	~0.11 LD	~17 m	Used as a planetary defence exercise by ESA and NASA
2020 VT4	13 Nov 2020	~370 km	~0.001 LD	~5 m	Passed below many operational satellites. Discovered after flyby.
Apophis (2029)	13 Apr 2029	~32,000 km	~0.10 LD	~370 m	Closest pass by a known large asteroid. Naked-eye visible.

2023 BU - the record holder

Asteroid 2023 BU was discovered by amateur astronomer Gennadiy Borisov on 21 January 2023 - just five days before its closest approach. At 4-8 metres across, it was a small object, but its trajectory was extraordinary: it passed 3,600 km above Earth's surface on 26 January 2023, well below the altitude of geostationary satellites at 35,786 km from Earth's centre.

Earth's gravity significantly altered its trajectory during the flyby, changing its orbital period from roughly 359 days to around 425 days. This type of gravitational deflection is well understood and was predicted accurately in advance.

An object of that size posed no real risk even if it had been aimed directly at Earth - it would have disintegrated in the atmosphere. The significance of 2023 BU is that it set a measurable benchmark for how close a known asteroid has come to Earth without striking it.

The next notable approach: Apophis, 2029

While 2023 BU holds the distance record, Apophis will hold the record for the closest pass by a large known asteroid. At roughly 370 metres across, it will pass approximately 38,000 km from Earth's centre on 13 April 2029 - close enough to be visible to the naked eye over large parts of the world.

Apophis carries no impact risk for that encounter. Scientists will use the 2029 flyby for intensive study, as Earth's gravity will slightly alter its orbit - the precision of post-flyby tracking will help refine long-term impact probability calculations for subsequent encounters.

How close do asteroids pass Earth?

Miss distance units and what they mean.

Apophis asteroid

Details on the 2029 flyby - the closest known large asteroid pass.

Famous historical flybys

Notable approaches that shaped planetary science.

Next close approach

Live countdown to the next upcoming flyby.

Common questions

Which asteroid holds the record for closest confirmed pass without hitting Earth?

Asteroid 2023 BU passed approximately 3,600 km above Earth's surface on 26 January 2023 - the closest confirmed non-impacting pass by a known asteroid on record. At that altitude, it was well below the orbit of geostationary satellites (35,786 km from Earth's centre) and closer than most low-Earth orbit satellites. The object was estimated at 4-8 metres across.

How close is the Apophis 2029 flyby?

Apophis will pass approximately 38,000 km from Earth's centre in April 2029 - placing it in the vicinity of geostationary satellites. At roughly 370 metres across, it will be visible to the naked eye over parts of Europe, Africa, and Asia. The pass carries no impact risk. It will be the closest known pass by an object of that size in recorded history.

Did 2023 BU pass closer than any satellite?

It passed closer than geostationary satellites, which orbit at around 35,786 km from Earth's centre. At roughly 3,600 km above the surface, 2023 BU was briefly inside the zone used by low-Earth orbit satellites (which typically orbit from 160 to 2,000 km altitude) - though it passed safely through without incident. Objects in that size range are so numerous and poorly catalogued that this was not unusual in frequency, only in the late timing of its discovery.

Are there closer passes that went undetected?

Almost certainly. Objects at the smaller end of the scale - under 10 metres - are difficult to detect at all unless they pass within a few thousand km or enter the atmosphere. Many small asteroids pass inside the Moon's orbit without being detected beforehand. The number of undetected passes at distances less than 1 lunar distance (384,400 km) is likely far higher than the catalogue suggests. Detection is improving as telescope sensitivity increases.

What was the first asteroid to be detected before impact?

2008 TC3 was the first asteroid detected before it hit Earth. Discovered on 6 October 2008, it struck the atmosphere over Sudan approximately 19 hours later - too small and too late to deflect, but enough time to alert researchers who subsequently recovered meteorite fragments from the Nubian Desert. It was roughly 4 metres across.