Asteroid Apophis: the close approach of 2029
On 13 April 2029 asteroid 99942 Apophis passes roughly 31,600 km above Earth’s surface — nearer than our geostationary satellites. It will not hit, and that is now settled, not a hope.
Updated on October 7, 2026
The numbers
- Designation
- 99942 Apophis
- Discovered
- 19 June 2004, Kitt Peak
- Diameter
- about 340 m
- Date of the close approach
- 13 April 2029
- Distance above the surface
- about 31,600 km
- For comparison, geostationary orbit
- 35,786 km
- Impact risk, next 100 years
- ruled out
- Removed from the Sentry risk list
- March 2021
- Visible to the naked eye in 2029
- yes, from Europe, Africa and western Asia
Source: NASA/JPL — Center for Near-Earth Object Studies (CNEOS)
How the scare was settled
Shortly after its discovery in 2004, Apophis briefly reached level 4 on the Torino scale, the highest any asteroid has been given, with an estimated 2.7% chance of hitting Earth in 2029. That number came from a short observation arc: with only a few days of data the orbit was loose enough to include Earth. Every further observation tightened it, and the 2029 impact was excluded within months.
A smaller worry survived longer. If the 2029 pass had sent the asteroid through a narrow "keyhole" region, a later return in 2068 could have been dangerous. Radar observations in March 2021 nailed the orbit precisely enough to rule that out too, and NASA removed Apophis from the Sentry risk table. There is no impact risk for at least a century.
Source: NASA/JPL — Center for Near-Earth Object Studies (CNEOS)
Why 2029 is a gift to science
An object this size comes this close roughly once every few thousand years, and this time we know about it in advance. Earth’s gravity will visibly reshape the orbit and may change how the asteroid spins, and possibly resurface it — a natural experiment nobody could stage. ESA is preparing the Ramses mission to be in place beforehand, and NASA has redirected the OSIRIS-REx spacecraft, now renamed OSIRIS-APEX, to arrive shortly after the flyby.
Source: NASA/JPL — Center for Near-Earth Object Studies (CNEOS)
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The size of which tower
Apophis’s roughly 340-metre diameter comes within a whisker of the Eiffel Tower’s height (330 m) — a ratio of 1.03. Picturing the whole tower, end to end, passing 31,600 km from Earth helps gauge the size in "Asteroid Apophis: the close approach of 2029" without over- or under-stating the 2004 scare.
Words on this page
Astronomical unit
The solar system’s reference distance, fixed at exactly 149,597,870,700 metres since 2012, close to the average Earth–Sun distance. It saves writing every planet’s orbit in kilometres with ten digits.
Standard definition by IAU — International Astronomical Union · Astronomical unit
Launch window
The span of time in which a rocket can lift off and still reach its planned orbit or destination. For a trip to another planet that window can last only a few weeks and only returns at the next favourable alignment, so missing it costs months or years of waiting.
Exoplanet
A planet orbiting a star other than the Sun. Most were found indirectly, by the star’s faint dimming as the planet crosses in front of it (transit) or by the gravitational wobble it causes in the star (radial velocity), not by direct image.
Standard definition by NASA Exoplanet Archive · Exoplanet
Standard uncertainty
The margin attached to a measured value, usually written in parentheses on the last digits. A constant that is "exact by definition" has zero standard uncertainty; a measured one, like the gravitational constant G, always carries some.
Standard definition by BIPM — Bureau International des Poids et Mesures (SI) · Standard uncertainty
Atomic number
The number of protons in an atom’s nucleus, written Z. It is this number, not the mass, that defines which element an atom is: every atom with 8 protons is oxygen, whether it has 8 or 18 neutrons.
Standard definition by IUPAC · Atomic number