Apophis — 99942

historic flyby · 13 April 2029 · 21:46 UTC

T-dhms

The most-watched asteroid of the century will pass 31,637 km above Earth's surface — just 10% of the distance to the Moon — closer than some of our satellites.

distance to Earth

lunar distances

current relative velocity

99942 / Asteroid data

Apophis by the numbers

Discovered on 19 June 2004 by Roy Tucker, David Tholen, and Fabrizio Bernardi. In its first weeks it reached a 2.7% impact probability — the highest ever recorded for a known asteroid. Goldstone radar ruled it out definitively in 2021.

Estimated diameterdimension: 375 m≈ height of the Eiffel Tower
MassSq-type, silicate: ~6 × 10¹⁰ kg≈ 10× the Great Pyramid of Giza
Rotation periodchaotic rotation (tumbling): 30.6 h
Relative velocity at perigee13 Apr 2029: 7.42 km/s
Orbital semi-major axisperiod 323.6 days: 0.918 AU

FAQ / Common questions

What you need to know

Will Apophis hit Earth?: No. In March 2021, precise radar observations from Goldstone reduced the impact probability to zero for 2029 and for at least the next hundred years.
How close will it get?: About 31,600 km from Earth's surface (38,015 km from its centre) — closer than geostationary satellites, which orbit at 35,786 km altitude, and roughly 10 times closer than the Moon. At its closest, some satellites will actually be farther from Earth than Apophis.
Will it be visible to the naked eye?: Yes. From Europe, Africa, and western Asia it will reach apparent magnitude 3.1 — visible without optical aid as a slow-moving point of light crossing the sky over several hours on the night of 13 April 2029.
What would happen if it hit?: At 375 metres across, an Apophis impact would release an estimated 1,200 megatons of TNT — on the order of tens of thousands of Hiroshima-scale weapons. It would cause catastrophic regional devastation — the destruction of a large city and surroundings — but is not an extinction-level event.
Which missions will study it?: Several spacecraft will be in the vicinity. RAMSES (ESA, approved 2025) is set to arrive in February 2029 and orbit Apophis before, during and after the flyby. OSIRIS-APEX (NASA) will rendezvous with the asteroid a few weeks after perigee and study it for 18 months. Exploration Labs' Apophis EX aims to be the first commercial rendezvous with an asteroid.
Why is it named Apophis?: The discoverers — Roy Tucker, David Tholen, and Fabrizio Bernardi — named it after the ancient Egyptian god of chaos: the great serpent who tried each night to devour the sun god Ra. The name reflected the alarm of its early impact calculations.

Apophis by the numbers

Estimated diameterdimension

375 m≈ height of the Eiffel Tower

MassSq-type, silicate

~6 × 10¹⁰ kg≈ 10× the Great Pyramid of Giza

Rotation periodchaotic rotation (tumbling)

30.6 h

Relative velocity at perigee13 Apr 2029

7.42 km/s

Orbital semi-major axisperiod 323.6 days

0.918 AU

What you need to know

Will Apophis hit Earth?

No. In March 2021, precise radar observations from Goldstone reduced the impact probability to zero for 2029 and for at least the next hundred years.

How close will it get?

About 31,600 km from Earth's surface (38,015 km from its centre) — closer than geostationary satellites, which orbit at 35,786 km altitude, and roughly 10 times closer than the Moon. At its closest, some satellites will actually be farther from Earth than Apophis.

Will it be visible to the naked eye?

Yes. From Europe, Africa, and western Asia it will reach apparent magnitude 3.1 — visible without optical aid as a slow-moving point of light crossing the sky over several hours on the night of 13 April 2029.

What would happen if it hit?

At 375 metres across, an Apophis impact would release an estimated 1,200 megatons of TNT — on the order of tens of thousands of Hiroshima-scale weapons. It would cause catastrophic regional devastation — the destruction of a large city and surroundings — but is not an extinction-level event.

Which missions will study it?

Several spacecraft will be in the vicinity. RAMSES (ESA, approved 2025) is set to arrive in February 2029 and orbit Apophis before, during and after the flyby. OSIRIS-APEX (NASA) will rendezvous with the asteroid a few weeks after perigee and study it for 18 months. Exploration Labs' Apophis EX aims to be the first commercial rendezvous with an asteroid.

Why is it named Apophis?

The discoverers — Roy Tucker, David Tholen, and Fabrizio Bernardi — named it after the ancient Egyptian god of chaos: the great serpent who tried each night to devour the sun god Ra. The name reflected the alarm of its early impact calculations.