Apophis (Asteroid 99942) is a large, near-Earth asteroid roughly \(1,115\) feet in diameter. Named after the ancient Egyptian god of chaos and darkness, it made global headlines in 2004 when initial calculations suggested a small chance of it hitting Earth in 2029. NASA has since confirmed there is no risk of an impact for at least the next 100 years.The 2029 Close Approach On Friday, April 13, 2029, Apophis will make one of the closest asteroid flybys in recorded history for a space rock of this size.Distance: It will pass within \(20,000\) miles (\(32,000\) km) of Earth's surface, which is inside the orbit of many geosynchronous satellites.Visibility: The asteroid will be visible to the naked eye from parts of Europe, Africa, and Asia as a speck of light moving across the night sky.Scientific Significance Because the flyby is so close, Earth's immense gravity will physically interact with the space rock.Tidal Forces: Our planet's gravity is expected to stretch and squeeze the asteroid, potentially triggering minor quakes and landslides on its surface and altering its rotation.Orbital Shift: The gravitational tug will actually change Apophis's orbit around the Sun, transitioning it from an Aten-class to an Apollo-class asteroid.Because it presents a rare opportunity for planetary defense and space observation without actually threatening the planet, multiple space agencies and universities are actively preparing missions and instruments to track and study the asteroid during its 2029 approach.Track its orbit and follow mission updates on NASA Science.Apophis - NASA Science When Apophis was discovered in 2004, it appeared the asteroid could potentially impact Earth in the coming decades.

2029 close approach

The closest known approach of Apophis will occur on 13 April 2029, at 21:46 UT, when Apophis will pass Earth at a distance of about 31,600 kilometres (19,600 mi) above the surface. Using the June 2024 orbit solution which includes the Yarkovsky effect, the 3-sigma uncertainty region in the 2029 approach distance is about ±3.3 km. The distance, a hair's breadth in astronomical terms, is five times the radius of the Earth, one tenth the distance to the Moon, and closer than the ring of geostationary satellites currently orbiting the Earth. It will be the closest asteroid of its size in recorded history. On that date, it will become as bright as magnitude 3.1 (visible to the naked eye from rural as well as darker suburban areas, visible with binoculars from most locations). The close approach will be visible from Europe, Africa, and western Asia. Over the course of about a day, Apophis will move northwest from Centaurus to Perseus and then southwest to Pisces, an arc of 205°. Approaching Earth its speed relative to Earth will be 6.0 km/s. Earth's gravity will accelerate it to 7.4 km/s at the time of closest approach, and then slow it back down to 6 as it departs. During the approach, Earth will perturb Apophis from an Aten-class orbit with a semi-major axis of 0.92 AU to an Apollo-class orbit with a semi-major axis of 1.1 AU. Perihelion will lift from 0.746 AU to 0.895 AU and aphelion will lift from 1.10 AU to 1.31 AU.
Orbital elements for 2029 (pre-flyby) and 2030 (post-flyby)[53] Parameter
Epoch Orbit
type Orbital
period Semi-major
axis Perihelion Aphelion Inclination Eccentricity
Units AU (°)
Pre-flyby 2029 Aten 0.89 years (323.6 days) 0.922 0.746 1.10 3.34° 0.191
Post-flyby 2030 Apollo 1.16 years (423.1 days) 1.103 0.895 1.31 2.22° 0.189

Apophis also encounters the Moon at 89,600 km (55,700 mi) from the lunar surface, 16 hours after the encounter with Earth.

During the 2029 approach, Apophis's brightness will peak at magnitude 3.1, easily visible to the naked eye, with a maximum angular speed of 42° per hour. The maximum apparent angular diameter will be approximately 2 arcseconds. This is roughly equivalent to the angular diameter of Neptune from Earth. Therefore, the asteroid will be barely resolved by ground-based telescopes not equipped with adaptive optics but very well resolved by those that are. Because the approach will be so close, tidal forces are likely to alter Apophis's rotation axis, but Apophis will not approach within the Roche limit where it would be broken up by tidal forces. A partial resurfacing of the asteroid is possible, which might change its spectral class from a weathered Sq- to an unweathered Q-type.

2036 approaches

In 2036, Apophis will pass the Earth at a third the distance of the Sun in both March and December. Using the 2024 orbit solution, the Earth approach on 27 March 2036, will be no closer than 0.3089 AU (46.21 million km; 28.71 million mi; 120.2 LD), but more likely about 0.3097 AU (46.33 million km; 28.79 million mi). For comparison, the planet Venus will be closer to Earth at 0.2883 AU (43.13 million km; 26.80 million mi; 112.2 LD) on 30 May 2036. On 31 December 2036, Apophis will be a little bit further away than the March approach at about 0.33 AU (49 million km; 31 million mi).
2051 approach

Around 19–20 April 2051, Apophis will pass about 0.04 AU (6.0 million km; 3.7 million mi) from Earth and it will be the first time since 2029 that Apophis will pass within 10 million km of Earth.
2066 and 2068

Although early simulations showed that there was a chance Apophis could hit the earth on 12 April 2068, this was later excluded and JPL Horizons calculates that Apophis will be about 1.864 ± 0.0024 AU (278.85 ± 0.36 million km) from Earth, making the asteroid much farther than the Sun.

By 2116, the JPL Small-Body Database and NEODyS close approach data start to become divergent. In April 2116, Apophis is expected to pass about 0.02 AU (3 million km; 8 LD) from Earth, but could pass as close as 0.001 AU (150 thousand km; 0.39 LD) or as far as 0.1 AU (15 million km; 39 LD).
Refinement of close approach predictions

Six months after discovery, and shortly after a close approach to Earth on 21 December 2004, the improved orbital estimates led to the prediction of a very close approach on 13 April 2029, by both NASA's automatic Sentry system and NEODyS, a similar automatic program run by the University of Pisa and the University of Valladolid. Subsequent observations decreased the uncertainty in Apophis's trajectory and the probability of an impact event in 2029 temporarily climbed, peaking at 2.7% (1 in 37) on 27 December 2004, When the uncertainty region had shrunk to 83,000 km. This probability, combined with its size, caused Apophis to be assessed at level 4 on the Torino scale[16] and 1.10 on the Palermo scale (corresponding to an impact hazard over 12 times the background level), scales scientists use to represent how dangerous a given asteroid is to Earth. These are the highest values at which any object has been rated on either scale. The chance that there would be an impact in 2029 was eliminated later in the day of 27 December 2004, as a result of a precovery image that extended the observation arc back to March 2004 The danger of a 2036 passage was lowered to level 0 on the Torino scale in August 2006. With a cumulative Palermo scale rating of −3.22, the risk of impact from Apophis is less than one thousandth the background hazard level.

In July 2005, former Apollo astronaut Rusty Schweickart, as chairman of the B612 Foundation, formally asked NASA to investigate the possibility that the asteroid's post-2029 orbit could be in orbital resonance with Earth, which would increase the probability of future impacts. Schweickart also asked NASA to investigate whether a transponder should be placed on the asteroid to enable more accurate tracking of how its orbit is affected by the Yarkovsky effect. 2011 observations