Current Orbital Data and Physical Characteristics of Apophis
Apophis is a near-Earth asteroid with a mean diameter of about 370 meters, classified as an Aten-group asteroid. Radar and optical observations from ground-based telescopes and space agencies have refined its orbit, showing a semi-major axis of roughly 0.92 AU and an orbital period of about 0.89 years. The latest trajectory solutions place its closest approach to Earth in 2029 at a distance of about 31,000 kilometers from Earth's center, or roughly 3,200 kilometers above the surface, a pass well within the geostationary satellite belt. Follow-up astrometric campaigns continue to reduce orbital uncertainty, and the current cumulative impact probability for the 2029 and 2036 keyholes is effectively zero according to the Sentry risk table. The Yarkovsky acceleration, a thermal recoil effect, remains a key parameter in long-term predictions, and ongoing radar campaigns at facilities such as Goldstone and Green Bank refine the semi-major axis to sub-kilometer precision NASA JPL Small-Body Database.
Apophis was discovered in 2004 and initially generated concern because early orbital solutions indicated a possible impact in 2029. Subsequent radar observations in 2005 and 2008, along with precovery images, removed the 2029 impact scenario and later ruled out the 2036 keyhole. The asteroid's shape, determined from radar imaging, is elongated and bilobed, with dimensions estimated at roughly 450 by 170 meters. Its spectral type is classified as Sq-type in the Bus-DeMeo taxonomy, consistent with an stony S-type composition. Absolute magnitude H is approximately 19.7, giving a geometric albedo around 0.23, which implies a moderate reflectivity similar to fresh asphalt JPL SBDB Lookup for Apophis.
2029 Close Approach, Keyhole Dynamics, and Observational Campaigns
The 2029 close approach will occur on April 13, 2029, at 21:46 UTC, with a nominal miss distance of about 31,600 kilometers from Earth's center. During this pass, Apophis will become visible to the naked eye from parts of Europe, Africa, and western Asia, reaching an apparent magnitude of about 3.1 to 3.4. The flyby will take the asteroid through a narrow gravitational keyhole in space; a passage through the 2029 keyhole of roughly 600 meters wide would set up a future impact on April 13, 2036, but current orbit solutions place the miss far outside this corridor. The 2029 encounter will also alter Apophis's orbit, changing its semi-major axis by about 1.7 kilometers and increasing its orbital period by roughly 30 seconds. This keyhole dynamics is a classic example of resonant return and gravitational perturbation, and it is actively studied by the IAWN and MPC communities The Planetary Society Apophis Overview.
Observational campaigns for the 2029 approach include radar imaging campaigns at Goldstone, the Green Bank Telescope, and the Very Long Baseline Array, as well as optical follow-up by the Catalina Sky Survey and the ATLAS network. Space-based assets such as the Hubble Space Telescope and the James Webb Space Telescope are planned for thermal and spectroscopic observations during the close approach. The