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99942 Apophis (provisional designation 2004 MN 4) is a near-Earth asteroid and a potentially hazardous object, 450 metres (1,480 ft) by 170 metres (560 ft) in size, [3] that caused a brief period of concern in December 2004 when initial observations indicated a probability of 2.7% that it would hit Earth on Friday, April 13, 2029.
During the first decade of the 2000s, there were serious concerns the 325 metres (1,066 ft) wide asteroid 99942 Apophis posed a risk of impacting Earth in 2036. Preliminary, incomplete data by astronomers using ground-based sky surveys resulted in the calculation of a Level 4 risk on the Torino Scale impact hazard chart .
In a bit of ominous news befitting a Friday the 13th: It turns out that the asteroid Apophis could have a very small chance of colliding into Earth in five years, when it is expected to make a ...
For example, it was estimated there was a high chance of 99942 Apophis swinging by Earth in 2029 with a 10 −4 probability of returning on an impact trajectory in 2035 or 2036. It was then determined that a deflection from this potential return trajectory, several years before the swing-by, could be achieved with a velocity change on the order ...
Within a few years, they were able to dismiss the even smaller chance of a hit in 2036. Images of the asteroid Apophis, captured in 2012, allowed scientists to determine that it will not strike ...
A second example was the 2013 ESA Herschel Space Observatory follow-up observations of 99942 Apophis, which showed it was 20% larger and 75% more massive than previously estimated. [65] However such follow-ups are rare. The size estimates of most near-Earth asteroids are based on visible light only. [66]
Apophis is of interest because it’s an S-type, or stony, asteroid — different from other space rocks visited by NASA missions, including Bennu, which is a C-type, or carbonaceous, asteroid.
This is a list of asteroids that have impacted Earth after discovery and orbit calculation that predicted the impact in advance. As of December 2024, all of the asteroids with predicted impacts were under 5 m (16 ft) in size that were discovered just hours before impact, and burned up in the atmosphere as meteors.