Asteroid 99942 Apophis is a near-Earth object (NEO) estimated to be about 1,100 feet (340 meters) acWhen it was discovered in 2004,
Apophis was identified as one of the most hazardous asteroids that could impact Earth. But that impact assessment changed after astronomers tracked Apophis, and its orbit became better determined.A radar observation campaign in March 2021, combined with precise orbit analysis, allowed astronomers to conclude that there is no risk of Apophis impacting our planet for at least a century.
Estimated to be about 1,100 feet (340 meters) across, Apophis quickly gained notoriety as an asteroid that could pose a serious threat to Earth when astronomers predicted that it would come uncomfortably close in 2029. Thanks to additional observations of Apophis, the risk of an impact in 2029 was later ruled out, as was the potential impact risk posed by another close approach in 2036. Until March 2021, however, a small chance of impact in 2068 still remained.
When Apophis made a distant flyby of Earth around March 5, 2021, astronomers took the opportunity to use powerful radar observations to refine the estimate of its orbit around the Sun with extreme precision, enabling them to confidently rule out any impact risk in 2068 and long after.
Exploration
Apophis was discovered on June 19, 2004, by astronomers Roy Tucker, David Tholen, and Fabrizio Bernardi at the Kitt Peak National Observatory in Tucson, Arizona. They were only able to observe the asteroid for two days because of technical and weather problems. Fortunately, a team at the Siding Spring Observatory in Australia spotted the asteroid again later in the same year.
Size and Distance
Apophis is about 1,100 feet (340 meters) in width. It’s expected to safely pass close to Earth – within 19,794 miles (31,860 kilometers) from our planet’s surface – on April 13, 2029. This will be the closest approach to Earth by an asteroid of this size that scientists have known about in advance. At its farthest, Apophis can reach a distance of about 2 astronomical units from Earth. One astronomical unit, abbreviated as AU, is the distance from the Sun to Earth.
Structure
Apophis is classified as an S-type, or stony-type asteroid made up of silicate (or rocky) materials and a mixture of metallic nickel and iron. Radar images suggest it is elongated and possibly has two lobes, making it look something like a peanut. Much more will be learned about this asteroid's structure following its close flyby of Earth in 2029.
Formation
Like all asteroids, Apophis is a remnant from the early formation of our solar system about 4.6 billion years ago. It originated in the main asteroid belt between Mars and Jupiter. Over millions of years, its orbit was changed primarily by the gravitational influence of large planets like Jupiter so that it now orbits the Sun closer to Earth. As a result, Apophis is classified as a near-Earth asteroid, as opposed to a main-belt asteroid.
Surface
There are no high-resolution images of the surface of asteroid Apophis, but it is likely similar to surfaces of other stony-type asteroids like Itokawa, the first asteroid from which samples were captured and brought to Earth for analysis.
How Apophis Got Its Name
Apophis is named for the demon serpent who personified evil and chaos in ancient Egyptian mythology.
Discovered By NASA
