On April 13, 2029, the asteroid known as 99942 Apophis, nicknamed the 'God of Chaos,' will make an exceptionally close flyby of Earth, passing within approximately 19,000 miles (30,600 kilometers) of the planet's surface. This distance is closer than the orbits of some geosynchronous satellites. New maps revealed at the Apophis T-3 Years workshop in Padua, Italy, indicate that the asteroid will be visible to about 90% of the world's population with the naked eye.
At approximately 450 meters (1,500 feet) wide, Apophis is large enough to be considered a 'city killer' asteroid. When discovered in 2004, initial calculations suggested a one in 37 chance of impact with Earth. However, subsequent observations and trajectory recalculations have reduced the probability of a collision in the next 100 years to zero. Scientists have emphasized that there is no risk of impact during this upcoming flyby.
Apophis will be visible as a bright, star-like object slowly traversing the sky for several hours. Unlike meteors that glow from atmospheric entry, Apophis will be seen by reflecting sunlight, making it visible during twilight and nighttime hours. Scientists expect an estimated 7.6 billion people to have an opportunity to observe this event.
The flyby will begin around 3:00 PM GMT, when Apophis is furthest from Earth, offering viewing opportunities for billions in Australia and Asia. The closest approach, occurring at approximately 9:45 PM GMT, will make the asteroid visible to nearly 2 billion people across eastern South America, northern Africa, and parts of Europe. The asteroid will reach its zenith over the North Atlantic and begin to fade from view around 10:00 PM GMT.
The moment of maximum brightness, predicted for 8:35 PM GMT, is anticipated to be the best time for viewing. At this point, Apophis is expected to resemble one of the brightest stars in the Big Dipper and will move across the sky at a speed equivalent to the width of a full moon per minute. For viewers in the United Kingdom, Apophis will become visible with twilight around 8:00 PM GMT and remain observable as night falls.
Professor Richard Binzel, a planetary scientist at MIT involved in mapping the flyby, described the event as a unique opportunity for the public to witness an asteroid's perceptible movement against the background stars. He also highlighted its significance for astronomers studying asteroids, providing crucial data on their composition and the effects of planetary tidal forces.
Scientists are particularly interested in how Earth's gravity may affect Apophis's orbit during this close encounter. Research suggests that the gravitational pull could alter its trajectory, potentially making future collisions more likely, though still improbable within the next century. Telescopes on Earth and several spacecraft, including NASA's OSIRIS-APEX mission, will observe Apophis to detect any changes in its structure or path.
The data gathered from Apophis's flyby is considered vital for future planetary defense strategies. Understanding the characteristics of smaller asteroids like Apophis can inform the best methods for deflecting potentially Earth-bound objects. This knowledge is crucial, as current capabilities are limited to mitigating impacts rather than preventing them entirely, as demonstrated by NASA and the European Space Agency's DART mission, which tested an asteroid deflection technique.
