• Asteroid 332446 (2008 AF4) is categorized by NASA as a potentially hazardous asteroid (PHA)
  • The asteroid is set to pass by Earth Wednesday at 5:52 p.m. EST
  • The space rock is not on the ESA's Risk List, which means it is not expected to hit Earth during its flyby

NASA's Center for Near-Earth Object Studies (CNEOS) is keeping a close eye on a massive asteroid that is set to pass by Earth Wednesday.

Asteroid 332446 (2008 AF4) is categorized by NASA as a potentially hazardous asteroid (PHA). PHAs are near-Earth objects (NEO) that have the potential to make close approaches to the planet and are large enough to cause significant damage if they enter the atmosphere and crash to the ground.

"Potentially Hazardous Asteroids (PHAs) are currently defined based on parameters that measure the asteroid's potential to make threatening close approaches to the Earth. Specifically, all asteroids with an Earth Minimum Orbit Intersection Distance (MOID) of 0.05 au or less and an absolute magnitude (H) of 22.0 or less are considered PHAs," CNEOS explained on its website.

The space rock, which is expected to make its close approach to Earth at 5:52 p.m. EST on Wednesday, is estimated to be taller than the CN Tower in Canada. The tower, which houses the longest metal staircase in the world, stands 1,814 feet (553 meters) tall, while asteroid 332446 (2008 AF4) measures about 2,230 feet (680 meters) across.

The asteroid's diameter is also nearly equal to the height of the Burj Dubai, according to The Measure of Things' calculations. Burj Khalifa, the tallest manmade structure in the world, stands 2,716 feet (828 meters) tall.

Fortunately, the asteroid has not been included in the European Space Agency's Risk List, which means it is not expected to hit Earth during its upcoming flyby.

According to NASA, a space rock larger than 25 meters but smaller than 1 kilometer (a little more than half a mile) would "cause local damage to the impact area" if it were to hit Earth. Asteroids that are larger than 1 to 2 kilometers are expected to pose a threat to the entire planet if they collide with Earth.

CNEOS' Close Approach Data Table reported that asteroid 332446 (2008 AF4) is currently moving at a speed of 22,000 miles per hour (35,000 kilometers per hour) and would get as close as 2 million miles (3 million kilometers) away from the planet's surface when it passes by.

First discovered in June 2002, asteroid 332446 (2008 AF4) is considered an Apollo asteroid due to its Earth-crossing orbit. NEOs in this category follow orbits that intersect with that of the Earth, making close approaches more likely to happen.

Aside from Apollo, other categories of asteroids include Amor, Aten and Atira. Similar to Apollo asteroids, Atens also follow Earth-crossing orbits but with semi-major axes smaller than that of the planet.

The left-hand image shows SPHERE observations of Asteroid 1999 KW4. The angular resolution in this image is equivalent to picking out a single building in New York — from Paris. An artist's impression of the asteroid pair is shown on the right. ESO