Largest Asteroid to Fly Past Earth in 2021 'Potentially Hazardous'—Here's Why

On March 21, the largest known asteroid to fly past Earth in 2021 will make a close approach to our planet.

The enormous space rock—known as 2001 FO32—is one of numerous "near-Earth objects," or NEOs, that orbit the sun in our cosmic neighborhood.

This term refers to objects with trajectories that can take them within 30 million miles of Earth's own orbital path around the sun.

According to NASA's Center for Near Earth Object Studies (CNEOS) around 25,000 NEOs have been identified to date. The vast majority are asteroids and a handful are comets.

More than 2,100 of these near-Earth objects are classified as "potentially hazardous." But what does this term actually mean?

Potentially hazardous NEOs are those with orbits that approach the Earth's own path around the sun to within 4.6 million miles, while also measuring greater than around 460 feet in diameter.

CNEOS director Paul Chodas has previously told Newsweek that objects are classified as potentially hazardous because they are in orbits that "come close enough to Earth's that it is possible over many centuries and millennia they might evolve into Earth-crossing orbits. So it is prudent to keep tracking these asteroids for decades to come and to study how their orbits might be evolving."

The asteroid 2001 FO32 meets both these criteria. The CNEOS, which is based at NASA's Jet Propulsion Laboratory in California, estimates that it measures between 2,526 feet (0.47 miles) and 5,577 feet (1.05 miles) in diameter.

On March 21, the rock will come within about 1.3 million miles of our planet at 11:03 a.m. ET during its close approach.

NASA has several asteroid search programs that scan the skies every night. Once near-Earth objects are discovered, astronomers monitor them to understand their orbits and assess the chances that they could strike our planet.

Astronomers have already identified more than 95 percent of the really large asteroids—measuring 1 kilometer or 0.62 miles in diameter and larger—and none of them has a significant chance of colliding with the Earth over the next century, according to Chodas.

As it flies past the Earth, 2001 FO32 will be traveling at a staggering speed relative to the Earth at the time of its close approach—around 76,980 miles per hour.

This is around 100 times faster than the speed of sound and roughly a third as fast as a bolt of lightning when it travels from the atmosphere to the ground. The asteroid is the fastest traveling space rock to fly past the Earth this year.

Artist's illustration of an asteroid. iStock