Two Asteroids That Could Be As Big As Football Fields to Zip Past Earth

This week, two asteroids that could be as large as football fields will fly safely past the Earth.

The first of the pair of large space rocks to make a close approach to our planet is an object known as 2021 KC.

According to NASA's Center for Near Earth Object Studies (CNEOS,) the asteroid is estimated to measure somewhere between around 174 feet and 394 feet in diameter.

At the upper end of this size estimate, the asteroid would measure about the same length as a football field. It would also be slightly smaller than the Great Pyramid of Giza in Egypt.

Data from the CNEOS shows that 2021 KC will make a close approach to the Earth on May 21 at 11:36 p.m. Coordinated Universal Time (UTC), or 7:36 p.m. ET.

At this point, the space rock will come within around 1.9 million miles of the Earth, which is roughly eight times the average distance between our planet and the moon,

During its close approach, the asteroid will be travelling at around 17,600 miles per hour—more than eight times faster than the speed of a bullet fired out of a rifle.

The second space rock to zoom past our planet this week is called 2021 HJ2, and in some ways it has very similar characteristics to 2021 KC.

For example, 2021 HJ2 will make its close approach on the same day (for those in the western part of the Earth at least)—coming closest to our planet at 8:18 p.m. ET on May 21.

During the approach, the space rock will come within around 3.8 million miles of our planet—almost double the distance at which 2021 KC will fly past.

In fact, 3.8 million miles is roughly 16 times the average distance between the Earth and the moon—our only natural satellite.

But while 2021 HJ2 will not pass as close as 2021 KC, the two space rocks appear to be very similar in size.

CNEOS data shows that 2021 HJ2 is estimated to measure anywhere between around 167 feet and 361 feet in diameter—only slightly smaller than its predecessor. 2021 HJ2 will also be travelling at a similar speed—around 18,400 miles per hour.

These asteroids are near-Earth objects, or NEOs, essentially astronomical bodies in our cosmic neighborhood whose orbits around the sun can take them within 30 million miles of Earth's own orbital path.

Some NEOs are designated as "potentially hazardous," which refers to objects estimated to measure more than 460 feet in diameter that can approach within 4.6 million miles of the Earth's orbit.

An asteroid
Stock image showing an artist's rendering of an asteroid. Two football field-sized asteroids will fly past the Earth this week. iStock