Asteroid the Size of One of Ancient Egypt's Giza Pyramids Is One of Three Huge Space Rocks to Pass Earth Today

Three asteroids will pass safely by Earth today, two of which are about the same size as one of the pyramids at the famous Giza complex in Egypt.

The first of these space rocks, known as 2015 HM10, has already made its closest approach when it came within about 2.9 million miles of our planet at 2:00 a.m. EDT this morning. The asteroid—which is estimated to measure up to 360 feet in diameter—whizzed past at speeds of around 21,000 miles per hour relative to the Earth.

The second of the asteroids—2019 OD—is estimated to be about the same size as 2015 HM10, according to NASA's Center for Near Earth Object Studies (CNEOS.) It will make its closest approach at 9:31 a.m. EDT at a much smaller distance of 221,234 miles which may seem like a long way away, but in cosmic terms it's not far at all. In fact, the asteroid will actually travel within the average distance between the moon and the Earth, which is 238,855 miles.

2019 OD will also be moving much faster than 2015 HM10 with the CNEOS estimating its speed to be more than 42,900 miles per hour.

For a size comparison, the diameter of these two asteroids is roughly the same as the base of the Pyramid of Menkaure—the smallest of the three main Pyramids in the Giza complex.

Stock photo: Three asteroids will pass by Earth today. iStock

The final asteroid to make a close approach today—2019 OE—is significantly smaller than the previous two, estimated to measure between 79 and 174 feet in diameter. At its closest approach, the space rock will come within 598,635 miles of our planet, or around 2.5 times the Earth-Moon distance.

All three of the space rocks are classified as Near-Earth Objects (NEOs)—a term which refers to any asteroid or comets whose orbit takes it within 121 million miles of the sun.

NASA's CNEOS computes the orbits of known NEOs to determine whether any have a chance of striking the Earth at some point in the future. Those which are predicted to have a minimum approach distance of less than 4.6 million miles and are estimated to measure more than 460 feet in diameter are deemed "potentially hazardous" even though none are currently thought to have a realistic chance of colliding with our planet in the foreseeable future.

"There are some asteroids which have an exceedingly small chance of impacting Earth over the next couple centuries," CNEOS Manager Paul Chodas told Newsweek. "Asteroid Bennu, which is currently being visited by the OSIRIS-REx spacecraft, currently has a one-in-a-few-thousand chance of impacting a couple centuries from now, but as we continue to track this asteroid, I expect that chance to drop to zero. None of the other known asteroids has a significant chance of impacting Earth over the next century."

We currently know about more than 20,000 NEOs—the vast majority of which are asteroids—although NASA estimates that two-thirds of these objects larger than 460 feet in diameter in the solar system are yet to be discovered.