Asteroid Potentially Taller Than Golden Gate Bridge to Whizz Past Earth After Asteroid Day

A huge asteroid potentially taller than the Golden Gate Bridge is due to fly past the Earth on Thursday—the day after Asteroid Day.

The space rock, which is tracked by NASA's Center for Near Earth Object Studies (CNEOS), is estimated to be between 360 and 820 feet in diameter.

To put that into context, each tower of the Golden Gate Bridge sits around 746 feet above San Francisco Bay.

The asteroid, called 2021 GM4, is expected to be traveling at over 6 kilometers per second (13421.6 miles per hour) when it passes our planet on Thursday—more than six times faster than a rifle bullet.

Thankfully it won't get close. CNEOS predicts that 2021 GM4 will pass Earth at a distance of 2.8 million miles, around 12 times as far as the Earth is from the moon. The exact time of its closest approach is estimated to be 7:53 p.m. EDT.

CNEOS judges 2021 GM4 to be a Potentially Hazardous Asteroid (PHA) based on a number of parameters used to measure the space rock's potential to hit Earth.

These criteria show that an asteroid must, at some point, get closer to Earth than 4.65 million miles and be bigger than around 500 feet in diameter.

CNEOS currently tracks around 26,000 near-Earth asteroids. Of those, around 1,000 are thought to be more than 1 kilometer in diameter.

2021 GM4 will not be the only large space rock to pass by Earth on Thursday. Another, smaller asteroid called 2010 XJ11 will also pass our planet at a distance of around 966,740 miles at 12:35 p.m. EDT.

It is predicted to be potentially as big as 324 feet across—roughly the same size as an NFL football field is long.

This Wednesday marks Asteroid Day, a U.N.-sanctioned annual event aimed at increasing public awareness of the risks associated with asteroid impacts. Asteroid Day is run by the Asteroid Foundation.

This year's event is due to include presentations by scientists and space experts on asteroid-related topics, including updates on NASA projects such as the OSIRIS-REx mission to asteroid Bennu.

The 2021 program list also shows that Brain May, widely known as the guitarist for rock band Queen, is due to talk about stereoscopic imagery and asteroids. May is an astrophysicist, and received a PhD in astrophysics from Imperial College London in 2007.

An event livestream is due to start at 12:00 p.m. EDT on Wednesday and can be found on AsteroidDay.org.

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A stock photo shows an asteroid hurtling through space. NASA tracks thousands of space rocks using its CNEOS branch. Mark Garlick/Getty