Later today, our planet will gain a fleeting visitor: an asteroid about the size of a city block will pass by at about half the distance to the moon. While there is no reason for concern about it hitting the Earth – NASA has determined that it poses no threat – it will be one of the closest passes of an asteroid this size yet observed.
The asteroid, which is officially named 2010 WC9, will be at its closest to the Earth at 6:05 pm EDT this evening. 2010 WC9 is on the small side as far as asteroids go, measuring between 197 to 427 feet. But despite its unremarkable size, it’s quite notable in terms of its proximity. As Eddie Irizarry reports for EarthSky, this flyby will be the closest this particular asteroid has come to the Earth in over 300 years, whizzing past at a distance of 126,000 miles from our planet’s surface.
Though astronomers at the Catalina Sky Survey discovered this asteroid back in November 2010, it disappeared from sight a month later. The asteroid remained hidden from view until just last week. Finally able to track the space rock's path, astronomers quickly predicted the asteroid's path, finding it will pass by Earth at a close, but not catastrophic, distance.
2010 WC9 is one of nearly 10,000 asteroids classified in the Apollo group, which is a class of near-Earth space rocks that cross over our planet’s orbit in their trips around the sun. NASA classifies roughly 1,900 of known space rocks as Potentially Hazardous Asteroids (PAH), based on their calculated to threaten Earth. Thankfully, 2010 WC9 does not fall in this category.
As NBC’s David Freeman writes, asteroids of 2010 WC9’s size shouldn’t be too much cause for concern as they’re only thought to make contact with our planet just once every 6,000 years.
If this asteroid were coming close enough to hit Earth, though, it could really wreak havoc. It is estimated to be larger than the Chelyabinsk meteor, which exploded in the skies over Russia in 2013, producing a large shock wave and many small meteorites. The blast caused 1,500 injuries, which were mainly due to shattered glass, Deborah Byrd reported for EarthSky in 2016. And depending on WC9’s makeup, if it were to collide with our planet, it could be powerful enough to make a crater almost a mile wide, Erin Ryan, an astrophysicist at NASA’s Goddard Space Flight Center, tells NBC.
For those hoping to catch a glimpse of the space rock, WC9 may prove elusive without a telescope. Given its small size and brisk pace of 28,655 miles per hour, the asteroid will not be visible to the naked eye when it passes this evening. But astronomy enthusiasts lacking telescopes will still be able to see it; Northholt Branch Observatories in London will be livestreaming the event on Facebook.
There’s no need to take cover later today – the odds of an asteroid strike are vanishingly small. But we will get the treat of taking a closer look at 2010 WC9 before it hurtles away on its orbit of the sun.