Newly-discovered asteroid barely misses us, makes one of the closest ever flybys of Earth
Just shy of a week ago, on the evening of Tuesday, June 3, a truck-sized asteroid zipped past Earth, coming well within the orbit of our geosynchronous satellites, and making one of the closest flybys ever detected.
Asteroid 2014 LY21 was first detected on Monday, June 2, by the Mt. Lemmon Survey, which is part of the Catalina Sky Survey. Spotted while it was still outside the orbit of the Moon and slightly 'ahead' of Earth in its orbit, we quickly caught up to it as it was crossing our orbit by Tuesday evening. Travelling at roughly 40,000 kilometres per hour, it quickly dove past the orbit of the Moon, at 384,400 km out, past our ring of geostationary satellites, roughly 30,000 km above the surface, and flew past the Earth only around 7,000 kilometres above our heads. According to Ron Baalke, of NASA's Jet Propulsion Laboratory, that was one of the closest 'near misses' in history. By comparison, asteroid 2012 DA14 - now with its permanent name 367943 Duende - came as close as 27,700 kilometres as it passed Earth on February 15, 2013. Coincidentally, earlier that morning, another previously-undiscovered asteroid that measured up to 20 metres wide made history when it exploded over Chelyabinsk, Russia.
Although the Chelyabinsk asteroid was likely the largest object that's hit our planet in the last decade or so, it definitely wasn't the only one. The B612 Foundation announced back in April that they had used data from the Comprehensive Nuclear Test-Ban Treaty Organization's infrasound network to plot out over two dozen large impacts (releasing energy equivalent of at least a 1 kiloton nuclear explosion) going back to the year 2000. This video shows their results:
The majority of these impacts when completely unnoticed, except for the records from the infrasound network. Another impact that didn't rate the video, but was also noteworthy, took place in the evening of January 1, 2014. Asteroid 2014 AA, the very first discovered this year, was detected just after the ball dropped, Eastern Standard Time, and by the end of the day it had burned up in our atmosphere, over the Atlantic Ocean northeast of South America.
What would have happened if 2014 LY21 hit us instead of giving us this close shave?
It probably would have gone unnoticed, like the majority of the ones in the video had, and estimated at around 5 metres wide, or roughly the size of a moving van, it wouldn't have survived the dive into our atmosphere to reach the ground. However, according to Baalke's reply to someone over Twitter: "If it had entered the atmosphere over a populated area, it would have been visible as a very bright fireball with sonic booms."