NASA and other space agencies around the world put considerable effort into discovering and tracking all near-Earth asteroids. Near-Earth is a name that makes many people feel like these asteroids are extremely close to our planet, but they are typically millions of miles away. While that’s near on a cosmic scale, typically near-Earth asteroids offer no real threat to our planet.
Asteroid 2021 TJ15 made the closest approach to the planet when it flew by the Earth at a distance of 238,854 miles away. That’s the same distance the moon orbits away from Earth. The asteroid was relatively small, with a diameter of between 18 and 42 feet. Another asteroid is called Asteroid 2004 UE, which is estimated to be up to 1246 feet in size.
Its size makes approximately the same size as the Empire State Building. That asteroid will make its closest approach on November 13 at a distance of about 2.6 million miles from Earth. 2.6 million miles is equivalent to just over 11 times the distance of the moon from Earth. Asteroid 2004 UE is considered medium size.
Most of the asteroids considered near-Earth are small or medium-size, ranging from around 984 feet to 1968 feet in size. Near-Earth asteroids considered large can be up to 3280 feet or larger in size. Scientists tracking near-Earth asteroids point out that there are relatively few large asteroids near our planet.
The largest near-Earth asteroid is about 10 kilometers in size, but only one or two of that size exist. We know large asteroids have struck the Earth in the past, leading to the extinction of the dinosaurs. Over the last two decades of tracking near-Earth asteroids, only four that have been observed in space and then entered our atmosphere have been tracked. In those instances, scientists were able to predict where the meteorite impacted accurately, and teams were able to go out and collect them.