Asteroid 2021 UA1 Comes Within 3000 Kilometers of Earth, Undetected Until Just Before Approach
An asteroid roughly the size of a refrigerator, known as 2021 UA1, passed within a mere 3,000 kilometers of Earth without scientists being aware of its approach until moments before it passed by. This makes 2021 UA1 the third-closest asteroid to ever come near our planet.
On Sunday, the asteroid flew over Antarctica at an altitude higher than the International Space Station but lower than the orbit of most communication satellites. With a diameter of just two meters, it likely would have been burned up in Earth’s atmosphere if it had come any closer.
The surprise fly-by occurred because the asteroid was approaching from behind the Sun, making it undetectable from Earth until its closest approach, according to Tony Dunn, an astronomer and creator of the website Orbitsimulator. “The reason the planet’s fly-by was so surprising was because it was behind the sun, coming from the daytime sky, so it was undiscoverable prior to closest approach,” Dunn tweeted.