An asteroid the size of a double-decker bus has passed by Earth and the moon in what astronomers consider a “near-miss”.
An asteroid made a surprise drive-by days after Christmas. [Image via National Geographic]
It was a nice little Christmas surprise from the universe. Astronomers at the Mount Lemmon Survey spotted the asteroid, named 2017 YZ4, on Christmas day. It was already quickly approaching Earth, making it quite a surprise for its discoverers. It sped past Earth on December 28 at a speed of almost 34,600 kilometers per hour, coming as close as a distance of 223,699 kilometers to Earth.
Now, that distance may seem like quite a lot, especially in Earth terms. However, even though a lot of space rocks pass by us on a regular basis, this one passed quite close in cosmic terms. 2017 YZ4 passed by Earth at a distance just over half the distance between the Earth and the moon. It came unusually close, and the alarming thing was that scientists were only able to discover it a few days before it whizzed by.
There are thousands of Near Earth Asteroids roaming around our planet.
Luckily, 2017 YZ4 wasn’t actually on a collision course with Earth. There was only a miniscule likelihood that the asteroid would shoot past the Earth’s atmosphere even though it did come awfully close. Thus, NASA has designated 2017 YZ4 a Near-Earth Asteroid, a designation given only to objects that come closer than 9.65 million kilometers to the Earth.
“As of December 25, there are 17,506 known Near-Earth Objects (NEOs), in orbits around the Sun that could come close to our planet; 17,400 are asteroids and 106 are comets,” says Lindley Johnson, Planetary Defense Officer at NASA’s Science Mission Directorate. “This year, we’ve discovered 1,996 Near-Earth Asteroids so far. There were 1887 such objects discovered in 2016 and 1,566 in 2015.”
NASA keeps track of all these NEOs so they can take the necessary measures in case a collision with Earth is possible. All objects that pass within of 7.4 million kilometers are considered to be hazardous. This means that we’re lucky that 2017 YZ4 wasn’t headed straight for us, especially since astronomers were only able to discover it a few days before it passed close to us. The late discovery would have meant that governments would not have had enough time to evacuate concerned areas if the asteroid had indeed been headed straight for Earth.
More asteroids are set to pass close by Earth in the future. [Image by Getty Images]
Still, if 2017 YZ4 had indeed hit Earth, it wouldn’t have spelled the demise of the human race. It’s likely to have caused damage, but not like the damage wrought by the asteroid thought to have killed off the dinosaurs. That asteroid, called the Chicxulub impactor, was probably 10 to 15 kilometers wide. 2017 YZ4 was just 6.88 to 15 meters wide, far smaller than the Chicxulub impactor.
2018 is also set to experience some near-misses with asteroids as well, with the asteroid 2017 DR109 set to pass close to Earth like 2017 YZ4 did. Astronomers have also calculated that on April 3, 2029, the asteroid 2004 MN4 will come far closer to Earth than 2017 YZ4. Even so, 2004 MN4 is unlikely to hit Earth.
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