<img class="styles__noscript__2rw2y" src="https://s.w-x.co/util/image/w/in-asteroid_1_0.jpg?v=at&w=485&h=273" srcset="https://s.w-x.co/util/image/w/in-asteroid_1_0.jpg?v=at&w=485&h=273 400w, https://s.w-x.co/util/image/w/in-asteroid_1_0.jpg?v=ap&w=980&h=551 800w" > An illustration of an asteroid in space (Credits: NASA/JPL/Caltech)

An asteroid very narrowly missed the Earth last Thursday, and the scientists apparently had no clue about its approach. The large asteroid, about 100 metres in diameter, was nicknamed ‘city-killer’ due to the potential threat it posed.

According to reports , the rock, named Asteroid 2019 OK, passed within 73,000 kilometres of our planet—that’s one-fifth of the distance between the Earth and the moon!

Scientists say that its estimated diameter could range from 57 to 130 meters. The rock flew past the Earth at the speed of 24 kilometres per second on July 25, and was the biggest to fly at such close quarters to our planet this year, and possibly for many years.

Such was the propinquity that a person gazing at the right spot with a pair of binoculars could have caught sight of it in the night sky.

Despite the asteroid’s humongous size and proximity, it was entirely missed by the scientists. Therefore, its appearance out of nowhere resulted in a massive shock for the space community.

The space rock advanced towards Earth from the direction of the sun, which made it difficult to spot for the astronomers. Its speed and eccentric orbit further complicated the issue.

Telescopes began to notice the celestial body’s presence just two days before it soared past our planet. A confirmation regarding its identification was received merely 24 hours before the passage.

Had it collided with Earth, this city-killer asteroid would have generated 30 times the energy of the atomic blast at Hiroshima, say experts .

Apart from Asteroid 2019 OK, three other asteroids also sped past the Earth on the same day, but none were as huge, close and alarming as this near-miss rock.