Scientists didn't see car-size asteroid that made closest fly-by on record until after it passed Earth

TORONTO -- Scientists say they did not detect a car-size asteroid that flew within 3,000 kilometres of Earth on the weekend until hours after it had passed by.

The asteroid reportedly flew over the Southern Hemisphere just after midnight EDT on Sunday, marking the closest fly-by of Earth on record, according to asteroid trackers and a catalog compiled by Sormano Astronomical Observatory in Italy.

According to NASA's database of near-Earth objects, the asteroid flew by at nearly 7,770 kilometres from the centre of Earth and could have been less than 2,950 kilometres above humans at its closest point to the planet.

Telescope observations suggest that the asteroid, dubbed 2020 QG, had a diameter of roughly three to six metres, making it somewhere between the size of a car and a pickup truck.

Asteroid 2020 QG, which also went by the identifier ZTF0DxQ before being formally logged into NASA's database, was not spotted until after the moment of its closest approach. The Palomar Observatory in California first detected the space rock about six hours after it flew by Earth.

However, experts say there is no reason to be concerned. Because of its size, the asteroid most likely would not have posed any danger to humans had it hit Earth, as it would have exploded upon entering the atmosphere.

NASA says the agency only knows about a fraction of near-Earth objects, as many do not cross any telescopes’ line of sight and can be blocked by the direction of the sun.

Potentially dangerous asteroids have managed to sneak up on scientists in the past.

A comparably sized asteroid known as ZLAF9B2 was spotted only eight hours before it hit Earth in June 2018. Only small fragments of the space rock made it to the ground in Africa, causing no reported damage or injuries.