On Saturday, the 2023DZ2 will come within a third of the distance from the Earth to the Moon.

The asteroid, named 2023 DZ2, is estimated to be 40 to 70 metres (130 to 230 feet) wide, roughly the size of the Parthenon, and big enough to wipe out a large city if it hit our planet.

At 19:49 GMT on Saturday, it will come within a third of the distance from the Earth to the Moon, said Richard Moissl, the head of the ESA’s planetary defence office.

Though that is “very close”, there is nothing to worry about, he told AFP news agency.

Small asteroids fly past every day, but one of this size coming so close to Earth only happens about once every 10 years, he added.

The asteroid will pass 175,000km (109,000 miles) from Earth at a speed of 28,000 kilometres per hour (17,400 miles per hour). The Moon is roughly 385,000km (239,228 miles) away.

An observatory in La Palma, one of Spain’s Canary Islands, first spotted the asteroid on February 27.

Last week, the United Nations-endorsed International Asteroid Warning Network decided it would take advantage of the close look, carrying out a “rapid characterisation” of 2023 DZ2, Moissl said. That means astronomers around the world will analyse the asteroid with a range of instruments such as spectrometers and radars.

The goal is to find out just how much we can learn about such an asteroid in only a week, Moissl said. It will also serve as training for how the network “would react to a threat” possibly heading our way in the future, he added.

The asteroid will again swing past Earth in 2026, but poses no threat of impact for at least the next 100 years – which is how far out its trajectory has been calculated.