An artist's impression of the 2012 DA14 asteroid, which is going to miss Earth by only 28 000km.

Johannesburg - The closest asteroid to Earth yet recorded is going to swing past our planet on Friday evening.

And although it won’t hit us this time, it has the potential to wipe out any major city in South Africa if it were to collide with Earth.

The asteroid, named 2012 DA14, measures about 45m across and was discovered just a year ago, according to the outreach astronomer at the South African Astronomical Observatory, Nicola Loaring.

“It shows just how vulnerable we are,” she said.

The asteroid will pass us again in 2020, and although it was initially believed it would hit earth then, further research has shown that there won’t be any contact between the two bodies for at least the next 100 years.

The asteroid weighs about 130 000 tons, and is estimated to be travelling at about 28 800km/h.

“It’s basically coming through our backyard,” said Gary Els, the chairman of the Joburg branch of the Astronomical Society of Southern Africa (Assa).

He said the estimated distance of 28 000km between Earth and the asteroid at its closest point, at about 9.30pm, was considered a near-miss in astronomical terms.

“Should such an object ever hit us, it would cause a lot of damage. It would probably wipe out Joburg,” said Els.

He added that experts had documented 120 000 large asteroids and their trajectories through space and urged people not to panic. “Astronomers of the world are confident they know of 99 percent of the asteroids in the solar system and we are not in danger.”

However, if it hypothetically did crash into the sea along our shores near a city, a “monumentally large tsunami” would destroy that area too, according to the chairman of Assa’s Durban centre, Logan Govender.

Loaring said there were no plans to blow up asteroids on a collision course with Earth.

“If we know something is coming, we would warn the area where it is going to hit and organise things like evacuation and food supplies, like we do in disasters,” she noted.

The asteroid will pass through the ring of weather and communication satellites that orbit Earth, although a collision with one of these was also unlikely due to the vast expanse of space.

“As the asteroid passes through, there is a small chance (of a collision) that by an amazing coincidence and precisely at the same moment a satellite would be in its way,” said Govender.

It will be difficult to see the asteroid with the naked eye, but Els said Joburgers using binoculars or a small telescope at about 25 degrees to the horizon around the Southern Cross constellation might be able to spot it.

Loaring said it would probably be even lower in Cape Town, at around 10-15 degrees to the horizon and that people across the country would need to go to a relatively flat and open area to see it.

Even though it is close, it should look like a faint star moving slowly across the sky.

“Yes, (DA14) is the closest asteroid ever recorded, but that doesn’t mean there aren’t others that weren’t as close or even closer. Now we have the instruments to measure it,” said Govender.

In 1908, a meteor about the same size as 2012 DA14 crashed into a remote region of Siberia and generated a blast about 1 000 times more powerful than the Hiroshima atom bomb. - The Star