Large asteroid just grazes past Earth

A chunk of rock 30 metres across is hurtling across the southern skies of New Zealand on Thursday evening.

Asteroid 2012 TC4 is travelling at 25,000km/h and is at its closest point to Earth - but don't worry, it's going to miss us.

The house-sized TC4 was first discovered in 2012 and it's back for a repeat visit, which astronomy websites have been monitoring live.

TC4's flight path means it will be 43,500km away when it passes over the oceans south of New Zealand and Australia.

To put that into perspective, communications satellites orbit at 36,000km.

The asteroid is not far away from them and much closer than the moon - but it's unlikely to hit any space traffic.

"Both are tiny targets so the chance of any collision between it and any of the satellites is vanishingly small," astronomer Alan Gilmore told Newshub.

The world has felt the effects of small rocks hitting home before.

In 2014, the sonic boom of a meteor hit the Russian town of Chelyabinsk, blowing out windows. That space rock was smaller than the one above us now.

NASA says while TC4 isn't going to hit, it is useful to help test an Asteroid Warning System which relies on telescopes, including one in Hawaii.

The technology has found close encounters are a lot more common than previously thought.

"There are now tens of thousands of what are called 'near Earth objects' that are catalogued and being tracked," Mr Gilmore said.

But don't rush outside. TC4 may be close, but it's not close enough to see with the naked eye.