ELEANOR HALL: Over the last two days, police and news organisations in South Australia and western Victoria have been inundated with reports of mysterious lights in the night sky.

Some have described a fireball shooting across the horizon just before sunset, while callers in north-west Victoria have reported seeing a bright object flying across the sky.

The Astronomical Society of South Australia's Dr Tony Beresford has told Nance Haxton that while the sightings have sparked some UFO speculation, the cosmic mystery is most likely a meteor.

ELEANOR HALL: Over the last two days, police and news organisations in South Australia and western Victoria have been inundated with reports of mysterious lights in the night sky.

Some have described a fireball shooting across the horizon just before sunset, while callers in north-west Victoria have reported seeing a bright object flying across the sky.

The Astronomical Society of South Australia's Dr Tony Beresford has told Nance Haxton that while the sightings have sparked some UFO speculation, the cosmic mystery is most likely a meteor.

TONY BERESFORD: It was just one particular meteor which was widely observed. It was observed from around the metropolitan area to, I suspect, over in the border regions of Victoria and New South Wales.

NANCE HAXTON: And how do we know that it was a meteor?

TONY BERESFORD: Well, it was a short time, it was moving quite fast, faster than a satellite would've and there were no satellites due to come in.

NANCE HAXTON: And are there any reports of what happened to that meteor? I mean, does it burn up before landing or...

TONY BERESFORD: This one almost certainly did. It's... in fact, I have several reports which indicated at the end it more or less exploded.

NANCE HAXTON: How common is it for meteors such as this to be seen so brightly and be reported by people?

TONY BERESFORD: Well, about once a year or so, maybe twice.

NANCE HAXTON: So meteors are really falling from the sky all the time, it's just sometimes we see them?

TONY BERESFORD: Some, yes. We're in a cosmic shooting gallery. There are several moderately recent craters in the Australian continent, but the most recent appreciable-sized one is of course the very famous meteor crater in Arizona, only about 50,000 years ago.

NANCE HAXTON: 50,000 years ago? So hopefully our number's not coming up for a while yet?

TONY BERESFORD: Well, you don't... you never know. I'm one of these people who think we should do proper surveys for an asteroid that could possibly impact the earth, because we... if we did find one then we could probably divert it enough. You don't have to change its orbit very much.

The Australian Government doesn't believe in it, but the Americans are spending money employing two people up at Siding Spring looking for it.

NANCE HAXTON: You think that the risk of an asteroid hitting earth is enough that Australia should really look at taking more note of the risk?

TONY BERESFORD: Yes, yes they should. The risk is very small, but the number... the possible global consequences are enormous.

ELEANOR HALL: That's the Astronomical Society of South Australia's Dr Tony Beresford speaking to Nance Haxton.