A leading Melbourne astronomer says an object that lit up eastern Australian skies last night was not a meteor but instead a piece of space junk.

Pilots, air traffic controllers and members of the public spotted the bright light streaking across the sky about 10:00pm.

But Melbourne Planetarium curator Dr Tanya Hill says it was space junk, not a meteor.

"What was really interesting about it was it was so bright and observers have reported being able to see it for more than 10 seconds or so," she said.

"That tells us that it was something probably more out of the ordinary than just a small meteor.

"This is ... what you would call an artificial meteor, caused by material we may well have sent up in space."

Dr Hill says NASA tracks more than 500,000 pieces of space junk that measure greater than the size of a marble.

"Narrowing down what it might be is actually going to be a really tough ask," she said.

"Probably about once a day a piece of space junk ... flies through our atmosphere. We were just lucky to be able to witness it last night."

Airservices Australia spokesman Paul Sadler says colleagues who saw the activity last night described it as a spectacular sight.

"Some controllers are looking at radar screens but those controllers looking out to the runways certainly could see it," he said.

"It was reported from northern NSW down to Hobart and it was in the north-western part of the sky.

"I'd be suggesting it was sort of somewhere over NSW."

Mr Sadler says some people who spotted the light confused the unusual sight for an aircraft in trouble.

"It's understood there were a number of triple-zero calls to emergency services possibly reporting a plane in trouble but that certainly wasn't the case," he said.

"A number of pilots flying in that airspace reported it to ... air traffic controllers [and said] it was just a spectacular sight."

Did you spot the unusual light? Tweet us your photos at @abcnews or email us at yourpics@abc.net.au.