Farmer James Stirton found the odd-shaped ball last year on his 40,000 hectare property, about 800 kilometres (500 miles) west of the northern Queensland state capital of Brisbane.
But Stirton only started inquiring into what the ball of metal really was, and where it had come from, in the past week.
"I was riding out to check some cattle, and I came around the corner and there it was in a paddock," Stirton told Reuters on Friday.
"I know a lot of about sheep and cattle but I don't know much about satellites. But I would say it is a fuel cell off some stage of a rocket."
He said the object was hollow, and covered in a carbon-fibre material. He has contacted some U.S.-based aerospace companies to try to find out what the object really is.
Sydney's Powerhouse Museum said it was not uncommon for people to find spacejunk in remote areas of Australia.
In 1979, large parts of the Skylab space station fell to earth near a tiny outback town in Australia's west. A local council sent NASA a ticket for littering and then United States President Jimmy Carter rang a local motel to apologise. (Reuters)