It took just a couple of hours using data available on the internet for University of Sydney scientists to discover that the Milky Way is twice as wide as previously thought.

Astrophysicist Professor Bryan Gaensler led a team that has found that our galaxy - a flattened spiral about 100,000 light years across - is 12,000 light years thick, not the 6,000 light years that had been previously thought.

Proving not all science requires big, expensive apparatus, Professor Gaensler and colleagues, Dr Greg Madsen, Dr Shami Chatterjee and PhD student Ann Mao, downloaded data from the internet and analysed it in a spreadsheet.

"We were tossing around ideas about the size of the Galaxy, and thought we had better check the standard numbers that everyone uses. It took us just a few hours to calculate this for ourselves. We thought we had to be wrong, so we checked and rechecked and couldn't find any mistakes."