Milky way twice the size
Or more accurately the milky way is twice as thick as we previously supposed, 12,000 light years thick, rather than 6,000 light years. A light year is the distance it takes like to travel in a year. By comparison light can travel around the earth 7 times in one second. The galaxy is 100,000 light years across.
Astrophysicist Professor Bryan Gaensler, of the University of Sydney, led the team that made the discovery by sifting through our current data. 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,” they told the press.
“We used data from pulsars: stars that flash with a regular pulse,” Professor Gaensler explained. “As light from these pulsars travels to us, it interacts with electrons scattered between the stars (the Warm Ionised Medium, or WIM), which slows the light down. In particular, the longer (redder) wavelengths of the pulse slow down more than the shorter (bluer) wavelengths, so by seeing how far the red lags behind the blue we can calculate how much WIM the pulse has travelled through. If you know the distance to the pulsar accurately, then you can work out how dense the WIM is and where it stops - in other words where the Galaxy’s edge is. Of the thousands of pulsars known in and around our Galaxy, only about 60 have really well known distances. But to measure the thickness of the Milky Way we need to focus only on those that are sitting above or below the main part of the Galaxy; it turns out that pulsars embedded in the main disk of the Milky Way don’t give us useful information.”
http://www.usyd.edu.au/news/84.html?newsstoryid=2163
Image: Spiral Galaxy NGC 3949 - similar to the Milky Way. Image Credit: NASA, ESA and The Hubble Heritage Team (STScI/AURA). Acknowledgment: S. Smartt (The Queen’s University of Belfast).
