The cosmologist at the end of the universePosted: February 3, 2011
Sit down, put on some depressing music (anything in my CD collection should do the trick) and allow me to take on the role of Private Frazer to tell you the Galaxy is doomed, doomed to losing it’s beautiful structure, doomed to being seemingly alone in the the universe. Yet even in this bleak environment the intrepid cosmologist can still strive to untangle the mysteries of the universe.
You might have heard that the universe is expanding. You may also know that from various lines of evidence that this expansion is speeding up. In fact the expansion could be growing so fast that in a trillion years the galaxies we see today will be so far away that light from them will take longer than the age of the Universe to reach us. In the long term all we will see is our own Galaxy. When I say our own Galaxy, it won’t be the pretty spiral illustration we see in the classic pictures, the Galaxy is headed for a train wreck.
Our Galaxy is slowly falling towards its neighbour Andromeda. It seems likely that in a few billion years the two galaxies will collide. This will cause the beautiful spiral structures to be ripped apart with the galaxies merging into a large blob like structure. Here’s a nice video showing what might happen.
So we’re in a big blob of a galaxy with no extragalactic sources to observe. I know what you are thinking, what about all the unemployed cosmologists in the far future? But don’t start a collection for the hardship fund just yet, luckily a new paper by a researcher at Harvard has come up with a way for astronomers in the far future to measure the parameters of the universe.
Our Galaxy has a huge black hole in the centre. When stars get too close to this they can get a huge kick in their velocity leading to them being ejected from the Galaxy. Even once the collision has formed Milkomeda (which sounds like an Italian dairy) these expulsions will continue to happen. In the distant future these will be the only extragalactic objects visible. The paper examines what the distribution of these stars will look like and determines that future astronomers could measure the acceleration of the universe using their recession velocities.
So even when all we can see of the universe will be our own Galaxy, we will still be able to measure one of the fundamental parameters of the universe.
Abraham Loeb (2011). On the Importance of Hypervelocity Stars for the Long-Term Future of
Cosmology ApJ arXiv: 1102.0007v1