The discovery of gravity waves in early 2013 was huge news around the world ... and so was the retraction after the scientists realized they'd made a mistake. This is a dramatic human story of brave scientists and big science in action at the South Pole.
Active galaxies pour out lots of energy, due to their central supermassive black holes gobbling down matter. Galaxies tend not to be loners, but instead exist in smaller groups and larger clusters. Our Milky Way is part of the Local Group, and will one day collide with the Andromeda galaxy. Clusters of galaxies also clump together to form superclusters, the largest structures in the Universe. In total, there are hundreds of billions of galaxies in the Universe.
As we approach the end of Crash Course Astronomy, it’s time now to acknowledge that our Universe’s days are numbered. Stars will die out after a few trillion years, protons will decay and matter will dissolve after a thousand trillion trillion trillion years, black holes will evaporate after 10^92 years, and then all will be dark. But there is still hope that a new Universe will be born from it.
An exploration of the dramatic fate of our future descendants, the technology they'll need to survive the end of this world billions of years from now and our options for colonizing and starting again on a new planet somewhere far from Earth.
Last week we covered multiple star systems, but what if we added thousands or even millions of stars to the mix? A star cluster. There are different kinds of clusters, though. Open clusters contain hundreds or thousands of stars held together by gravity. They’re young, and evaporate over time, their stars let loose to roam space freely. Globular clusters, on the other hand, are larger, have hundreds of thousands of stars, and are more spherical. They’re very old, a significant fraction of the age of the Universe itself, and that means their stars have less heavy elements in them, are redder, and probably don’t have planets (though we’re not really sure).