A bright undergraduate student pointed out an article on a new type of galaxy called a "super spiral." Interestingly enough, a search through total of 800,000 galaxies to find out which are the brightest of them all revealed some surprises, 57 of them to be exact.
As background, I teach in my classes that there are four main types of galaxies: irregular-shaped ones, football-shaped ellipticals, relatively-flat spirals like the Milky Way, and the ones in between ellipticals and spirals called lenticulars. Of these, ellipticals are always thought to be the brightest and the largest in size. In fact, spiral galaxies are not physically supposed to get exceedingly-large. Astronomers are so sure of themselves on this point that it was considered hardly a point worthy of a test.
Even, so, when the test of which galaxy is the biggest was carried out and reported in the news just this past week, it emerged that spirals won the first place. Can spirals hold themselves together on very large scales? At 100,000 light years across the Milky Way is already enormous. Can spirals really get much larger than that? Well, of the 57 brightest galaxies identified in this most recent study, are all spiral galaxies 8-10 times bigger than the Milky Way.
Oh, astronomers already knew of their existence, but we did not bother to measure their distances as we simply thought them to be bigger because they were really close to us. It was only when the distances to these 57 galaxies was actually measured that it was realized that these objects are huge AND far away.
Although it will take time to determine how these galaxies fit into our galaxy zoo, it is thought that their large size may be a result of two or more galaxies merging together, and that the end product may be a lenticular galaxy.
What makes this discovery particularly interesting is that it was made using the Sloan Digital Sky Survey (SDSS), a public dataset. Anyone in the world, professional astronomer or not, could have made this discovery.