Astronomers have gathered information on the mix spiral, and elliptical, and oddball galaxies in two broad epochs to help tell the story of galaxy evolution
Credit: NASA, ESA, Sloan Digital Sky Survey, R. Delgado-Serrano and F. Hammer (Observatoire de Paris)
The past six billion years of the universe's 13.8-billion-year history may have been more exciting than people thought.
If an international team of astronomers is correct, galaxy collisions and mergers happened far more frequently during that period than previous research has indicated.
The team, led by Paris Observatory astronomer Francois Hammer, found that 6 billion years ago, the universe contained far more "peculiar" galaxy shapes than appear in more recent times. In effect, the population of these oddballs declined at the same time the proportion of spiral galaxies like the Milky Way increased significantly.
The farther out in space you look, the older the objects are, because light travels at a constant speed. The team based its results on images of 148 galaxies whose distances correspond to the universe as it was about 6 billion years ago. And the group examined images of 116 local galaxies. The images the astronomers used to came from the Sloan Digital Sky Survey and NASA's Great Observatories Origins Deep Survey.