Henrietta Swan Leavitt they became an important part of the evidence that "spiral nebulae" are independent galaxies located far outside of our own Milky Way. Thus, Leavitt's discovery would forever change our picture of the universe, as it prompted Harlow Shapley to move our Sun from the center of the galaxy in the "Great Debate" and Edwin Hubble to move our galaxy from the center of the universe. Leavitt's discovery of a way to accurately measure distances on an inter-galactic scale, paved the way for modern astronomy's understanding of the structure and scale of the universe. The accomplishments of Edwin Hubble, the American
Atlas of Peculiar Galaxies formed between the two galaxies. Many of the other galaxies in this category are also connected by bridges. Like the spiral galaxies with high surface brightness companions, most of these spiral galaxies are clearly interacting systems. Tidal tails and bridges are visible in many of the images. These objects are very similar to the spiral galaxies with elliptical companions. All of the galaxies have features such as tidal tails and tidal bridges that have formed through gravitational interaction. Based on the description of these objects, it appears that Arp originally thought that the elliptical galaxies were pushing away spiral arms