NASA releases Hubble image of galaxies 'twinned' by gravity

NASA has released an image from the Hubble space telescope of twin galaxies astronomers say are close enough to each other to be bound together by gravity. The two very similar galaxies, PGC 9074 and PGC 9071, are probably only just beginning to interact gravitationally, NASA said in a release Tuesday. No gravitational disturbance can yet be seen in the image, the space agency said. Both galaxies are similar in configuration and about the same size. PGC 9074 shows a bright bulge and two spiral arms tightly wound around the nucleus, features classifying it as a type Sa galaxy. PGC 9071 is a type Sb galaxy with a fainter bulge and a slightly different structure to its arms, with their coils are further apart. Gradually, NASA said, these two neighbors will attract each other, increasing the process of star formation in both and creating gravitational tidal forces that will throw out long tails of stars and gas. After hundreds of millions of years the structures of the interacting galaxies will merge together into a new, larger galaxy, astronomers said.