Two galaxies appear to be colliding in Hubble image, but are not

Two galaxies that appear to be colliding are actually tens of millions of light-years apart.
(NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and W. Keel (University of Alabama)

Two distant galaxies that appear to be colliding in an image captured by the Hubble Space Telescope actually are not, researchers said this week; the apparent collision is simply a trick of perspective that occurs because both galaxies are in the same direction from Earth. They are actually tens of millions of light-years apart, about 10 times the distance between our own Milky Way galaxy and the nearby Andromeda galaxy.

The object was originally designated NGC 3314 when lower-resolution imaging suggested it was only one galaxy. It is about 140 million light-years from Earth. The front galaxy, oriented from upper left to lower right, is now designated NGC 3314A, while the rear one is called NGC 3314B. Their motions indicate that each is relatively undisturbed and that they are moving in markedly different directions, and thus not on a collision course. NGC 3314A appears to have a slightly warped shape due to an encounter with another nearby galaxy, but astronomers believe that encounter to have been with the large spiral galaxy NGC 3312, not visible in the image.

Because of the alignment, NGC 3314B dust lanes appear lighter than those of the front galaxy; that is because they are illuminated by the bright stars in the front galaxy. The dust in the front galaxy, in contrast, appears darker because it is backlighted by stars in NGC 3314B.

The image was produced by combining several hour-long exposures in blue and red light. The Hubble telescope is operated jointly by NASA and the European Space Agency.