Collisions between galaxies are relatively commonplace — such collisions are thought to be crucial to the eventual creation of supermassive black holes, and our own Milky Way is scheduled to merge with nearby Andromeda Galaxy in about four billion years.
But because galactic collisions take place over such an unfathomably long period of time, it's difficult to really see the visual evidence of this gargantuan cosmic phenomenon. That's why this Hubble telescope photo of galaxy NGC 6745 is so fascinating, as it shows a galaxy distorted out of its normal shape in the aftermath of a collision with a smaller galaxy, which is now moving away from it. Here's how NASA describes what's going on in this cosmic vista:
NGC 6745 actually shows the results of two galaxies that have been colliding for only hundreds of millions of years. Just off the above digitally sharpened photograph to the lower right is the smaller galaxy, moving away. The larger galaxy, pictured here, used to be a spiral galaxy but now is damaged and appears peculiar. Gravity has distorted the shapes of the galaxies. Although it is likely that no stars in the two galaxies directly collided, the gas, dust, and ambient magnetic fields do interact directly. In fact, a knot of gas pulled off the larger galaxy on the lower right has now begun to form stars. NGC 6745 spans about 80 thousand light-years across and is located about 200 million light-years away.
For an ultra-high-resolution image of NGC 6745, check out NASA's Astronomy Photo of the Day.
Image credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration .