Collision course

The majority of objects we see in the cosmos are galaxies (made up of stars, planets, dust, and gas), and it’s not uncommon for one galaxy to eventually cross paths with another. In fact, galaxies frequently circle each other for billions of years, their gravitational attractions pulling them closer and closer until they collide.

When these cosmic collisions occur, friction between gas and dust inside each galaxy elevates temperatures, and interstellar material combines into huge molecular clouds. With all of this agitation, starbursts – exceptionally high rates of star formation – can even form.

The image shows a formation in which one galaxy presents a single, bright nucleus and an outer structure that consists of a one-sided extension of inner arms, with a tidal tail going in the opposite direction. The tail formed from material pulled out by gravitational forces during the merge.

The object is an ultra luminous, infrared galaxy, which emits a tremendous amount of light at infrared wavelengths. Scientists connect this to intense star formation, caused by a collision between the two galaxies. In this way, collisions and mergers drive the evolution of galaxies – and shape the history of our universe.

- Amber Harmon