The curious case of NGC 660

Unique in its kind, NGC 660 is a galaxy located 40 million light years from Earth, visible in the constellation Pisces.

It is quite immediate to understand what makes this galaxy unique: it is the external structure that surrounds its central body.

These objects characterized by an external ring of gas and stars rotating around the poles of the central nucleus are called polar-ring galaxies. 

Actually, the outer ring of NGC 660 is not exactly around the poles of the galaxy, but inclined by 45 Astronomers speculate that these rings form as a result of a collision between two galaxies. In the case of NGC 660, the two galaxies involved would be the spheroidal one that today forms the center of the system and a spiral galaxy that has formed the outer ring. As evidence of the collision, which is estimated to have occurred a billion years ago, the pink star-forming regions visible in the ring remained, which would have been triggered by tidal forces generated during the collision between the two objects.

Credit: NASA - Gemini Observatory, AURA.