NGC 7252

"NGC 7252 (Arp 226) is a peculiar galaxy resulting from an interaction between two galaxies that started a billion years ago. It is located 220 million light years away in the constellation Aquarius. It is also called Atoms for Peace Galaxy, a nickname which comes from its loop-like structure, made of stars, that resembles a classic diagram of an electron orbiting an atomic nucleus.

The central region of the galaxy is home to hundreds of massive, ultra-luminous clusters of young stars that appear as bluish knots of light. These young clusters were created in the suspected galaxy merger, that pushed gases into these regions and caused a burst of star formation.

The most conspicuous of them is one known as W3, which has a mass of around 8 billions solar masses . This object, also the most luminous super star cluster known to date, has properties more similar to an ultra-compact dwarf galaxy and differs only from those galaxies because of its age (300–500 million years).

A pinwheel-shaped disk, rotating in a direction opposite to that of the galaxy, is found deep inside NGC 7252: it resembles a face-on spiral galaxy, yet it is only 10,000 light years across. It is believed that this pinwheel-shaped structure is a remnant of a collision between two galaxies. Within a few billion years, NGC 7252 will look like an elliptical galaxy with a small inner disk due to the exhaustion of the gases in the galaxy." (Wikipedia)