Ring Galaxy Zw II 28: Galaxy With the Hole in the Middle

Galaxy Zw II 28 possesses a mysterious ring shape. 

Researchers believe ring galaxies form when one galaxy slices through the disc of another, larger, one, though without much destruction as might be expected, as galaxies mostly contain empty space. 

This disruption should redistribute the material in both galaxies to form a dense central core, encircled by bright stars, iintensely forming new stars in the outer ring. 

The pink and purple loop of Zw II 28 does not represent a typical ring galaxy due to its lack of a visible central companion. 

However, a companion may lurk just inside the ring. Image released March 11, 2013.

Credit: ESA/Hubble & NASA, Acknowledgement: Judy Schmidt

When Galaxies Collide: Middle Merger

The galaxies seen here are caught mid-merger.

The bodies of the two parent galaxies have more or less fused but two independent central nuclei can still be seen in the image.

The collision is thought to have begun approximately 300 million years ago.

This object, known as NGC 520, is one of the brightest galaxy pairs on the sky, and is located about 100 million light-years away toward the constellation Pisces.

Image: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and B. Whitmore (STScI)