Astronomers have discovered a rare type of galaxy 359 million light-years from Earth that came with a bit of a surprise.

This galaxy — with the rather unimpressive name of PGC 1000714 — is unlike any galaxy you might be familiar with. Instead of the more commonly known type with wide spiral arms, this is a rare galaxy and often referred to as a ring galaxy. All the ring galaxies discovered so far contain a ring around a bright, central core. However, this newly discovered object has two rings.

Researchers found this second faint ring while studying PGC 1000714. The outer ring is just 0.13 billion years old with a 5.5 billion year-old central core. But when examining the data collected, they found another faint, red ring around the centre. 

The most well-known type of ring galaxy is Hoag's Object, which lies 600 million light years from Earth.

Hoag's Object galaxy

A nearly perfect ring of hot, blue stars pinwheels around the yellow nucleus of an unusual galaxy known as Hoag's Object. This image from NASA's Hubble Space Telescope captures a face-on view of the galaxy's ring of stars, revealing more detail than any existing photo of this object. (NASA and The Hubble Heritage Team (STScI/AURA))

"Less than 0.1 per cent of all observed galaxies are Hoag-type galaxies," Burcin Mutlu-Pakdil, lead author of a paper on this work said in a statement.

Rings around galaxies are believed to be regions where stars formed due to the collision of gases. In the case of this new object, the different colours suggest that the stars formed at different times.

The scientists say that discovering such a new structure challenges current theories about the formation of the universe and illustrates that there is still much to learn.

The study was published in the Monthly Notices of the Royal Astronomical Society.