By Sarah Romero
Astrophysicists claim they have never seen one like this before. It is approximately 359 million light-years distant from Earth and is unlike anything seen before. According to scientists from the University of Minnesota Duluth and the North Carolina Museum of Natural Sciences (USA), it would be a Hoag-type galaxy with a well-defined nucleus surrounded by -in this case- two circular rings instead of one.
"Less than 0.1% of all observed galaxies are Hoag-type galaxies," says Burcin Mutlu-Pakdil, lead author of a paper. The fact is that Hoag-type galaxies are almost perfect rings of young blue stars surrounding a nucleus of older yellow stars, with nothing to visibly connect them. Most of them are disk-shaped like our own galaxy, the Milky Way.
Astrophysicists examined multi-wave images of this entire galaxy using a large-diameter telescope in the mountains of Chile. Thanks to them they were able to determine the ages of the two main features of the galaxy, the outer ring and the central body. Thus, they observed a young blue ring (1,300 million years old), surrounding a red and older nucleus (5,500 million years old). But that was not all. Astronomers discovered evidence of a second inner ring around the central body.
"We have observed galaxies with a blue ring around a central red body before, the best known of these being the Hoag object. However, the unique feature of this galaxy is what appears to be an ancient inner diffuse red ring," he says. Patrick Treuthardt, co-author of the study.
"Whenever we find a unique or strange object to study, it challenges our current theories and assumptions about how the Universe works; it usually tells us that we still have a lot to learn," Treuthardt says.
The study has been published in the Monthly Notices of the Royal Astronomical Society.