Astronomers have discovered an extremely rare doughnut-shaped galaxy that has been described as a “cosmic ring of fire”. Locate d approximately 11 billion light-years away from Earth, R5519 is about the same mass as our own Milky Way galaxy. What’s so incredibly strange about R5519 is that studies have indicated that it could possibly be a collisional ring galaxy and if that’s true, it would be the first one that’s ever been discovered in the early Universe.
A team of researchers from the United States, Canada, Denmark, Belgium, and Australia studied spectroscopic data of the galaxy from the WM Keck Observatory located in Hawaii and NASA’s Hubble Space Telescope. (A couple of pictures of R5519 can be seen here.)
Lead researcher Tiantian Yuan who is from Australia’s ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) described the galaxy as being a “very curious object” and that it “looks strange and familiar at the same time”.
The hole in the middle of the R5519 galaxy is so huge that its diameter measures about two billion times further than Earth is to our sun. And it’s currently quite active as stars are being created at a rate of 50 times faster than our own Milky Way galaxy. “Most of that activity is taking place on its ring, so it truly is a ring of fire,” Yuan said.
In a paper that was published in the journal Nature Astronomy, the researchers wrote in part, “Contrary to previous predictions, this work suggests that massive collisional rings were as rare 11 Gyr ago as they are today,” adding, “Our discovery offers a unique pathway for studying density waves in young galaxies, as well as constraining the cosmic evolution of spiral disks and galaxy groups.”
Astronomers have identified two types of ring galaxies – one where the hole was formed by internal processes which is the most common type; and the very rare occurrence when one galaxy has a violent collision with another one (called collisional galaxies).
Kenneth Freeman, who is from the Australian National University and is one of the co-authors of the study, explained this further, “The collisional formation of ring galaxies requires a thin disc to be present in the victim galaxy before the collision occurs,” adding, “The thin disc is the defining component of spiral galaxies: before it assembled, the galaxies were in a disorderly state, not yet recognizable as spiral galaxies.”
He went on to explain, “In the case of this ring galaxy, we are looking back into the early Universe by 11 billion years, into a time when thin discs were only just assembling. For comparison, the thin disc of our Milky Way began to come together only about nine billion years ago.” “This discovery is an indication that disc assembly in spiral galaxies occurred over a more extended period than previously thought.”
I wonder if this is what Johnny Cash had in mind when he was singing his hit tune, “Ring of Fire”.