AUSTRALIA — Here’s some astronomical news that surely would have put a smile on Johnny Cash’s face. Australian researchers have snapped an image of a galaxy as it existed 11 billion years ago, and it looks like a burning ring of fire.
This burning galaxy has roughly the same mass as the Milky Way, but is circular with a hole in the middle. Beyond just looking cool, these images are very significant; this galaxy’s discovery and appearance calls into question current accepted theories regarding how and when galactic structures came to be and how they evolved.
“It is a very curious object that we’ve never seen before,” says lead researcher Dr Tiantian Yuan, from Australia’s ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), in a release. “It looks strange and familiar at the same time.”
If you were thinking about the ring of fire galaxy as your next vacation destination, it’s probably a bit too far for Earth tourists; technically named R5519, the galaxy is 11 billion light years away from our solar system. The hole at the center of the galaxy gives “massive” a new definition. The gap is two billion times longer than between Earth and the Sun.
“It is making stars at a rate 50 times greater than the Milky Way,” Dr. Yuan adds. “Most of that activity is taking place on its ring – so it truly is a ring of fire.”
This discovery wasn’t all Australian, colleagues from the United States, Denmark, Canada, and Belgium all collaborated with Dr. Yuan on this project. Using data gathered by the WM Keck Observatory in Hawaii, in conjunction with images taken by NASA’s Hubble Space Telescope, they were able to find and identify the new galaxy.
R5519 is the first ever “collisional ring galaxy” to be discovered in the early universe.
For reference, there are two types of ring galaxies. More traditional, or common, ring galaxies form due to internal processes. Collisional galaxies, however, form because of “immense and violent” collisions with other galaxies.
In Earth’s nearby, “local” universe, collisional galaxies are 1,000 times more rare than internally created galaxies. Interestingly, since these new images of R5519 are believed to be from roughly 10.8 billion years ago (only three billion years after the big bang!), they indicate that collisional ring galaxies have always been very rare.
ASTRO 3D co-author, Dr Ahmed Elagali, believes that studying R5519 extensively will reveal when spiral galaxies first started developing.
“Further, constraining the number density of ring galaxies through cosmic time can also be used to put constraints on the assembly and evolution of local-like galaxy groups,” he says.
This ring of fire may also help us understand how the Milky Way galaxy was formed as well.
“The collisional formation of ring galaxies requires a thin disk to be present in the ‘victim’ galaxy before the collision occurs. The thin disk is the defining component of spiral galaxies: before it assembled, the galaxies were in a disorderly state, not yet recognizable as spiral galaxies.” adds study-co-author Kenneth Freeman, a professor at the Australian National University.
“In the case of this ring galaxy, we are looking back into the early universe by 11 billion years, into a time when thin disks were only just assembling. For comparison, the thin disk of our Milky Way began to come together only about nine billion years ago. This discovery is an indication that disk assembly in spiral galaxies occurred over a more extended period than previously thought,” he concludes.
The study is published in Nature Astronomy.