Galaxies come in all shapes and sizes, but few are ring galaxies. Astronomers studying one of these objects on the other side of the universe have noted some startling properties. As with other ring galaxies, this one is not a result of internal processes driving stars apart. The team believes R5519 is the result of a cataclysmic collision in the early universe in which another object punched a hole through the middle of R5519.
This galaxy is a whopping 11 billion light-years away, meaning it’s also an artifact of the early universe. It shows a large ring-shaped perimeter with no discernable central bulge. The ring is about 42,400 light-years across, and the hole through its center is 17,612 light-years wide. By comparison, the Milky Way is between 150,000 and 200,000 light-years across.
Some ring galaxies studied in the past showed evidence of orbital resonance or accretion of material from other objects as the driving force behind the “ring.” However, orbital effects should only occur in barred galaxies, which R5519 is not. Likewise, accretion wouldn’t disrupt the core as seen in R5519. R5519’s unusual shape and origins could change the way scientists understand the formation of galaxies during the first few billion years after the Big Bang.
So, a collision seems possible simply by process of elimination. However, there’s additional evidence that R5519 had a violent past. The rate of star formation in the ring is extremely high — the team estimates that 80 solar masses of new stars are born each year in this region. That’s what the team refers to as a “cosmic ring of fire.” That could be a result of the gravitational turmoil of another galaxy passing through the center of R5519. The gravitational waves would propagate outward, condensing dust and gas into regions that promote the formation of new stars.
This offers an interesting chance to study galaxy formation in the early universe because disc-shaped galaxies were rare until just a few billion years ago. In the first few billion years, most galaxies were warped into irregular blobs, but you can’t have a ring galaxy unless it started as a disc. The discovery of R5519 suggests disc-shaped galaxies were not unheard of in the early universe, but a disc that became a ring is certainly something of note that warrants further study.
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