Rare doughnut-shaped galaxy — a ‘cosmic ring of fire' — is making baby stars 50 times faster than the Milky Way

  • Astronomers have spotted a ‘cosmic ring of fire11 billion light-years away from Earth.
  • Its making baby stars worth 80 solar masses’ every year — that’s 50 times as fast as the Milky Way.
  • The doughnut-shaped galaxy could also hold the key to finding how spiral galaxies, like the Milky Way, get their shape over billions of years.
Astronomers have spotted a ‘cosmic ring of fire’ making stars 50 times faster than the Milky Way — even though its mass is roughly the same size. Unlike other galaxies, which are shaped like spirals or blobs, R5519 looks like a giant galactic doughnut complete with a massive hole punched right through its centre.

“It’s a very curious object that we’ve never seen before,” said Tiantian Yuan, lead author of the study published in Nature Astronomy. “Most of that activity is taking place on its ring — so it truly is a ring of fire,” he added.

The hole at its centre is as massive as two billion times the distance between the Sun and Earth. If you’re familiar with the first black hole ever captured on film, the Messier 87 — the hole is three million times bigger.


An artist’s impression of the ring galaxyJames Josephides, Swinburne Astronomy Productions

It’s surrounding ring is giving birth to stars worth 80 solar masses’ every year, which could mean that another galaxy is still punching its way through R5519. As it passes through, the density waves as pushing and condensing gas and dust in the galaxy. This could be the trigger letting the gravitational collapse turn those clumps of dust and gas into baby stars, according to the study.

Scars of battles and collisions with other galaxies
There are two kinds of ring galaxies. Ones that form because of internal processes, and others, like the ‘cosmic ring of fire’, that form because of repeated collisions with other galaxies. These collisions aren’t just fly-bys or gentle nudges — they’re immense and violent encounters that create the gaping hole at the centre.

According to Yuan, these rings created due to battle scars are 1000 times rarer in the ‘local’ universe than ones created due to internal disruptions. The core is essentially ripped away as another galaxy passes through its heart.

<sup></sup>A composite image of the ring galaxy R5519 compiled from single-colour images taken by the Hubble Space TelescopeTiantian Yuan/Hubble Space Telescope

The secret to how the Milky Way formed
“The collisional formation of ring galaxies requires a thin disk to be present in the ‘victim’ galaxy before the collision occurs,” explains co-author Kenneth Freeman. And, this could be the secret to understanding how spiral galaxies like the Milky Way come into existence in the first place.

“The thin disk is the defining component of spiral galaxies. Before it assembled, the galaxies were in a disorderly state, not yet recognisable as spiral galaxies,” he explains.


The Milky Way in stars and dustSerge Brunier/APOD/NASA

Dubbed R5519, the galaxy is nearly 11 billion light-years away from our own Solar System. In scientific terms, this means that we’re looking 11 billion years into the past. In comparison, the Milky Way only began to come together nine billion years ago. “This discovery is an indication that disk assembly in spiral galaxies occurred over a more extended period than previously through,” said Freeman.

Yuan and his team used spectroscopic data from the WM Keck Observatory in Hawaii combined with images recorded using the National Aeronautics and Space Administration’s (NASA) Hubble Space Telescope to identify the ‘cosmic ring of fire’.

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