What is causing the galaxy in the lower right to create a ring of stars around it ?
It is thought that a colliding galaxy moved through this galaxy, and as it did it sent out a compression wave which has brought the dust and gas together creating dense nebula that stars can then form from. As the ring has raced outwards, so has the star formation, but in this instance, the galaxy has also stretched outwards a little as the gravity balance between this and the colliding galaxy warp the structure.
The once spiral galaxy is 300 million light years from Earth in the constellation of Volans.
Galaxy mergers play a critical role in driving galaxy evolution, especially by transforming galaxy morphology, redistributing the gas around
At redshift z = 1.14, this system reveals two ring galaxies, each around 26,000 light‑years across, formed through an almost perfect, head‑on collision that has caused powerful shockwaves to compress gas into star‑forming rings.
The JWST NIRCam imaging shows two near‑identical rings, with bright central regions making them look like big owl eyes, and a starburst “beak” where they overlap. These rings originated roughly 38 million years ago, when one galaxy plunged through the other in a near‑central impact, sending ripples of star formation outward.
Both galaxies host active galactic nuclei (AGN). JWST’s grism spectroscopy detected broad hydrogen Paschen emission from each core, confirming two AGN.
These black holes have estimated masses of ~10⁸ M☉ each and are separated by roughly 10 kpc, a bona fide binary AGN. Chandra X‑ray and radio data from VLA further back up the AGN presence, including the detection of high‑ionization emission lines like [Ne V].
Where the rings intersect, what astronomers call the “beak”, a fiery starburst is underway. ALMA has mapped a substantial reservoir of cold molecular gas there, while JWST shows intense nebular line emission and VLA reveals a radio hotspot aligned with this region.
A relativistic jet from the NW AGN appears to slam into the beak, further shocking local gas and triggering efficient star formation, with a rapid gas depletion timescale. This is a textbook example of shock‑induced star formation in action.
Extreme rarity: Collisional ring galaxies require precise, head‑on collisions, seeing two, simultaneous rings at high redshift is practically unheard of.
Fast stellar assembly: The combination of merger-driven shocks and jet feedback makes this system a compelling case for how galaxies rapidly grow during the earlier universe.
Insight into cosmic evolution: With dual AGN, cold gas, and jet-driven star formation all in one frame, the Cosmic Owl serves as a rare laboratory for understanding how galaxies and black holes evolve together.
The Cosmic Owl at z = 1.14 is a spectacular cosmic event: two galaxies locked in a head‑on collision, each forming a glowing ring and housing a supermassive black hole.
Their merger has lit up a blast of star formation at the collision front, fueled both by gravitational upheaval and a targeted AGN jet. It beautifully illustrates the dramatic mechanisms that drive galaxy formation in the early universe, caught in the act, and looking uncannily like a giant glowing owl in JWST’s eyes.
Reading about Hoag's Object got me into ring galaxies...
So, suffer the consequences. /j
If you read about galaxies, spirals (like our Milky Way), ellipticals (like M87) & irregulars are all more common than ring galaxies.
Galaxies are collections of matter, including plasmas, gas, dust, planets & of course, stars. In the galactic center, there is always a supermassive black hole.
When you look at a ring galaxy, there are 3 features that stick out as unusual among galaxies.
A central core, that’s low in gas & consists primarily of older stars, meaning very little recent star-formation in that region
A gap around that central region: very low density, with almost no stars, no light & very little gas or neutral matter.
A bright, luminous ring that surrounds the central core but is much bluer in color than the core itself, indicating that the stars within the ring formed much more recently & are dominated by hot, short-lived, blue colored stars.
How do ring galaxies form?
Even though the universe is big, it is inevitable that galaxies will collide. If colliding galaxies don’t have enough momentum to move past each other, they can merge to form a single larger galaxy. Which is what will happen with Milky Way and Andromeda.
A merged galaxy can look very different from the two that created it. For example, if a spiral and elliptical merge, the result could be an irregular galaxy.
If a large galaxy merges with a smaller one, gravitational ripples most likely will disturb both galaxies, throwing gas, dust & stars outward. The result can be a ring of material at the edge of the new galaxy that is full of the material needed for star formation – a ring galaxy.
This Hubble Space Telescope image of Mayall’s object, also known as ARP 148, shows two galaxies in the process of collision.
As one galaxy punches through the center of the other, stars form in both galaxies, but the one that got "punched" is having its gas propagate outward in waves, triggering new star formation on its way toward creating an overall ring-like shape.
(While some material is thrown outward, other materials can stream toward the core and fuel the galaxy’s central black hole, resulting in an active galactic nucleus.)
The rim of ring galaxy AM 0644-741, imaged by the Hubble Space Telescope, spans 150,000 light years.
Credit: NASA, ESA, Hubble, HLA; Processing: Jonathan Lodge
Another example of a ring galaxy is the Cartwheel galaxy.
On the right, you can not only see the dense, older core of a pre-existing gas-rich spiral galaxy surrounded by a bright blue ring of hot, young stars, but also a series of filaments between the core and the ring.
Those filaments themselves are dotted with blue and white stars, although of a much lower brightness than either the main core or the ring itself.
An article published in the "Astrophysical Journal" describes the detection of a series of X-ray sources in the ring of the galaxy AM 0644-741. A team of researchers led by Anna Wolter from INAF-Osservatorio Astronomico di Brera, Italy, used observations from NASA's Chandra X-ray Observatory to discover those ultraluminous sources concluding that the ring containing them consists of binary systems that include black holes or neutron stars and that the ring formed following a collision between galaxies.
