A group of worldwide researchers not too long ago found a galaxy with nine rings. They known as it a “serendipitous discovery” as a result of earlier ringed galaxies have solely displayed two or three rings at greatest.
Using the Hubble house telescope, the group confirmed the presence of eight rings, whereas information from the W.M. Keck Observatory in Hawaii confirmed the existence of the ninth ring.
This uncommon galaxy has been named LEDA 1313424 however its frequent title is extra memorable: the Bullseye Galaxy. The story of how its rings may have fashioned may render it extra memorable.
A skinny path of proof
When the researchers analysed the info from the house telescope and the observatory, they discovered indicators {that a} blue dwarf galaxy, positioned on the speedy centre-left in a picture, had handed via the centre of the Bullseye Galaxy about 50 million years in the past. They have stated this interplay gave the Bullseye Galaxy its distinctive form.
As proof of this interplay, the group reported a skinny path of fuel connecting the 2 galaxies regardless that they’re separated by 130,000 lightyears (or 1.22 billion billion km). This is all of the extra outstanding contemplating the Bullseye Galaxy is sort of 2.5-times bigger than the Milky Way with a diameter of 250,000 light-years.
On cosmic timescales, galaxies crash or barely miss each other comparatively usually. But even then it is extremely uncommon for one galaxy to actually dart via the core of one other. The blue dwarf galaxy’s straight path via the Bullseye Galaxy triggered fuel within the latter to ripple forwards and backwards in waves, creating new locations of star formation. The interplay didn’t alter the orbits of particular person stars but it surely triggered teams of stars to pile up and type the distinct rings over hundreds of thousands of years.
The Bullseye Galaxy will proceed to evolve and, in consequence, could have these star-filled rings just for a brief interval of time. This means the astronomers captured an intriguing picture of a multi-ring galaxy in a particular second.
For different astronomers, nonetheless, the intrigue may run even deeper: the Bullseye Galaxy also accommodates indicators that it may in the future evolve into a large low floor brightness (GLSB) galaxy, that are essential within the examine of dark matter.
Their findings had been revealed in February in The Astrophysical Journal Letters.
Cosmic oddballs
Low surface-brightness galaxies have a scarcity of components heavier than hydrogen and helium. They also have little or no star formation regardless of possessing massive disks crammed with hydrogen, the first gas for brand new stars. Scientists haven’t been capable of clarify this paradox. These galaxies are also believed to be crammed with dark matter, making them glorious targets of examine if scientists are to grasp this still-mysterious type of matter.
These galaxies also have a extra uniform distribution of mass close to their centres — which is at odds with the usual mannequin of cosmology, which predicts the centres of galaxies to be much more dense. This discrepancy is one other problem scientists are attempting to beat with extra information and higher theories.
Giant low floor brightness (GLSB) galaxies are the biggest of the low surface-brightness galaxies. All GLSB galaxies are really colossal. Their most well-known member, known as Malin 1, is roughly 6.5-times wider than the Milky Way and one of many largest spiral galaxies identified.
“GLSB galaxies are spiral galaxies that possess very diffuse or low surface density stellar disks, yet they are embedded within large neutral hydrogen gas disks,” stated Mousumi Das, a professor on the Indian Institute of Astrophysics, Bengaluru, who specialises in low-surface brightness galaxies amongst different areas.
She added that the mass of black holes on the facilities of those galaxies is also decrease than typical, which means they aren’t totally developed.
Given the assorted methods wherein LSBs deviate from the patterns that unite different galaxies, astronomers have struggled to grasp them. Their simulations, that are primarily based on the usual mannequin of cosmology, predict these galaxies’ hydrogen content material, the floor brightness of their disks, and their density profiles — just for them to be at odds with what astronomers see within the information collected by telescopes and observatories.
In science, such a disagreement means the scientific theories are not directly incomplete.
There are some concepts to resolve the disagreement. Das supplied one instance: “Previous studies have indicated that the dark-matter halos surrounding these galaxies spin more rapidly than expected,” a course of she likened to “how clay behaves on a spinning potter’s wheel. As the wheel turns, the clay spreads and thins out. In the same way, as these dark-matter halos rotate rapidly, the material within them expands outward, creating a large, disk-like shape with a low density,” and ultimately GLSB galaxies.
“And their disks are not dense enough to easily form stars.”
Studying GLSB galaxies in additional element may assist verify whether or not this concept, and others prefer it, may very well be true.
This in flip makes confirming whether or not newfound galaxies just like the Bullseye may very well be GLSB galaxies in future extra essential.
New perception
The worldwide group of researchers reported that the scale of the Bullseye Galaxy’s prolonged disk and hydrogen content material relative to its stellar mass are corresponding to that of different GLSB galaxies, and that it’s more likely to change into one in future. But of their paper they had been also cautious so as to add that extra evaluation remains to be required.
Das stated, “The transition from a ringed galaxy to a GLSB galaxy is still a theory that is being explored” and that “past simulations have demonstrated that some GLSB galaxies may have formed from head-on collisions between disk galaxies”, as within the Bullseye Galaxy’s case. But she also stated most GLSB galaxies are present in isolation — i.e. not surrounded by different galaxies close by — making it much less probably for them to have skilled such collisions.
In different phrases, confirming Bullseye’s candidacy as a pre-GLSB galaxy is sophisticated.
A tenth ring?
At this second, astronomers have a possibility to acquire the primary direct observational proof of a collisional ring galaxy turning right into a GLSB galaxy — or not.
Das expressed optimism as a result of, she stated, the brand new examine provides compelling proof of an evolutionary hyperlink between the Bullseye Galaxy and GLSB galaxies.
The authors of the brand new examine have also stated the Bullseye Galaxy may as soon as have had a tenth ring that has since pale. They added that over billions of years following the collision, the nine rings will also slowly drift out and fade away, abandoning a GLSB galaxy.
Das added that extra details about the formation of GLSB galaxies may reveal new insights into the distribution of dark matter within the universe. Eventually, “if the [current] theoretical models are correct, we should see GLSB-like galaxies in the results of cosmological simulations.”
Shreejaya Karantha is a contract science author and a content material author and analysis specialist at The Secrets of The Universe.
Published – April 22, 2025 05:30 am IST
