Bullseye! Galaxy with 9 rings may additionally reveal darkish matter secrets and techniques

A workforce of worldwide researchers just lately found a galaxy with 9 rings. They referred to as it a “serendipitous discovery” as a result of earlier ringed galaxies have solely displayed two or three rings at greatest.

Utilizing the Hubble area telescope, the workforce confirmed the presence of eight rings, whereas knowledge 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 identify is extra memorable: the Bullseye Galaxy. The story of how its rings might have fashioned might render it extra memorable.

A skinny path of proof

When the researchers analysed the info from the area telescope and the observatory, they discovered indicators {that a} blue dwarf galaxy, positioned on the quick centre-left in a picture, had handed via the centre of the Bullseye Galaxy about 50 million years in the past. They’ve stated this interplay gave the Bullseye Galaxy its distinctive form.

As proof of this interplay, the workforce reported a skinny path of fuel connecting the 2 galaxies though they’re separated by 130,000 lightyears (or 1.22 billion billion km). That is all of the extra outstanding contemplating the Bullseye Galaxy is sort of 2.5-times bigger than the Milky Means with a diameter of 250,000 light-years. 

On cosmic timescales, galaxies crash or barely miss each other comparatively usually. However even then it is vitally uncommon for one galaxy to actually dart via the core of one other. The blue dwarf galaxy’s straight path via the Bullseye Galaxy brought about 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 brought about teams of stars to pile up and type the distinct rings over tens of millions of years.

The Bullseye Galaxy will proceed to evolve and, because of this, could have these star-filled rings just for a brief interval of time. This implies the astronomers captured an intriguing picture of a multi-ring galaxy in a particular second.

For different astronomers, nevertheless, the intrigue might run even deeper: the Bullseye Galaxy additionally comprises indicators that it might someday evolve into a large low floor brightness (GLSB) galaxy, that are vital within the examine of darkish matter.

Their findings have 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. In addition they have little or no star formation regardless of possessing giant disks stuffed with hydrogen, the first gas for brand spanking new stars. Scientists haven’t been in a position to clarify this paradox. These galaxies are additionally believed to be stuffed with darkish matter, making them glorious targets of examine if scientists are to grasp this still-mysterious type of matter.

These galaxies even 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 try to beat with extra knowledge and higher theories.

Large low floor brightness (GLSB) galaxies are the most important of the low surface-brightness galaxies. All GLSB galaxies are really colossal. Their most well-known member, referred to as Malin 1, is roughly 6.5-times wider than the Milky Means and one of many largest spiral galaxies recognized.

“GLSB galaxies are spiral galaxies that possess very diffuse or low floor density stellar disks, but they’re embedded inside giant impartial hydrogen fuel 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 can also be decrease than typical, which means they aren’t absolutely advanced.

Given the assorted methods during which LSBs deviate from the patterns that unite different galaxies, astronomers have struggled to grasp them. Their simulations, that are based mostly 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 knowledge collected by telescopes and observatories.

In science, such a disagreement means the scientific theories are in a roundabout way incomplete.

There are some concepts to resolve the disagreement. Das provided one instance: “Earlier research have indicated that the dark-matter halos surrounding these galaxies spin extra quickly than anticipated,” a course of she likened to “how clay behaves on a spinning potter’s wheel. Because the wheel turns, the clay spreads and thins out. In the identical approach, as these dark-matter halos rotate quickly, the fabric inside them expands outward, creating a big, disk-like form with a low density,” and ultimately GLSB galaxies.

“And their disks usually are not dense sufficient to simply type stars.”

Finding out GLSB galaxies in additional element might assist examine 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 vital.

New perception

The worldwide workforce of researchers reported that the scale of the Bullseye Galaxy’s prolonged disk and hydrogen content material relative to its stellar mass are akin to that of different GLSB galaxies, and that it’s prone to change into one in future. However of their paper they have been additionally cautious so as to add that extra evaluation continues to be required.

Das stated, “The transition from a ringed galaxy to a GLSB galaxy continues to be a idea that’s being explored” and that “previous simulations have demonstrated that some GLSB galaxies might have fashioned from head-on collisions between disk galaxies”, as within the Bullseye Galaxy’s case. However she additionally stated most GLSB galaxies are present in isolation — i.e. not surrounded by different galaxies close by — making it much less doubtless 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 gives compelling proof of an evolutionary hyperlink between the Bullseye Galaxy and GLSB galaxies.

The authors of the brand new examine have additionally stated the Bullseye Galaxy might as soon as have had a tenth ring that has since light. They added that over billions of years following the collision, the 9 rings may even slowly drift out and fade away, abandoning a GLSB galaxy.

Das added that extra details about the formation of GLSB galaxies might reveal new insights into the distribution of darkish matter within the universe. Finally, “if the [current] theoretical fashions are right, we should always see GLSB-like galaxies within the outcomes of cosmological simulations.”

Shreejaya Karantha is a contract science author and a content material author and analysis specialist at The Secrets and techniques of The Universe.