Latest news with #BullseyeGalaxy
The Hindu
22-04-2025
- Science
- The Hindu
Bullseye! Galaxy with nine rings may also reveal dark matter secrets
A team of international researchers recently discovered a galaxy with nine rings. They called it a 'serendipitous discovery' because previous ringed galaxies have only displayed two or three rings at best. Using the Hubble space telescope, the team confirmed the presence of eight rings, while data from the W.M. Keck Observatory in Hawaii confirmed the existence of the ninth ring. This unusual galaxy has been named LEDA 1313424 but its common name is more memorable: the Bullseye Galaxy. The story of how its rings could have formed may render it more memorable. A thin trail of evidence When the researchers analysed the data from the space telescope and the observatory, they found signs that a blue dwarf galaxy, located at the immediate centre-left in an image, had passed through the centre of the Bullseye Galaxy about 50 million years ago. They have said this interaction gave the Bullseye Galaxy its unique shape. As evidence of this interaction, the team reported a thin trail of gas connecting the two galaxies even though they are separated by 130,000 lightyears (or 1.22 billion billion km). This is all the more remarkable considering the Bullseye Galaxy is nearly 2.5-times larger than the Milky Way with a diameter of 250,000 light-years. On cosmic timescales, galaxies crash or barely miss one another relatively often. But even then it is very rare for one galaxy to literally dart through the core of another. The blue dwarf galaxy's straight path through the Bullseye Galaxy caused gas in the latter to ripple back and forth in waves, creating new places of star formation. The interaction didn't alter the orbits of individual stars but it caused groups of stars to pile up and form the distinct rings over millions of years. The Bullseye Galaxy will continue to evolve and, as a result, will have these star-filled rings only for a short interval of time. This means the astronomers captured an intriguing image of a multi-ring galaxy in a special moment. For other astronomers, however, the intrigue may run even deeper: the Bullseye Galaxy also contains signs that it could one day evolve into a giant low surface brightness (GLSB) galaxy, which are important in the study of dark matter. Their findings were published in February in The Astrophysical Journal Letters. Cosmic oddballs Low surface-brightness galaxies have a shortage of elements heavier than hydrogen and helium. They also have very little star formation despite possessing large disks filled with hydrogen, the primary fuel for new stars. Scientists haven't been able to explain this paradox. These galaxies are also believed to be filled with dark matter, making them excellent targets of study if scientists are to understand this still-mysterious form of matter. These galaxies also have a more uniform distribution of mass near their centres — which is at odds with the standard model of cosmology, which predicts the centres of galaxies to be a lot more dense. This discrepancy is another challenge scientists are trying to overcome with more data and better theories. Giant low surface brightness (GLSB) galaxies are the largest of the low surface-brightness galaxies. All GLSB galaxies are truly colossal. Their most famous member, called Malin 1, is roughly 6.5-times wider than the Milky Way and one of the largest spiral galaxies known. '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,' said Mousumi Das, a professor at the Indian Institute of Astrophysics, Bengaluru, who specialises in low-surface brightness galaxies among other areas. She added that the mass of black holes at the centers of these galaxies is also lower than usual, meaning they aren't fully evolved. Given the various ways in which LSBs deviate from the patterns that unite other galaxies, astronomers have struggled to understand them. Their simulations, which are based on the standard model of cosmology, predict these galaxies' hydrogen content, the surface brightness of their disks, and their density profiles — only for them to be at odds with what astronomers see in the data collected by telescopes and observatories. In science, such a disagreement means the scientific theories are in some way incomplete. There are some ideas to resolve the disagreement. Das offered one example: 'Previous studies have indicated that the dark-matter halos surrounding these galaxies spin more rapidly than expected,' a process 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 eventually GLSB galaxies. 'And their disks are not dense enough to easily form stars.' Studying GLSB galaxies in more detail could help check whether this idea, and others like it, could be true. This in turn makes confirming whether newfound galaxies like the Bullseye could be GLSB galaxies in future more important. New insight The international team of researchers reported that the size of the Bullseye Galaxy's extended disk and hydrogen content relative to its stellar mass are comparable to that of other GLSB galaxies, and that it's likely to become one in future. But in their paper they were also careful to add that more analysis is still required. Das said, '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 in the Bullseye Galaxy's case. But she also said most GLSB galaxies are found in isolation — i.e. not surrounded by other galaxies nearby — making it less likely for them to have experienced such collisions. In other words, confirming Bullseye's candidacy as a pre-GLSB galaxy is complicated. A 10th ring? At this moment, astronomers have an opportunity to obtain the first direct observational evidence of a collisional ring galaxy turning into a GLSB galaxy — or not. Das expressed optimism because, she said, the new study offers compelling evidence of an evolutionary link between the Bullseye Galaxy and GLSB galaxies. The authors of the new study have also said the Bullseye Galaxy may once have had a 10th ring that has since faded. They added that over billions of years following the collision, the nine rings will also slowly drift out and fade away, leaving behind a GLSB galaxy. Das added that more information about the formation of GLSB galaxies could reveal new insights into the distribution of dark matter in 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 freelance science writer and a content writer and research specialist at The Secrets of The Universe.
Yahoo
06-02-2025
- Science
- Yahoo
Hubble Reveals Cosmic Bullet That Gave The Bullseye Galaxy Its Record-Breaking Rings
Just like fingerprints and snowflakes, no two galaxies in the entire Universe are exactly alike. But a new discovery 567 million light-years away really is jaw-droppingly unique. There, astronomers have found a galaxy girdled by, not one, but nine concentric rings – the aftermath of a violent encounter with a blue dwarf galaxy that shot right through its heart, sending shockwaves rippling out into space. Officially named LEDA 1313424, this galaxy has been given the appropriate title of the Bullseye Galaxy, and its serendipitous discovery is a new window into galaxy-on-galaxy crime. "We're catching the Bullseye at a very special moment in time," says astronomer Pieter van Dokkum of Yale University. "There's a very narrow window after the impact when a galaxy like this would have so many rings." So-called ring galaxies are extremely rare in the Universe, and they are thought to be the result of a very specific set of circumstances. Although space is mostly empty, galaxies are drawn together along filaments of the cosmic web, resulting in more collisions between them than you might expect. Interactions between galaxies can take many forms, and produce varied results. Ring galaxies – such as the mysterious and famous Hoag's Object – are thought to be the result of a collision in which one galaxy blasts straight through the center of another. The Bullseye Galaxy has confirmed that this process does indeed take place. Not far from the larger galaxy is a smaller one, seen in visible light images using the Hubble Space Telescope. Observations taken using the Keck Cosmic Web Imager (KCWI), which is optimized for visible blue wavelengths, revealed that this smaller galaxy is not only close to Bullseye, at a distance of just 130,000 kilometers (about 80,000 miles), but linked. "KCWI provided the critical view of this companion galaxy that we see in projection near the bullseye," says astronomer Imad Pasha of Yale University. "We found a clear signature of gas extending between the two systems, which allowed us to confirm that this galaxy is in fact the one that flew through the center and produced these rings." "The data from KCWI that identified the 'dart' or impactor is unique. There hasn't been any other case where you can so clearly see the gas streaming from one galaxy to the other, " van Dokkum adds. "That there is all this gas right between the velocity of one galaxy and the other is the key insight, showing that material is being pulled out of one galaxy, left behind by the other, or both. It physically fills up the entire space. The KCWI data enables us to see the tendril of gas that is still connecting these two galaxies." The rings are regions of higher density, where the galactic material has been pushed together by the rippling shocks. The clumping of the dust and gas triggers star formation, resulting in higher star density, which is why the rings glitter so brightly. The most distant ring is relatively faint and tenuous, and was only spotted in the KCWI images, at quite a distance from the main body of the galaxy. The entire galaxy is 250,000 light-years across. That gap between the rings is a marvel, showing that the rings propagate outwards in almost exactly the same way as predicted by theory, with the first two rings spreading quickly, with the subsequent rings forming later. It's like dropping a pebble in a pond. "If we were to look down at the galaxy directly, the rings would look circular, with rings bunched up at the center and gradually becoming more spaced out the farther out they are," Pasha says. The data provided by this marvelous galaxy will help astronomers adjust their models and theories, to better understand how such collisions play out. The researchers also hope future observations with upcoming telescopes will ferret out even more ring galaxies, lurking out there in the wide expanses of the cosmos. The research has been published in The Astrophysical Journal Letters. 10 Minutes of Violence Gave The Moon Its Very Own 'Grand Canyons' Astrophysicist Reveals The Key Facts About The Asteroid That May Hit Earth AI Can Predict Incredible Solar Storms Before They Strike
