First discovered 60 years ago, quasars can shine as brightly as a trillion stars packed into a volume the size of our Solar System. In the decades since they were first observed, it has remained a mystery what could trigger such powerful activity. New work led by scientists at the Universities of Sheffield and Hertfordshire has now revealed that it is a consequence of galaxies crashing together.

The collisions were discovered when researchers, using deep imaging observations from the Isaac Newton Telescope in La Palma, observed the presence of distorted structures in the outer regions of the galaxies that are home to quasars.

Most galaxies have supermassive black holes at their centres. They also contain substantial amounts of gas — but most of the time this gas is orbiting at large distances from the galaxy centres, out of reach of the black holes. Collisions between galaxies drive the gas towards the black hole at the galaxy centre; just before the gas is consumed by the black hole, it releases extraordinary amounts of energy in the form of radiation, resulting in the characteristic quasar brilliance.

The ignition of a quasar can have dramatic consequences for entire galaxies — it can drive the rest of the gas out of the galaxy, which prevents it from forming new stars for billions of years into the future.

This is the first time that a sample of quasars of this size has been imaged with this level of sensitivity. By comparing observations of 48 quasars and their host galaxies with images of over 100 non-quasar galaxies, researchers concluded that galaxies hosting quasars are approximately three times as likely to be interacting or colliding with other galaxies.

The study has provided a significant step forward in our understanding of how these powerful objects are triggered and fuelled.

Professor Clive Tadhunter, from the University of Sheffield’s Department of Physics and Astronomy, said: “Quasars are one of the most extreme phenomena in the Universe, and what we see is likely to represent the future of our own Milky Way galaxy when it collides with the Andromeda galaxy in about five billion years.

“It’s exciting to observe these events and finally understand why they occur — but thankfully Earth won’t be anywhere near one of these apocalyptic episodes for quite some time.”

Quasars are important to astrophysicists because, due to their brightness, they stand out at large distances and therefore act as beacons to the earliest epochs in the history of the Universe. Dr Jonny Pierce, Post-Doctoral Research Fellow at the University of Hertfordshire, explains:

“It’s an area that scientists around the world are keen to learn more about — one of the main scientific motivations for NASA’s James Webb Space Telescope was to study the earliest galaxies in the Universe, and Webb is capable of detecting light from even the most distant quasars, emitted nearly 13 billion years ago. Quasars play a key role in our understanding of the history of the Universe, and possibly also the future of the Milky Way.”

Mild traumatic brain injury — concussion — results from a blow or jolt to the head. It can occur as a result of a fall, a sports injury or from a cycling accident or car crash, for example. But despite being labelled ‘mild’, it is commonly linked with persistent symptoms and incomplete recovery. Such symptoms include depression, cognitive impairment, headaches, and fatigue.

While some clinicians in recent studies predict that nine out of 10 individuals who experience concussion will have a full recovery after six months, evidence is emerging that only a half achieve a full recovery. This means that a significant proportion of patients may not receive adequate post-injury care.

Predicting which patients will have a fast recovery and who will take longer to recover is challenging, however. At present, patients with suspected concussion will typically receive a brain scan — either a CT scan or an MRI scan, both of which look for structural problems, such as inflammation or bruising — yet even if these scans show no obvious structural damage, a patient’s symptoms may still persist.

Dr Emmanuel Stamatakis from the Department of Clinical Neurosciences and Division of Anaesthesia at the University of Cambridge said: “Worldwide, we’re seeing an increase in the number of cases of mild traumatic brain injury, particularly from falls in our ageing population and rising numbers of road traffic collisions in low- and middle-income countries.

“At present, we have no clear way of working out which of these patients will have a speedy recovery and which will take longer, and the combination of over-optimistic and imprecise prognoses means that some patients risk not receiving adequate care for their symptoms.”

Dr Stamatakis and colleagues studied fMRI brain scans — that is, functional MRI scans, which look at how different areas of the brain coordinate with each other — taken from 108 patients with mild traumatic brain injury and compared them with scans from 76 healthy volunteers. Patients were also assessed for ongoing symptoms.

The patients and volunteers had been recruited to CENTER-TBI, a large European research project which aims to improve the care for patients with traumatic brain injury, co-chaired by Professor David Menon (head of the division of Anaesthesia) and funded by the European Union.

In results published today in Brain, the team found that just under half (45%) were still showing symptoms resulting from their brain injury, with the most common being fatigue, poor concentration and headaches.

The researchers found that these patients had abnormalities in a region of the brain known as the thalamus, which integrates all sensory information and relays this information around the brain. Counter-intuitively, concussion was associated with increased connectivity between the thalamus and the rest of the brain — in other words, the thalamus was trying to communicate more as a result of the injury — and the greater this connectivity, the poorer the prognosis for the patient.

Rebecca Woodrow, a PhD student in the Department of Clinical Neuroscience and Hughes Hall, Cambridge, said: “Despite there being no obvious structural damage to the brain in routine scans, we saw clear evidence that the thalamus — the brain’s relay system — was hyperconnected. We might interpret this as the thalamus trying to over-compensate for any anticipated damage, and this appears to be at the root of some of the long-lasting symptoms that patients experience.”

By studying additional data from positron emission tomography (PET) scans, which can measure regional chemical composition of body tissues, the researchers were able to make associations with key neurotransmitters depending on which long-term symptoms a patient displayed. For example, patients experiencing cognitive problems such as memory difficulties showed increased connectivity between the thalamus and areas of the brain rich in the neurotransmitter noradrenaline; patients experiencing emotional symptoms, such as depression or irritability, showed greater connectivity with areas of the brain rich in serotonin.

Dr Stamatakis, who is also Stephen Erskine Fellow at Queens’ College, Cambridge, added: “We know that there already drugs that target these brain chemicals so our findings offer hope that in future, not only might we be able to predict a patient’s prognosis, but we may also be able to offer a treatment targeting their particular symptoms.”

In new 3D computer simulations, astrophysicists modeled black holes of varying masses and then hurled stars (about the size of our sun) past them to see what might happen.

When a star approaches an intermediate-mass black hole, it initially gets caught in the black hole’s orbit, the researchers discovered. After that, the black hole begins its lengthy and violent meal. Every time the star makes a lap, the black hole takes a bite — further cannibalizing the star with each passage. Eventually, nothing is left but the star’s misshapen and incredibly dense core.

At that point, the black hole ejects the remains. The star’s remnant flies to safety across the galaxy.

Not only do these new simulations hint at the unknown behaviors of intermediate-mass black holes, they also provide astronomers with new clues to help finally pinpoint these hidden giants within our night sky.

“We obviously cannot observe black holes directly because they don’t emit light,” said Northwestern’s Fulya Kıroğlu, who led the study. “So, instead, we have to look at the interactions between black holes and their environments. We found that stars undergo multiple passages before being ejected. After each passage, they lose more mass, causing a flair of light as its ripped apart. Each flare is brighter than the last, creating a signature that might help astronomers find them.”

Kıroğlu will present this research during the virtual portion of the American Physical Society’s (APS) April meeting. “Tidal disruption events of stars by intermediate-mass black holes” will take place on April 25, as a part of the session “Medium: Cosmic Rays, AGN & Galaxies.” . The Astrophysical Journal has accepted the study for publication.

Kıroğlu is an astrophysics graduate student at Northwestern’s Weinberg College of Arts and Sciences and member of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). She is advised by paper co-author Frederic Rasio, the Joseph Cummings Professor of Physics and Astronomy at Weinberg and member of CIERA.

While astrophysicists have proven the existence of lower- and higher-mass block holes, intermediate-mass black holes have remained elusive. Created when supernovae collapse, stellar remnant black holes are about 3 to 10 times the mass of our sun. On the other end of the spectrum, supermassive black holes, which lurk in the centers of galaxies, are millions to billions times the mass of our sun.

Should they exist, intermediate-mass black holes would fit somewhere in the middle — 10 to 10,000 times more massive than stellar remnant black holes but not nearly as massive as supermassive black holes. Although these intermediate-mass black holes theoretically should exist, astrophysicists have yet to find indisputable observational evidence.

“Their presence is still debated,” Kıroğlu said. “Astrophysicists have uncovered evidence that they exist, but that evidence can often be explained by other mechanisms. For example, what appears to be an intermediate-mass black hole might actually be the accumulation of stellar-mass black holes.”

To explore the behavior of these evasive objects, Kıroğlu and her team developed new hydrodynamic simulations. First, they created a model of a star, consisting of many particles. Then, they sent the star toward the black hole and calculated the gravitational force acting on the particles during the star’s approach.

“We can calculate specifically which particle is bound to the star and which particle is disrupted (or no longer bound to the star),” Kıroğlu said.

Through these simulations, Kıroğlu and her team discovered that stars could orbit an intermediate-mass black hole as many as five times before finally being ejected. With each pass around the black hole, the star loses more and more of its mass as its ripped apart. Then, the black hole kicks the leftovers — moving at searing speeds — back out into the galaxy. The repeating pattern would create a stunning light show that should help astronomers recognize — and prove the existence of — intermediate-mass black holes.

“It’s amazing that the star isn’t fully ripped apart,” Kıroğlu said. “Some stars might get lucky and survive the event. The ejection speed is so high that these stars could be identified as hyper-velocity stars, which have been observed at the centers of galaxies.”

Next, Kıroğlu plans to simulate different types of stars, including giant stars and binary stars, to explore their interactions with black holes.

The robot fish was fitted with a twisted and coiled polymer (TCP) to drive it forward, a light-weight low cost device that relies on temperature change to generate movement, which also limits its speed.

A TCP works by contracting like muscles when heated, converting the energy into mechanical motion . The TCP used in this work is warmed by Joule heating — the pass of current through an electrical conductor produces thermal energy and heats up the conductor. By minimising the distance between the TCP on one side of the robot fish and the spring on the other, this activates the fin at the rear, enabling the robot fish to reach new speeds. The undulating flapping of its rear fin was measured at a frequency of 2Hz, two waves per second. The frequency of the electric current is the same as the frequency of tail flap.

The findings, published at the 6th IEEE-RAS International Conference on Soft Robotics (RoboSoft 2023), provide a new route to raising the actuation — the action of causing a machine or device to operate — frequency of TCPs through thermomechanical design and shows the possibility of using TCPs at high frequency in aqueous environments.

Lead author Tsam Lung You from Bristol’s Department of Engineering Mathematics said: “Twisted and coiled polymer (TCP) actuator is a promising novel actuator, exhibiting attractive properties of light weight, low-cost high energy density and simple fabrication process.

“They can be made from very easily assessable materials such as a fishing line and they contract and provide linear actuation when heated up. However, because of the time needed for heat dissipation during the relaxation phase, this makes them slow.”

By optimising the structural design of the TCP-spring antagonistic muscle pair and bringing their anchor points closer together, it allowed the posterior fin to swing at a larger angle for the same amount of TCP actuation.

Although this requires greater force, TCP is a strong actuator with high work energy density, and is still able to drive the fin.

Until now, TCPs have been mostly used for applications such as wearable devices and robotic hands. This work opens up more areas of application where TCP can be used, such as marine robots for underwater exploration and monitoring.

Tsam Lung You added: “Our robotic fish swam at the fastest actuation frequency found in a real TCP application and also the highest locomotion speed of a TCP application so far.

“This is really exciting as it opens up more opportunities of TCP application in different areas.”

The team now plan to expand the scale and develop a knifefish-inspired TCP-driven ribbon fin robot that can swim agilely in water.

Although mudskippers are distantly related to tetrapods, the group that includes humans and other four-limbed vertebrates, researchers believed studying the fish could unlock how blinking evolved as these animals began to move on land.

The research team, which included several undergraduates, published their findings in the paper, “The Origin of Blinking in Both Mudskippers and Tetrapods Is Linked to Life on Land,” in Proceedings of the National Academies of Science.

“By comparing the anatomy and behavior of mudskippers to the fossil record of early tetrapods, we argue that blinking emerged in both groups as an adaptation to life on land,” said Tom Stewart, an assistant professor at Penn State and an author of the paper. “These results help us understand our own biology and raise a whole set of new questions about the variety of blinking behaviors we see in living species.”

Breaking Down Blinking

Mudskippers blink by sucking their eye downward into their eye socket. The evolution of this behavior did not require the evolution of a lot of new parts such as new muscles or special glands, though. Instead, mudskippers use their existing set of eye muscles in a new way.

“This is a very exciting result because it demonstrates that the evolution of a new, complex behavior can be achieved using a relatively rudimentary set of structures,” said Brett Aiello, a former postdoctoral fellow in the Agile Systems Lab and now assistant professor at Seton Hill.

Next, the research team set out to determine why mudskippers blink. In a series of experiments, they found that mudskippers blink for three main functions: to wet, clean, and protect the eye. These functions are also why humans and other land-dwelling vertebrates blink.

“We find that a single behavior can be deployed to accomplish three complex, distinct functions,” said Aiello. “These results not only help humans understand our own history, but also help us reevaluate the adaptations necessary for major transitions in the evolutionary history of vertebrates, like moving from water to land.”

Blinking isn’t just a unique research question, but also an important mechanism to understand, according to Saad Bhamla, an assistant professor in Georgia Tech’s School of Chemical and Biomolecular Engineering and author on the paper.

“We all blink without thinking, and understanding why we blink is just such a beautiful puzzle right in front of our eyes,” Bhamla said. “Through our research on mudskippers and by conducting biophysical and morphological analyses, we expose how blinking serves a multitude of functions for adapting to life out of water.”

Engaging Undergraduates

To explore such open-ended questions, the researchers engaged the Vertically Integrated Projects (VIP) program, which allows undergraduates to conduct long-term, large-scale research projects as part of their coursework at Georgia Tech.

“The structure of the VIP course empowers students to really lean on their own creativity and drive the project in the directions that are most exciting to them,” said Aiello. “It helps our students gain the ability to solve unknown problems on the ground as they arise — a lot of people become scientists to push research somewhere where nobody else has tried to go before.”

The VIP structure is inherently multidisciplinary. While Aiello is a biologist, most students were engineers and brought their respective expertise. Manognya Sripathi was a biomedical engineering major with a minor in computer science and offered her unique experience to the mudskipper problem.

“I used my computer science skills to gather raw data and analyze and plot them using programs like MATLAB or Python,” Sripathi said. “I also used engineering skills to help build the experimental equipment, allowing us to apply engineering methods to study a biological problem in a unique way.”

Moving Beyond Mudskippers

Te research didn’t just expand knowledge of mudskippers — it also contributed to each student’s future aspirations. For example, Kendra Washington’s trajectory was influenced by the two semesters she spent in the lab.

“VIP drew me closer to the programming and device areas of my biomedical engineering major and solidified why I picked up a computer science minor,” she said. “I continued to pursue that fusion through later internships and research, and now work with hemodynamic monitoring. But in a sense, I still help characterize physiology through programming.”

VIP also expanded the students’ knowledge and scientific experience that have propelled them far beyond the lab. Hajime Minoguchi, a biomedical engineering graduate, now works as a systems integration research and development engineer thanks to his experience in the class.

“Working in an interdisciplinary team like this has allowed me to learn how to understand and communicate ideas between disciplines, which allowed me to be a more well-rounded engineer,” Minoguchi said. “My work requires a thorough understanding of biology, electrical circuitry, software, firmware, mechanical interactions, and physics. This VIP experience was instrumental for me in being successful at my current job.”

The research is far greater than the sum of its parts and brings a greater understanding of evolution, noted Simon Sponberg, an associate professor in the School of Physics and the School of Biological Sciences.

“Blinking is a reflection of a bigger question,” Sponberg said. “How did major evolutionary transitions occur that enabled organisms to inhabit basically every environment on this planet? What we learned is you don’t need the evolution of a lot of specialized musculature or glands; evolution can tinker with the structures that are already there, allowing them to be used in a new way and for a new behavior.”

An international research team — which included University of Maryland seismologists — used seismic data acquired by the NASA InSight lander to directly measure properties of Mars’s core, finding a completely liquid iron-alloy core with high percentages of sulfur and oxygen. Published in the Proceedings of the National Academy of Sciences on April 24, 2023, these findings reveal new insights into how Mars formed and geological differences between Earth and Mars that may ultimately play a role in sustaining planetary habitability.

“In 1906, scientists first discovered the Earth’s core by observing how seismic waves from earthquakes were affected by traveling through it,” said UMD Associate Professor of Geology Vedran Lekic, second author of the paper. “More than a hundred years later, we’re applying our knowledge of seismic waves to Mars. With InSight, we’re finally discovering what’s at the center of Mars and what makes Mars so similar yet distinct from Earth.”

To determine these differences, the team tracked the progression of two distant seismic events on Mars, one caused by a marsquake and the other by a large impact, and detected waves that traveled through the planet’s core. By comparing the time it took those waves to travel through Mars compared to waves that stayed in the mantle, and combining this information with other seismic and geophysical measurements, the team estimated the density and compressibility of the material the waves traveled through. The researchers’ results indicated that Mars most likely has a completely liquid core, unlike Earth’s combination of a liquid outer core and solid inner core.

Additionally, the team inferred details about the core’s chemical composition, such as the surprisingly large amount of light elements (elements with low atomic numbers) — namely sulfur and oxygen — present in Mars’ innermost layer. The team’s findings suggested that a fifth of the core’s weight is made up of those elements. This high percentage differs sharply from the comparatively lesser weight proportion of light elements in Earth’s core, indicating that Mars’ core is far less dense and more compressible than Earth’s core, a difference that points to different conditions of formation for the two planets.

“You can think of it this way; the properties of a planet’s core can serve as a summary about how the planet formed and how it evolved dynamically over time. The end result of the formation and evolution processes can be either the generation or absence of life-sustaining conditions,” explained UMD Associate Professor of Geology Nicholas Schmerr, another co-author of the paper. “The uniqueness of Earth’s core allows it to generate a magnetic field that protects us from solar winds, allowing us to keep water. Mars’ core does not generate this protective shield, and so the planet’s surface conditions are hostile to life.”

Although Mars does not currently have a magnetic field, scientists hypothesize that there was once a magnetic shielding similar to Earth’s core-generated field due to traces of magnetism lingering in Mars’ crust. Lekic and Schmerr noted that this might mean that Mars gradually evolved to its current conditions, changing from a planet with a potentially habitable environment into an incredibly hostile one. Conditions in the interior play a key role in this evolution, as might violent impacts, according to the researchers.

“It’s like a puzzle in some ways,” Lekic said. “For example, there are small traces of hydrogen in Mars’ core. That means that there had to be certain conditions that allowed the hydrogen to be there, and we have to understand those conditions in order to understand how Mars evolved into the planet it is today.”

The team’s findings have ultimately confirmed the accuracy of current modeling estimates that aim to unravel the layers hidden beneath a planet’s surface. For geophysicists like Lekic and Schmerr, research like this is also paving the way for future geophysics-oriented expeditions to other celestial bodies, including planets like Venus and Mercury.

“This was a huge effort, involving state-of-the-art seismological techniques which have been honed on Earth, in conjunction with new results from mineral physicists and the insights from team members who simulate how planetary interiors change over time,” noted Jessica Irving, a senior lecturer at Bristol University and first author of the study. “But the work paid off, and we now know much more about what’s happening inside the Martian core.”

“Even though the InSight mission ended in December 2022 after four years of seismic monitoring, we’re still analyzing the data that was collected,” Lekic said. “InSight will continue to influence how we understand the formation and evolution of Mars and other planets for years to come.”