Category: 7. Science

New research shows that human activity is even more responsible for melting Arctic glaciers than previously thought.

What’s happening?

Yoon Jin-ho, an environmental engineering professor at South Korea’s Gwangju Institute of Science and Technology, has found that aerosol particles accelerate ice melt in the Arctic Ocean.

Maeil Business Newspaper reported on Yoon’s research, which studied the effects of these fine-dust particles on ice in the Chukchi Sea, which has seen the most rapid ice decrease in the Arctic.

Previously, aerosols — tiny particles suspended in the atmosphere — were thought to only have cooling effects, as they reflect sunlight. But Yoon found that Arctic ice melted more quickly when aerosols were combined with greenhouse gases.

Aerosols have this effect, Yoon said, because they increase high pressure, which brings stronger winds and warmer water to the Arctic.

“It shows that human activities can have a significant impact on the Arctic environment even in non-direct ways,” Yoon said. “The effects of aerosols should be reflected in future climate modeling and international environmental policy establishment.”

Why is this important?

As the study noted, aerosols aren’t the only contributing factor to Arctic ice melt.

Air pollution from greenhouse gases traps heat within our atmosphere, which is making our planet warmer. In fact, the 10 hottest years in recorded history have all occurred within the past decade, and experts don’t expect that trend to reverse anytime soon.

That warming has a devastating, cyclical effect on Arctic ice, which helps keep temperatures cool by reflecting sunlight. As temperatures increase, the ice melts, which plays a role in sea levels rising globally. So when warmer temperatures cause more ice to melt, that melting ice causes temperatures to get even warmer.

All of that plays a role in daily life far away from the Arctic. Studies have shown that, as more Arctic ice melts, weather patterns get disrupted thousands of miles away, raising the risk of extreme weather like heat waves and droughts.

What’s being done about this?

Yoon hopes his research will lead to the inclusion of aerosols’ effect on melting ice within scientific modeling, which will lead to more accurate projections about what the future of weather will look like.

Even though the Arctic may be thousands of miles away, there are still actions you can take at home to help. Seemingly small actions, such as walking more often or using less plastic each day, decrease your reliance on fossil fuels and the amount of pollution we create. And the more people that take these actions, the more of a difference it will make in our planet’s future.

Join our free newsletter for good news and useful tips, and don’t miss this cool list of easy ways to help yourself while helping the planet.

A labelled diagram of the human pelvis.
| Photo Credit: Public domain

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An international team kept solid gold intact while superheating it to 19,000 Kelvin, about 33,740 °F (18,726 °C). They measured the temperature directly, in real time, and documented the feat in a new study. The result outstrips a long assumed ceiling on how hot a solid can get before it gives way.

The team reached this state with ultra fast laser heating and then checked the atoms with precise X-ray probes.

The work also lays out a clean way to take the temperature of extremely hot, dense matter, which is something that has frustrated experimenters for decades.

What superheating gold means

Lead author Thomas G. White of the University of Nevada, Reno (UNR), led the international collaboration with colleagues at SLAC National Accelerator Laboratory and partner institutions.

The study focuses on superheating, which is when a solid sits above its melting point yet does not melt because the rapid conditions do not give its structure time to reorganize.

Here, the group pushed a thin gold sample far beyond its normal melting threshold in a flash.

The superheated gold remained crystalline for a brief window, long enough to record how fast the atoms were moving and therefore how hot the lattice was.

The work touches a broader frontier known as warm dense matter (WDM), which is a high energy state relevant to planetary interiors and fusion targets.

Accurate temperatures in this regime have been hard to pin down because these hot states are tiny and very short lived.

Why superheating gold matters

In 1988, Hans J. Fecht and William L. Johnson proposed an upper stability boundary called the entropy catastrophe, arguing that a solid cannot be heated much past about three times its melting temperature without melting.

The idea was that as a crystal heats, its entropy rises until it matches the liquid, which should trigger melting.

That back of the envelope limit, about three times the melting point, became the accepted stopping point in textbooks and talks.

It also aligned with the fact that most experiments ran into disordering events at lower temperatures anyway.

The new gold measurements show that ultra fast heating sidesteps those assumptions.

By outrunning processes that normally give a crystal time to expand and unravel, the team produced a much hotter solid phase without violating basic physics.

How the team pushed past the limit

The experiment used a brief pulse, only 45 femtoseconds long, to pump energy into a thin gold foil.

Immediately after this, an intense X-ray pulse captured the atomic motion through tiny shifts in the scattered X-ray frequency. This gave a direct readout of the atoms’ speeds.

Those shifts revealed the gold’s lattice temperature without relying on indirect models.

Because the heating was so swift, the lattice could not expand significantly during the measurement window, and crystalline order persisted for a few trillionths of a second.

The diagnostic hinges on inelastic X-ray scattering (IXS) which, in this fast backscattering geometry, records a clean spectral broadening linked to atomic velocities.

In short bursts, the technique treats the ion motion much like a classical gas and translates the line width into temperature.

Obeying the laws of thermodynamics

Direct temperature tracking matters because warm dense matter only exists for fleeting instants in the lab.

A reliable, model independent measurement gives planetary physicists and fusion researchers a sharper tool to test their calculations.

“It is important to clarify that we did not violate the Second Law of Thermodynamics. [But] the entropy catastrophe was still viewed as the ultimate boundary,” said White.

Outside voices have noted that ultrafast, ultrasmall conditions may not map cleanly onto everyday solids under normal pressure.

Even so, this controlled window lets researchers test long-standing assumptions about melting and stability with far less guesswork.

Heating gold for future technology

Better temperature measurements open doors for modeling planets, where WDM controls how heat moves through cores and mantles. Getting the temperature right helps set the melting curves that guide those models.

Fusion research also stands to gain. In inertial confinement experiments, laser driven targets quickly cross from solid to ultra hot states, and design choices depend on when and how those transitions occur.

There is a materials angle as well. If rapid heating can lift other solids far beyond past expectations without immediate melting, that would invite a rethink of strength, heat capacity, and failure in extreme environments.

The upshot is not that thermodynamics has been tossed out. It is that speed, and the lack of time for expansion, can keep order in place long enough to measure and learn from it.

Future work will likely try different elements, thicker targets, and varied time delays to map exactly when order fails. Each variation will test where the practical limits really lie and how general the no-longer-so- strict ceiling might be.

The full study is published in the journal Nature.

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For astrobiologists, the search for life beyond our Solar System could be likened to where one would look in a vast desert where there’s water. The most intriguing targets are planets called sub-Neptunes, which get their name because they’re larger than Earth but smaller than Neptune. What makes them fascinating is that their size and mass suggest they’re packed with water but not the kind of water we know.

These steam worlds orbit much closer to their host stars than Earth does to our Sun, making them far too hot for liquid oceans on their surfaces. Instead, they’re shrouded in thick steam atmospheres that hover over layers of water in an exotic “supercritical” state. This strange phase of water, which scientists have recreated in Earth laboratories, behaves in ways far more complex than simple liquid or ice.

Test unit of the sunshield stacked and expanded at the Northrop Grumman facility in California (Credit : Chris Gunn)

The James Webb Space Telescope has already detected steam on several sub-Neptunes, confirming what astronomers had theorised for decades. Now, with dozens more observations expected, researchers need better tools to interpret what they’re seeing.

The challenge lies in the extreme nature of these worlds. Previous models were designed for studying icy moons like Europa and Enceladus in our Solar System; small, cold bodies with icy crusts over liquid oceans. Sub-Neptunes are entirely different beasts, being 10 to 100 times more massive and subjected to crushing pressures and scorching temperatures that create water phases impossible to find on icy moons.

This is Europa in true colour, cropped from Juno’s flyby of Europa (Credit : NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill)

Under the most extreme conditions deep within these planets, water might even transform into “superionic ice,” a bizarre state where water molecules reorganise so that hydrogen ions move freely through an oxygen lattice. This phase has been produced in the lab and is thought to exist in the deep interiors of Uranus, Neptune, and potentially sub-Neptunes as well.

Led by postdoctoral researcher Artem Aguichine, the UC Santa Cruz team has created models that account for these exotic water phases and how they evolve over millions and billions of years.

“When we understand how the most commonly observed planets in the universe form, we can shift our focus to less common exoplanets that could actually be habitable,” – Artem Aguichine from UC Santa Cruz.

The research also serves as preparation for future missions. The European Space Agency’s upcoming PLATO telescope will search for Earth like planets in habitable zones, and these new models will help scientists interpret what they find. As Aguichine put it, the models are making predictions for telescopes while helping shape humanity’s next steps in searching for life beyond Earth.

Understanding these steam worlds matters because they’re everywhere, among the most common planets we’ve discovered. By deciphering how water behaves under such extreme conditions, we’re not just learning about distant worlds, but gaining insights into the fundamental processes that shape planetary systems throughout the universe.

Source : New model aims to demystify ‘steam worlds’ beyond our solar system

A breakthrough in stem cell biology has been 3D-printed in Minnesota—and the lab results show promise for spinal cord injury recovery, and even reversal.

A research team at the University of Minnesota Twin Cities demonstrated a groundbreaking process that combines 3D printing, stem cell biology, and lab-grown tissues to provide spinal cord injury recovery.

Currently there is no way to completely reverse the damage and paralysis. A major challenge is the death of nerve cells and the inability for nerve fibers to regrow across the injury site. This new research tackles this problem by building a bridge.

The team created a unique 3D-printed framework for lab-grown organs, called an organoid scaffold, with microscopic channels. These channels are then populated with ‘spinal neural progenitor cells’ derived from adult stem cells in humans, which have the capacity to divide and differentiate into specific types of mature cells.

“We use the 3D printed channels of the scaffold to direct the growth of the stem cells, which ensures the new nerve fibers grow in the desired way,” said Guebum Han PhD, a former University of Minnesota mechanical engineering researcher and first author of the paper published in Advanced Healthcare Materials, a peer-reviewed scientific journal.

“This method creates a relay system that when placed in the spinal cord bypasses the damaged area.”

In the study—funded by the NIH, the State of Minnesota Spinal Cord Injury and Traumatic Brain Injury Research Grant Program, and the Spinal Cord Society—the researchers transplanted these scaffolds into rats with spinal cords that were completely severed.

The cells successfully differentiated into neurons and extended their nerve fibers in both directions—rostral (toward the head) and caudal (toward the tail)—to form new connections with the host’s existing nerve circuits.

The new nerve cells integrated seamlessly into the host spinal cord tissue over time, leading to significant functional recovery in the rats.

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“Regenerative medicine has brought about a new era in spinal cord injury research,” said Ann Parr, professor of neurosurgery at the University of Minnesota. “Our laboratory is excited to explore the future potential of our ‘mini spinal cords’ for clinical translation.”

While the research is in its beginning stages, it offers a new avenue of hope for those with spinal cord injuries—and the team hopes to scale up production and continue developing this combination of technologies.

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What processes are responsible for our Sun’s solar wind, heat, and energy? This is what a recent study published in Physical Review X hopes to address as a team of researchers presented evidence for a newly discovered type of barrier that the Sun exhibits that could help explain the transfer of energy to heat within the Sun’s outer atmosphere. This study has the potential to help scientists better understand the underlying mechanisms for what drives our Sun and what this could mean for learning about other suns throughout the cosmos.

For the study, the researchers analyzed data obtained from NASA’s Parker Solar Probe, which has been studying the Sun for several years and is also the closest spacecraft to orbit the Sun in history. The goal of the study was to gain insight into how the Sun converts energy into heat, also called turbulent dissipation. The team conducted this by obtaining measurements and data about the Sun’s magnetic field, solar wind, plasma behavior, and the corona, the last of which exists in the Sun’s outer atmosphere.

In the end, the researchers presented evidence for the existence of what they refer to as the “helicity barrier”, which is a long-hypothesized boundary where small-scale energies influence the heating of plasma, which alters the solar wind.

“This paper is important as it provides clear evidence for the presence of the helicity barrier, which answers some long-standing questions about coronal heating and solar wind acceleration, such as the temperature signatures seen in the solar atmosphere, and the variability of different solar wind streams,” said Dr. Christopher Chen, who is a Reader in the Astronomy Unit of the Department of Physics and Astronomy at Queen Mary University of London and a co-author on the study. “This allows us to better understand the fundamental physics of turbulent dissipation, the connection between small-scale physics and the global properties of the heliosphere and make better predictions for space weather.”

Going forward, these findings could help scientists better understand stars in other solar systems, specifically how they convert energy to heat and what this could mean for the formation and evolution of exoplanets, including whether they could host life as we know it. The solar wind influences the Earth’s magnetic field, resulting in the auroras at the north and south polar regions, but if the solar wind is strong enough it could damage satellites and ground stations, which occurred on September 1-2, 1859, in an incident known as the Carrington Event. While the Earth’s magnetic field shields use from the Sun’s harmful radiation and solar wind, exoplanets orbiting other stars with stronger helicity barriers might be influenced differently.

Launched in August 2018, NASA’s Parker Solar Probe has been instrumental in teaching astronomers, specifically solar physics, more about our Sun than ever before. This has been accomplished due to Parker’s ability to travel dangerously close to the Sun using its white reflective shield to protect the scientific instruments designed to gather data about our Sun.

This incredible journey includes setting and breaking several of its records regarding its distance to Sun, with the closest being 6.1 million kilometers (3.8 million miles) from the Sun’s surface, which was accomplished on December 24, 2024. This passage marked the final gravity assist of the spacecraft with mission planners choosing to end the mission as the spacecraft will eventually burn all its fuel. Once this happens, it is slated to orbit the Sun for the next several million years.

What new discoveries about the Sun’s helicity barrier will researchers make in the coming years and decades? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!

Scientists from the University of Minnesota have discovered something extraordinary in Jupiter’s polar regions that has never been seen before, a completely new type of plasma wave that creates aurora unlike anything we observe on Earth.

While Earth’s northern and southern lights (also known as the aurora borealis and aurora australis) create familiar green and blue curtains dancing across our sky, Jupiter’s aurora is an entirely different beast. In comparison, Jupiter is vastly more magnetic, due to its large size, fast rotation, and complex interactions with its moons, make it a natural laboratory for extreme physics.

The Aurora Borealis, or Northern Lights, shines above Bear Lake (Credit : United States Air Force)

The discovery came from NASA’s Juno spacecraft, which made history as the first probe to orbit Jovian poles. What the team found challenges everything we thought we knew about aurora, which have primarily been understood through Earth based observations.

The key to this breakthrough is the nature of plasma. Plasma is a state of gas where matter is so hot that atoms break apart into electrons and ions. This then flows like an invisible ocean around Jupiter. These particles are accelerated down toward the planet, where they ignite gases in the upper atmosphere, creating the aurora phenomenon.

An illustration shows NASA’s Juno spacecraft near Io with its parent planet Jupiter in the background (Credit : NASA)

Professor Robert Lysak, a world expert on plasma waves, worked with observational astronomers Ali Sulaiman and Sadie Elliott to decode what Juno was seeing. They discovered that Jupiter’s unique conditions, an incredibly strong magnetic field combined with extremely low plasma density in its polar regions, created the never seen before phenomenon.

Alfvén waves, named after physicist Hannes Alfvén who first theorised in 1942 that plasma could behave like both a fluid and respond to magnetic fields are central to the phenomenon. The data showed that, due to the extremely low density of the plasma in Jupiter’s polar region, the frequency of the plasma waves was very low especially compared to the frequency of similar waves on Earth.

The differences between Earth and Jupiter’s auroral systems are striking. On Earth, the aurora forms a typical donut pattern of auroral activity around the polar cap, while the polar cap itself remains dark. Jupiter operates differently, thanks to its complex magnetic field system which allows charged particles to flood directly into the polar cap regions, creating aurora where Earth would have darkness.

Auroras shine bright blue over Jupiter (Credit : NASA/ESA)

Unlike Earth’s visible green and blue auroras created by oxygen and nitrogen, Jupiter’s upper atmosphere is very different from Earth’s and its aurora tends to be invisible to the naked eye and can only be observed with UV and Infrared instruments.

This discovery reveals an entirely new regime of plasma physics that couldn’t be observed from Earth based studies alone. The research expands our understanding of how plasma behaves under extreme conditions, knowledge that could have applications in fusion energy research and space weather prediction.

While Juno continues to orbit Jupiter, the team hopes future missions like JUICE and Europa Clipper, arriving at Jupiter in the late 2020s, will provide additional opportunities to study this phenomenon. Each new observation helps scientists piece together the complex puzzle of planetary magnetospheres and their role in shaping the space environment around giant planets.

Source : Alien Aurora: Lysak, Sulaiman and Elliott find new plasma regime in Jupiter’s aurora

Ancient droplets found in meteorites reveal the history of planet formation.

About 4.5 billion years ago, Jupiter expanded quickly into the giant planet we see today. Its immense gravity disturbed the paths of countless rocky and icy objects, known as planetesimals, which resembled present-day asteroids and comets.

These disturbances led to violent collisions so energetic that the rock and dust inside the planetesimals melted, producing droplets of molten rock called chondrules. Many of these ancient droplets are still preserved within meteorites that fall to Earth.

In a new breakthrough, scientists from Nagoya University in Japan and the Italian National Institute for Astrophysics (INAF) have uncovered how these chondrules were created and used them to precisely date Jupiter’s formation.

Their research, published in Scientific Reports, reveals that the traits of chondrules, including their size and cooling rates in space, were shaped by the amount of water present in the colliding planetesimals. This discovery not only matches what scientists observe in meteorite samples but also confirms that the birth of planets directly drove the creation of chondrules.

Time capsules from 4.6 billion years ago

Chondrules, small spheres approximately 0.1-2 millimeters wide, were incorporated into asteroids as the solar system formed. Billions of years later, pieces of these asteroids would break off and fall to Earth as meteorites. How chondrules came to have their round shape has puzzled scientists for decades.

“When planetesimals collided with each other, water instantly vaporized into expanding steam. This acted like tiny explosions and broke apart the molten silicate rock into the tiny droplets we see in meteorites today,” co-lead author Professor Sin-iti Sirono from Nagoya University’s Graduate School of Earth and Environmental Sciences explained.

“Previous formation theories couldn’t explain chondrule characteristics without requiring very specific conditions, while this model requires conditions that naturally occurred in the early solar system when Jupiter was born.”

The researchers developed computer simulations of Jupiter’s growth and tracked how its gravity caused high-speed collisions between rocky and water-rich planetesimals in the early solar system.

“We compared the characteristics and abundance of simulated chondrules to meteorite data and found that the model spontaneously generated realistic chondrules. The model also shows that chondrule production coincides with Jupiter’s intense accumulation of nebular gas to reach its massive size. As meteorite data tell us that peak chondrule formation took place 1.8 million years after the solar system began, this is also the time at which Jupiter was born,” Dr. Diego Turrini, co-lead author and senior researcher at the Italian National Institute for Astrophysics (INAF), said.

A new way to date when planets form

This study provides a clearer picture of how our solar system formed. However, the production of chondrules started by Jupiter’s formation is too brief to explain why we find chondrules of many different ages in meteorites. The most likely explanation is that other giant planets like Saturn also triggered chondrule formation when they were born.

By studying chondrules of different ages, scientists can trace the birth order of the planets and understand how our solar system developed over time. The research also suggests that these violent planet formation processes may occur around other stars and offers insights into how other planetary systems developed.

Reference: “Chondrule formation by collisions of planetesimals containing volatiles triggered by Jupiter’s formation” by Sin-iti Sirono, and Diego Turrini, 25 August 2025, Scientific Reports.
DOI: 10.1038/s41598-025-12643-x

This work was supported by JSPS KAKENHI Grant Number 25K07383, by the Italian Space Agency through ASI-INAF contract 2016-23-H.0 and 2021-5-HH.0 and by the European Research Council via the Horizon 2020 Framework Programme ERC Synergy “ECOGAL” Project GA-855130.

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What can binary star systems teach astronomers about the formation and evolution of planets orbiting them? This is what a recent study published in Nature hopes to address as a team of scientists investigated past studies that claimed a specific binary star system could host a planet demonstrating a retrograde orbit, meaning it orbits in the opposite direction of the star’s rotation. This study has the potential to help scientists better understand binary and multiple star systems, specifically the formation and evolution of their planets and what this could mean for finding life beyond Earth.

For the study, the researchers examined a planet in the binary star system, nu Octantis (nu Oct), which is located approximately 22.54 parsecs (73.5 light-years) from Earth, and is comprised of a K-type star (nu Oct A) that is approximately 1.5 times as massive as our Sun and a smaller star (nu Oct B) that is half as massive as our Sun. The planet—designated as nu Oct A b as it orbits nu Oct A—is estimated to be approximately 2.19 Jupiter masses while orbiting at approximately 1.24 astronomical units (AU) from its host star with an orbital period of approximately 402 days.

The researchers obtained radial velocity measurements from the European Southern Observatory (ESO)’s HARPS spectrograph to ascertain why nu Oct A b orbits at the distance it does, with past studies hypothesizing that it has a retrograde orbit due to its large orbital distance. In the end, not only did the researchers confirm that nu Oct A b has a retrograde orbit, but they also discovered that the smaller star in the system is a white dwarf, which are incredibly dense stars approximately the size of Earth that were once larger stars. For context, our Sun will eventually become a white dwarf star billions of years from now. Both the retrograde orbit of nu Oct A b and the white dwarf conformation of nu Oct B enabled the researchers to learn more about the system’s history.

“We found that the system is about 2.9 billion years old and that nu Oct B was initially about 2.4 times the mass of the Sun and evolved to a white dwarf about 2 billion years ago,” said Ho Wan Cheng, who is from The University of Hong Kong and lead author of the study. “Our analysis showed that the planet could not have formed around nu Oct A at the same time as the stars.”

In addition to the system’s age and stellar history, the researchers suggest two scenarios for the formation of nu Oct A b: a) It formed in a debris disk that was created from nu Oct B becoming a white dwarf, and b) It was initially in a normal orbit around the binary system (also called prograde) and was captured by nu Oct A’s gravity.

As noted, what makes this planet unique is its retrograde orbit. While Venus and Uranus in our solar system have retrograde rotations, they still exhibit prograde orbits. Therefore, the retrograde orbit of nu Oct A b could help scientists better understand the formation and evolution of exoplanets, and specifically within binary or multiple star systems. The closest multiple star system to Earth is the triple-star system, Alpha Centauri, which is located approximately 4.37 light-years from Earth and is also the closest star system, as well. While that system contains one (unconfirmed) rocky exoplanet, it exhibits a prograde orbit. There are currently only two other exoplanets that have retrograde orbits, HAT-P-7b and WASP-17b, which are part of a triple-star system and single star system, respectively.

What new discoveries about binary star systems and planetary formation and evolution will researchers make in the coming years and decades? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!

GW190814’s gravitational waves suggest a hidden supermassive black hole nearby. The finding reshapes how binary black holes may form.

Binary black holes are already among the universe’s most extraordinary phenomena, but scientists at the Shanghai Astronomical Observatory (SHAO) of the Chinese Academy of Sciences have uncovered evidence suggesting they might not exist in isolation. Instead, some of these systems could be influenced by an even more enigmatic presence—a massive companion hidden nearby.

A research group led by Dr. Wenbiao Han at SHAO recently reported strong indications that the binary black hole merger event GW190814 likely unfolded within the gravitational influence of a third compact object, which may have been a supermassive black hole.

This finding, recently published in The Astrophysical Journal Letters, provides new clues to unraveling the mystery of binary black hole formation.

Gravitational wave events and open questions

Since gravitational waves were first detected in 2015, the LIGO-Virgo-KAGRA collaboration has recorded more than 100 such events, the majority arising from binary black hole mergers. These discoveries have greatly advanced knowledge of the physics governing black hole mergers, though the processes driving their origin and development are still not fully understood.

Dr. Han’s group had earlier introduced the “b-EMRI” model, which describes a scenario where a supermassive black hole captures a binary black hole, forming a hierarchical triple system. In this configuration, the binary pair orbits the supermassive black hole, producing gravitational waves across several frequency ranges. The model was later featured in LISA’s white paper and identified as a unique target for China’s upcoming space-based gravitational wave observatories. Since then, the researchers have been searching LIGO-Virgo data for signs of mergers taking place near supermassive black holes.

Investigating GW190814’s unusual pairing

When analyzing the event GW190814, the team noted that its two merging black holes had a strikingly uneven mass ratio, close to 10:1. According to co-author Dr. Shucheng Yang, such an imbalance points to the likelihood that the pair once belonged to a triple system with a supermassive black hole, which slowly drew them together through gravitational interactions. Another possibility is that they developed within the accretion disk of an active galactic nucleus, brought together by the gravitational pull of nearby compact objects until they eventually merged.

The researchers observed that if a binary black hole merges near a third compact object, the orbital motion around the third object would produce a line-of-sight acceleration—an acceleration along the observer’s line of sight. This acceleration would alter the gravitational wave frequency through the Doppler effect, leaving a distinct “fingerprint” in the signal.

Detecting line-of-sight acceleration

To detect this signature, they developed a gravitational waveform template incorporating line-of-sight acceleration and applied Bayesian inference to analyze several high signal-to-noise binary black hole events. The results showed that for GW190814, the model with line-of-sight acceleration significantly outperformed the traditional “isolated binary black hole” model. The line-of-sight acceleration was estimated at approximately 0.002 c s-1 (90% confidence level, where *c* is the speed of light), with a Bayesian factor (a measure of model credibility) of 58:1, strongly supporting the conclusion that line-of-sight acceleration was present.

“This is the first international discovery of clear evidence for a third compact object in a binary black hole merger event,” said Dr. HAN. “It reveals that the binary black holes in GW190814 may not have formed in isolation but were part of a more complex gravitational system, offering significant insights into the formation pathways of binary black holes.”

With the next generation of ground-based gravitational wave detectors (e.g., Einstein Telescope, Cosmic Explorer) and space-based detectors (e.g., LISA, Taiji, TianQin) coming online, scientists will be able to capture subtle variations in gravitational wave signals with even greater precision. Future observations may reveal more events like GW190814, helping humanity better understand the formation and evolution of binary black holes.

Reference: “Indication for a Compact Object Next to a LIGO–Virgo Binary Black Hole Merger” by Shu-Cheng Yang, Wen-Biao Han, Hiromichi Tagawa, Song Li and Chen Zhang, 21 July 2025, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/adeaad

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