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The Universe Is Ringing

How gravitational waves from colliding black holes are opening an entirely new way of exploring the cosmos

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The Gravitational-Wave Transient Catalog 4.0, pictured, is a record of cosmic mergers detected between 2015 and 2024 by the LIGO, Virgo, and KAGRA gravitational wave observatories. Each panel is a time and frequency signature of an individual event — the merger of two black holes, two neutron stars, or one of each, somewhere out in the cosmos. Credit: Ryan Nowicki / Bill Smith / Karan Jani

More than a century after Albert Einstein predicted them, gravitational waves are transforming astronomy. Ripples in space-time produced by colliding black holes and neutron stars are now being detected routinely, revealing a universe filled with violent mergers and cosmic echoes that have travelled billions of years to reach Earth.

A Ripple Across the Cosmos

When the densest objects in the universe collide, the impact does not simply end with the destruction or merger of stars. It sends ripples through the very fabric of space and time.

These ripples—known as gravitational waves—spread outward at the speed of light, crossing galaxies and cosmic voids for millions or even billions of years. By the time they reach Earth, they are unimaginably faint distortions of space itself.

Yet scientists have learned how to detect them.

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Image by Gerd Altmann from Pixabay

A global network of observatories now monitors these tiny disturbances: the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States, the Virgo detector in Italy, and the Kamioka Gravitational Wave Detector (KAGRA) in Japan. Together, these instruments form one of the most sensitive scientific experiments ever constructed, capable of detecting distortions smaller than the width of a proton.

Through them, astronomers have begun to “listen” to the universe.

And what they are hearing is astonishing.

A Universe Filled with Collisions

The LIGO–Virgo–KAGRA (LVK) Collaboration has now released the latest compilation of gravitational-wave detections, to appear in a special issue of Astrophysical Journal Letters. The findings suggest that the cosmos is reverberating with collisions far more frequently than scientists once imagined.

The newly released Gravitational-Wave Transient Catalog-4.0 (GWTC-4) includes detections from part of the observatories’ fourth observing run, conducted between May 2023 and January 2024.

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In just nine months, the detectors recorded 128 new gravitational-wave candidates—signals that likely originated from extreme astrophysical events occurring hundreds of millions or billions of light-years away.

This newest batch more than doubles the size of the gravitational-wave catalog, which previously contained 90 candidates from earlier observing runs.

“The beautiful science that we are able to do with this catalog is enabled by significant improvements in the sensitivity of the gravitational-wave detectors as well as more powerful analysis techniques,” says Nergis Mavalvala, a member of the LVK collaboration and dean of the MIT School of Science.

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Albert Einstein /Credit: Wikipedia

What began in 2015 with the first historic detection has now become a steady stream of discoveries.

“In the past decade, gravitational wave astronomy has progressed from the first detection to the observation of hundreds of black hole mergers,” says Stephen Fairhurst, professor at Cardiff University and spokesperson for the LIGO Scientific Collaboration. “These observations enable us to better understand how black holes form from the collapse of massive stars, probe the cosmological evolution of the universe and provide increasingly rigorous confirmations of the theory of general relativity.”

When Black Holes Dance

Most gravitational waves detected so far originate from binary black holes—pairs of black holes locked in orbit around each other.

Over time, gravity draws them closer together. As they spiral inward, they release enormous amounts of energy in the form of gravitational waves. In the final fraction of a second, the two objects merge in a titanic collision, forming a single, larger black hole.

These cosmic dances are among the most energetic events in the universe.

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Black holes themselves are born when massive stars collapse at the end of their lives, compressing enormous amounts of matter into regions so dense that not even light can escape.

Many form in pairs. When they eventually collide, the event sends gravitational waves surging through space.

The first such detection, announced in 2016, confirmed a century-old prediction of Einstein’s theory of general relativity. Since then, dozens—and now hundreds—of similar events have been observed.

But the latest catalog shows that the universe is far more diverse than scientists once believed.

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Pushing the Edges of Black Hole Physics

The newly detected signals reveal a remarkable variety of cosmic systems.

Among them are the heaviest black hole binaries ever detected, systems where the masses of the two black holes are strikingly unequal, and pairs spinning at astonishing speeds.

“The message from this catalog is: We are expanding into new parts of what we call ‘parameter space’ and a whole new variety of black holes,” says Daniel Williams, a research fellow at the University of Glasgow. “We are really pushing the edges, and are seeing things that are more massive, spinning faster, and are more astrophysically interesting and unusual.”

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Image by Iris,Helen,silvy from Pixabay

One particularly dramatic signal—GW231123_135430—appears to have originated from two enormous black holes, each roughly 130 times the mass of the Sun. Most previously observed mergers involved black holes closer to 30 solar masses.

The extraordinary size of these objects suggests they may themselves have formed from earlier black hole mergers—a kind of cosmic generational chain.

Another remarkable event, GW231028_153006, revealed a binary in which both black holes are spinning at around 40 percent of the speed of light.

And in GW231118_005626, scientists detected an unusually uneven pair where one black hole is roughly twice as massive as the other.

“One of the striking things about our collection of black holes is their broad range of properties,” says Jack Heinzel, an MIT graduate student who contributed to the catalog’s analysis. “Some of them are over 100 times the mass of our sun, others are as small as only a few times the mass of the sun. Some black holes are rapidly spinning, others have no measurable spin.”

“We still don’t completely understand how black holes form in the universe,” he adds, “but our observations offer a crucial insight into these questions.”

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Catching a Whisper in Space-Time

Detecting gravitational waves requires extraordinary precision.

The observatories use L-shaped interferometers with arms several kilometers long. Laser beams travel down these tunnels and reflect back to their source.

If a gravitational wave passes through the detector, it slightly stretches one arm while compressing the other, changing the distance the light travels by an incredibly tiny amount.

These changes can be smaller than one-thousandth the diameter of a proton.

Even with such advanced technology, detections remain unpredictable.

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Image by Stefan Keller from Pixabay

“You can’t ever predict when a gravitational wave is going to come into your detector,” says Amanda Baylor, a graduate student at the University of Wisconsin–Milwaukee who worked on the signal search. “We could have five detections in one day, or one detection every 20 days. The universe is just so random.”

Recent upgrades have dramatically improved the detectors’ reach. LIGO can now detect signals from neutron star collisions up to one billion light-years away, and black hole mergers far beyond that.

Testing Einstein’s Ultimate Theory

Gravitational waves are not only revealing spectacular cosmic events. They are also providing some of the most extreme tests ever conducted of Einstein’s theory of general relativity.

Black holes themselves are one of the most extraordinary predictions of the theory.

“Black holes are one of the most iconic and mind-bending predictions of general relativity,” says Aaron Zimmerman, associate professor of physics at the University of Texas at Austin.

When two black holes collide, he explains, they “shake up space and time more intensely than almost any other process we can imagine observing.”

One particularly powerful signal—GW230814_230901—allowed scientists to analyze the structure of the gravitational wave in exceptional detail.

“So far, the theory is passing all our tests,” Zimmerman says. “But we’re also learning that we have to make even more accurate predictions to keep up with all the data the universe is giving us.”

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Measuring the Expansion of the Universe

Gravitational waves are also becoming powerful tools for answering one of cosmology’s biggest questions: how fast the universe is expanding.

Astronomers measure this expansion using the Hubble constant, but different methods have produced conflicting results.

Gravitational waves offer an independent approach.

“Merging black holes have a really unique property: We can tell how far away they are from Earth just from analyzing their signals,” says Rachel Gray, a lecturer at the University of Glasgow.

“So, every merging black hole gives us a measurement of the Hubble constant, and by combining all of the gravitational wave sources together, we can vastly improve how accurate this measurement is.”

Using the current gravitational-wave catalog, scientists estimate that the universe is expanding at roughly 76 kilometers per second per megaparsec.

For now, the uncertainty remains large—but future detections could sharpen the measurement significantly.

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Image by Johnson Martin from Pixabay

Listening to the Future

Only a decade ago, gravitational waves were purely theoretical signals.

Today, they are transforming astronomy.

With every new detection, scientists gain another glimpse into the hidden life of the universe: the birth of black holes, the evolution of galaxies, and the behavior of gravity under the most extreme conditions imaginable.

“Each new gravitational-wave detection allows us to unlock another piece of the universe’s puzzle in ways we couldn’t just a decade ago,” says Lucy Thomas, a postdoctoral researcher at the Caltech LIGO Lab.

“It’s incredibly exciting to think about what astrophysical mysteries and surprises we can uncover with future observing runs.”

The instruments on Earth are quiet, their lasers moving silently down vacuum tunnels. But far beyond our galaxy, black holes continue to collide.

And with each collision, the universe sends out another ripple—another echo across the cosmos—waiting for us to hear it.

EP Staff is the editorial team at EdPublica, an independent media organisation focused on science, education, environment and public policy. The team produces evidence-based news, features, explainers and analysis on issues that shape society and everyday life.

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Space & Physics

India’s New Satellite Will Be Tested During Disasters

India’s latest Earth-observation satellite, EOS-05, could give disaster agencies a broader and more frequent view of floods, landslides and other hazards. But its real value will depend on how quickly satellite data can be turned into information that helps authorities act on the ground.

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GSLV-F17 rocket carrying ISRO’s EOS-05 Earth-observation satellite at the launch pad
ISRO’s GSLV-F17 carrying the EOS-05 Earth-observation satellite stands ready for launch, marking India’s first imaging satellite mission to geosynchronous orbit. Image credit: ISRO

When a flood spreads or a landslide cuts off a village, one of the first things authorities need is a clear picture of what has happened. India’s newest Earth-observation satellite could help close part of that information gap. Which areas are under water? Which roads are still open? Where are people stranded? Ground teams may be unable to reach affected areas, while conditions can change faster than assessments can be completed.

On September 4, the Indian Space Research Organisation (ISRO) successfully launched GSLV-F17 carrying EOS-05, which ISRO describes as India’s first imaging satellite designed for geosynchronous orbit. The satellite was placed into a sub-geosynchronous transfer orbit before its subsequent orbital operations.

The launch is a technological milestone. But its larger significance may be in how India uses the satellite once it is in operation.

Seeing a Disaster From Above

Earth-observation data already play a role in India’s disaster management. ISRO’s systems are used for applications including flood mapping, damage assessment and emergency management, while the National Database for Emergency Management brings together geospatial information for disaster agencies.

EOS-05 adds a different capability because of its orbit. A geosynchronous satellite can repeatedly observe a broad region as the Earth rotates. That makes it possible to monitor large areas without relying entirely on a satellite making another pass over the location.

During a flood, that could help authorities understand the extent of inundation. After a landslide, imagery could contribute to assessing affected terrain. The same Earth-observation infrastructure has applications in agriculture, water resources, forestry and urban planning. But the satellite itself is not the solution.

The Real Test is Speed

There is a long distance between an image captured in space and a decision made in a district control room. Data have to be received, processed and interpreted. The resulting information has to reach officials and emergency teams quickly enough to matter. That is particularly important when disasters are unfolding by the hour.

A satellite cannot rescue people or reopen a blocked road. What it can do is help authorities decide where those efforts are most urgently needed.

That distinction is important. The value of space technology in disaster management is not simply that it produces better images. It is that those images can potentially reduce the time needed to understand what is happening on the ground.

From Mapping Damage to Managing Risk

India’s disaster landscape makes that capability increasingly relevant. Floods can spread across districts, while landslides can isolate mountain communities with little warning. Cyclones, forest fires and extreme rainfall can also leave authorities trying to assess large areas at once.

Satellite observation cannot predict every such event. But combined with weather forecasts, river-level data, ground reports and geographic information, it can provide a fuller picture of how a disaster is unfolding. That is where EOS-05 could become more than another addition to India’s satellite fleet.

The real measure of its success will not be the launch itself, or even the quality of the images it produces. It will be whether those images reach the right people quickly enough to change what happens on the ground. Because in a disaster, seeing more is useful only if it helps authorities act faster and act in the right place.

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India’s Moonshot Moment: Can New Delhi Turn Orbit Into Influence

India’s space mission is entering a new era, from Gaganyaan and space stations to private startups, space diplomacy and national security.

Anoop Krishnan H

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Gaganyaan is only the beginning. India’s space mission faces new opportunities and challenges as human spaceflight
The Gaganyaan capsule, illustrated: India's answer to six decades of human spaceflight by other powers. Illustration: Edpublica

Gaganyaan is only the beginning. India’s space mission faces new opportunities and challenges as human spaceflight, diplomacy, private industry and security reshape its ambitions beyond Earth.

Indian human space programme Gaganyaan is mooted by Indian Space Research Organisation. This ambitious space mission aims to send Indian astronauts in Outer Space indigenously by the proactive leadership of the Indian government.  India as a leading space power of the world aims to demonstrate her space capabilities and research in the final frontier. The Gaganyaan mission is the dream of 1.4 billion Indians. The programme will be initiated in 2027 creating a historic mark in the collective space exploration journeys. This is a stepping stone as NASA is envisioning to make Moon as the next base for active space programmes by 2030.

According to NASA this spectacular feat will be achieved soon within 3 years.  NASA has asked India’s ISRO to join for the permanent Lunar base in the south pole of Moon. Here comes the significance of Indo-US space partnership and how India will navigate through the space diplomacy keeping in mind of Indian dream of Bharatiya Antariksh Station and the long lasting commitment to strategic autonomy and an independent foreign policy. India already signed the Artemis accords in June 2023. If India is ready to be part of this initiative, it will mark the beginning of a new era in India-United States space cooperation. The question is how India will navigate this process, protecting its sovereignty and national interest while engaging with NASA to help build a new civilisation of space travellers on the lunar surface. According to media reports  India’s spectacular success with the Chandrayaan missions has led the United States to choose India as a natural partner, inviting it to join space exploration programmes on the Moon.

India’s Space Mission: The Next Frontier of Global Power

india space milestones timeline 2
Tracing India’s human spaceflight and space-policy milestones from Rakesh Sharma in 1984 through to the planned Gaganyaan (2027) and Bharatiya Antariksh Station (2035) — achieved milestones in blue, planned ones in amber.

The Gaganyaan mission is significant for strengthening Indian space station’s vision.  The Bharatiya Antariksh Station is an Indian space station which is a symbol of Indian space nationalism and a centre for joint research with friendly nations. India is actively pushing for space diplomacy and it is evident from the trainings received by Gaganyaan crew members. They have trained in Russia and the United States, continuing India’s commitment to strong bilateral ties with both Cold War-era rivals. Space exploration and travel are combined with diplomacy, as Indian foreign policy in a multipolar world order pushes for strong partnerships with both Russia and the United States.

Indian Air Force veteran Wing Commander Rakesh Sharma was the first Indian cosmonaut to reach the final frontier, in a Soviet space mission. Following this historic feat, Kalpana Chawla and Sunita Williams travelled to outer space on American missions. Recently, Group Captain Shubhanshu Shukla represented India in the Axiom mission successfully travelling to International Space Station and returned safely as a national hero. He is also part of the Gaganyaan mission. Colonel Anil Menon, who is part of the US Space Force, is also now in outer space. He has strong Indian connections, making him the first astronaut with roots in Kerala to explore the domain of outer space.

With privatisation in outer space in India, Skyroot Aerospace, a private company based in Hyderabad, successfully launched Vikram-1 rocket to low Earth orbit. Thus India is taking leverage of the infinite possibilities chasing stars and galaxies. Indian space ambitions are at a historic juncture now, with over 400 private Space  startups. Another mission is aiming for a reusable re-entry vehicle, targeted for launch in 2027, building on ISRO’s success with the Pushpak mission, the Reusable Launch Vehicle Landing Experiment, in 2024.

India's space mission. Gaganyaan crew module mounted on the test vehicle during ISRO's TV-D1 mission preparations.
Gaganyaan crew module and test vehicle used for ISRO’s TV-D1 abort test mission in 2023. Image Credit: Indian Space Research Organisation (ISRO), Government of India

However, there are concerns in India’s space sector, with many ISRO scientists seeking early retirement. The efficiency of major projects like Aditya and Gaganyaan should not be affected by this. Former ISRO Chairman G Madhavan Nair shared his concerns with the media about bureaucratisation within the organisation. ISRO is a symbol of India’s space story which is filled with resilience and strength of great visionary leaders like Dr Vikram Sarabhai and Dr APJ Abdul Kalam. Unfortunately, there have been budgetary cuts to major ISRO space projects. The government’s focus on Viksit Bharat, a holistically developed India, is only possible with investment in science and technology, and in-depth research in the domain of outer space.

Outer space is militarised, and the race for resource nationalism is a reality. For India to emerge as a global power, investment in space exploration is inevitable. Nations are increasingly aware of the strategic use of outer space for securing national interests. Satellites with civilian and national security purposes are critical assets of any nation. India too has many civilian and strategic assets in outer space, and protecting these is the responsibility of the government. The anti-satellite test Mission Shakti is a milestone demonstrating India’s hard-power capabilities in outer space. Some nations have capabilities such as laser-guided weapons, which can disable or destroy an enemy’s assets during conflict. Space is a key domain for ensuring seamless communication and intelligence-sharing during both war and peace.

Intelligence and surveillance are key factors in winning the wars of the present and future. The dominance in space technology and information superiority will determine the victories of nations fighting for their national interest.   

In India, the share of higher education in the annual budgetary allocation remains low. A young generation passionate to explore arenas of space science is to be inculcated with the right mindset. Allocation of funds in education sector is a key requirement for building a strong India with educated and skilled youth. ISRO’s active collaboration with 100 Atal Tinkering Labs is a positive step in inculcating the spirit of scientific enquiry at the grassroots level. Support and encouragement for students in the creative arts and sciences is the need of the hour. Atal Tinkering Labs and India’s startup ecosystem can achieve greater synergy, ensuring a seamless transition from school life to entrepreneurship, from plan to execution.

Human activity has actively degraded the ecosystem, impacting life on both land and water. Now, with active competition in the arena of outer space, space debris is a serious global security challenge. This debris travels swiftly in outer space, damaging active space assets including civilian and defence satellites. The young budding scientists of India need to re-invent and discover practical solutions to the pressing global challenge of space debris and work with relentless passion for making a strong and stable India.

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Meteorite Dust Reveals Evidence of Magnetic Field in the Young Solar System

A magnetic field in the early solar system has been detected in ancient meteorite grains, offering evidence that magnetism helped shape the young sun.

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A magnetic field in the early solar system

Ancient grains in an Antarctic meteorite reveal evidence of a magnetic field in early solar system, suggesting magnetism helped shape the young sun

Tiny mineral grains preserved inside an ancient meteorite have recorded evidence of a magnetic field that existed during the earliest stages of the solar system, suggesting that magnetism, alongside gravity, helped shape the young sun and its surrounding disk of gas and dust.

Ancient Meteorite Records Reveal a Magnetic Field in the Early Solar System

Scientists at the Massachusetts Institute of Technology (MIT) examined microscopic grains in a meteorite recovered from Antarctica and found traces of ancient magnetism dating to the first 200,000 years of solar system history. The findings provide what researchers describe as the earliest known evidence of a magnetic field in the infant solar system.

The study, published in the Proceedings of the National Academy of Sciences, challenges the view that gravity alone drove the transformation of the early solar system from a cloud of gas and dust into a flattened disk that eventually produced the sun and planets.

“This transition, from a spherical cloud to a protoplanetary disk, is one of the most significant events in all of solar system history,” said Benjamin Weiss, professor of Earth and Planetary Sciences at MIT, in a statement issued. Measurements from the study, he said, indicate that magnetism likely played a role.

Magnetic records preserved in meteorite grains

The researchers studied DOM 08006, a primitive meteorite discovered in 2008 in the Dominion Range of Antarctica. The meteorite contains calcium-aluminum-rich inclusions, or CAIs, which formed during the earliest period of solar system development.

CAIs are among the oldest known solid materials from the solar system. Some of the grains contain magnetic minerals that can preserve the imprint of a magnetic field present when they formed.

The team isolated tiny grains from the meteorite and subjected them to a series of tests to determine whether they retained remanent magnetisation — a lasting record of an earlier magnetic field.

The researchers found evidence of a magnetic field with an estimated strength of about 150 to 600 microteslas. That is roughly three to 12 times stronger than Earth’s magnetic field today.

The preservation of these records was possible because DOM 08006 appears to have undergone relatively little alteration during its long history.

“Other meteorites went through many different processes over this 4.5 billion year history,” Weiss said. “But somehow, DOM has experienced less alteration than any other meteorite.”

Magnetism before the planets

Scientists already had evidence of magnetic fields in the solar system several million years after its formation, when the sun had formed and the planets were beginning to take shape.

The new measurements push that evidence much further back — to a period when the solar system was still a collapsing cloud of gas and dust and the sun itself was beginning to form.

In the early solar system, electrically charged particles moving through the developing disk could have generated a magnetic field. That field may then have influenced the movement of gas and material towards the central star.

The researchers argue that magnetism therefore needs to be considered alongside gravity when reconstructing how the early solar system evolved.

“We think these kinds of magnetic fields were helping to move gas from the protoplanetary disk, in toward this central star, the sun,” said Cauê Borlina, the study’s first author and now an assistant professor at Purdue University.

The findings do not replace gravity as the main force shaping the early solar system. Instead, they suggest that magnetic fields were another important part of the physical processes that brought material together and helped the young sun grow.

The study was led by Borlina, with Weiss, Elias Mansbach and Nilanjan Chatterjee of MIT, along with researchers from Tsinghua University, the University of Cambridge, Caltech and the University of California, Los Angeles

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