̽��ֱ�� of Cambridge - Andy Fabian

Professor Andrew Fabian awarded Kavli Prize

sc604 — Wed, 27 May 2020 13:15:00 +0000

Professor Fabian is one of seven scientists from five countries honoured for breakthrough discoveries in astrophysics, nanoscience and neuroscience.

̽��ֱ��Norwegian Academy of Science and Letters today announced the 2020 Kavli Prize Laureates in the fields of astrophysics, nanoscience and neuroscience. This year’s Kavli Prize honours scientists whose research has transformed our understanding of the very big, the very small and the very complex. ̽��ֱ��laureates in each field will share $1million USD.

“ ̽��ֱ��2020 Kavli Prize Laureates represent truly pioneering science, the kind of science which will benefit humanity in a profound way, inspiring both current and future generations,” says Hans Petter Graver, president of ̽��ֱ��Norwegian Academy of Science and Letters.

The Kavli Prize in Astrophysics is awarded to astronomer and astrophysicist Andrew Fabian for his pioneering research and persistence in pursuing the mystery of how black holes influence their surrounding galaxies on both large and small scales. For decades, researchers have pondered the mechanics and physical processes of galaxies, and many have made discoveries that point to aspects of their inner workings; yet none has the unique vantage point of Fabian: to take a multi-scale understanding and systematically know where to look to put the pieces of the puzzle together and create the bigger picture of this vast ecosystem.

In the current cosmological paradigm, the universe is a ‘living’ system, in which the flows of gas into galaxies and black holes at their centres, and the subsequent release of energy back into the galaxies and their surroundings, all play vital roles. As the darkest objects in the universe, black holes are observed as their gravity attracts surrounding gas, dust and stars, which swirl into them at high velocities, creating intense radiation, much of it X-rays. Observational X-ray astronomy opened up access to view these and other extremely hot and energetic components of the universe, providing stunning evidence for these processes at work, unveiling how the major constituents of the universe can profoundly influence its overall evolution.

Professor Fabian employs X-ray astronomy to explore the physics of the universe. His body of work – from understanding large-scale galactic evolution to the physics of black holes at the centres of galaxies – enabled him to make connections between local conditions around supermassive black holes and the larger gas flows within and between galaxies. This research provided evidence that supermassive black holes at the heart of galaxies are the engines that drive the flow of hot gas out of the galaxy, redistributing energy through the universe and providing the building blocks for future galaxy formation.

“Andrew Fabian is one of the most prolific and influential astronomers of our time,” said Viggo Hansteen, chair of the Kavli Prize Committee in Astrophysics. “His research, breadth of knowledge and insights into the universe provided the essential physical understanding of how disparate phenomena in this ecosystem are interconnected.”

This year’s Kavli Prize Laureates also include Professor Ondrej L Krivanek, an alumnus of Trinity College, Cambridge, who is now based in the United States. Professor Krivanek completed his PhD at the Cavendish Laboratory in 1975 under the supervision of Professor Archie Howie. He was awarded the Kavli Prize in Nanoscience, along with Harald Rose (Germany), Maximilian Haider (Austria), Knut Urban (Germany). Their work enabled humanity to see the structure and chemical composition of materials in three dimensions on unprecedentedly short length scales.

̽��ֱ��Kavli Prize is a partnership between ̽��ֱ��Norwegian Academy of Science and Letters, the Norwegian Ministry of Education and Research and ̽��ֱ��Kavli Foundation (US). ̽��ֱ��Kavli Prize honours scientists for breakthroughs in astrophysics, nanoscience and neuroscience that transform our understanding of the very big, the very small and the very complex. Three million-dollar prizes are awarded every other year in each of the three fields. ̽��ֱ��Norwegian Academy of Science and Letters selects the laureates based on recommendations from three prize committees whose members are nominated by ̽��ֱ��Chinese Academy of Sciences, ̽��ֱ��French Academy of Sciences, ̽��ֱ��Max Planck Society of Germany, ̽��ֱ��U.S. National Academy of Sciences and ̽��ֱ��UK’s Royal Society. First awarded in 2008, ̽��ֱ��Kavli Prize has honoured 54 scientists from 13 countries – Austria, Czech Republic, France, Germany, Japan, Lithuania, ̽��ֱ��Netherlands, Norway, Russia, Sweden, Switzerland, the United Kingdom and the United States.

̽��ֱ��Kavli Prize Laureates are typically celebrated in Oslo, Norway, in a ceremony presided over by His Majesty King Harald followed by a banquet at the Oslo City Hall, the venue of the Nobel Peace Prize. Due to the COVID-19 pandemic, this year’s award ceremony is postponed and will be held together with the 2022 award ceremony in September 2022.

Professor Andrew Fabian from Cambridge's Institute of Astronomy has been awarded the 2020 Kavli Prize in Astrophysics, one of the world's most prestigious science prizes.

Sam Fabian

Professor Andrew Fabian

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A force to be reckoned with

sc604 — Mon, 27 Nov 2017 16:04:01 +0000

Gravity is one of the universe's great mysteries. We decided to find out why.

Think you know what gravity is? Think again. New research is revealing how little we know about this most mysterious of forces.

Rapid changes point to origin of ultra-fast black hole winds

ps748 — Wed, 01 Mar 2017 18:08:32 +0000

Outflowing gas is a common features of the supermassive black holes that reside at the centre of large galaxies. Often millions of times more massive than the Sun, these black holes feed off the surrounding gas that swirls around them. Space telescopes observe this as a bright light from the innermost part of the disc around the black hole.

Occasionally the black holes consume too much gas and release an ultra-fast wind. These winds are an important characteristic to study because they could have a strong influence on regulating the growth of the host galaxy by clearing the surrounding gas away and therefore suppressing the birth of stars.

Using ESA’s XMM-Newton and NASA’s NuStar telescopes, scientists have now made the most detailed observation yet of such an outflow. ̽��ֱ��winds recorded from the black hole reach 71,000 km/s – a quarter of the speed of light – putting it in the top 5% of fastest known black hole winds.

XMM-Newton focused on the black hole for 17 consecutive days, revealing the extremely variable nature of the winds.

“We often only have one observation of a particular object, then several months or even years later we observe it again and see if there’s been a change,” says Dr Michael Parker of the Institute of Astronomy at the ̽��ֱ�� of Cambridge, UK, lead author on a paper published in Nature this week which describes the discovery.

“Thanks to this long observation campaign, we observed changes in the winds on a timescale of less than an hour for the first time.”

̽��ֱ��changes were seen in the increasing temperature of the winds, a signature of their response to greater X-ray emission from the disc right next to the black hole.

Furthermore, the observations also revealed changes to the chemical fingerprints of the outflowing gas: as the X-ray emission increased, it stripped electrons in the wind from their atoms, erasing the wind signatures seen in the data.

“ ̽��ֱ��chemical fingerprints of the wind changed with the strength of the X-rays in less than an hour, hundreds of times faster than ever seen before,” says co-author Professor Andrew Fabian, also from the Institute of Astronomy, and principal investigator on the project.

“It allows us to link the X-ray emission arising from the material falling into the black hole, to the variability of the outflowing wind farther away.”

Dr Parker adds: “Black hole winds are one of the mechanisms for feedback, where the energy coming out from the black hole regulates the growth of the host galaxy. Understanding these winds is crucial to understanding how galaxies, including our own, grow.”

Michael Parker et al: " ̽��ֱ��response of relativistic outflowing gas to the inner accretion disk of a black hole" Nature 2 March 2017

Adapted from a press release by the European Space Agency

Astronomers have made the most detailed observation yet of an ultra-fast wind emanating from a Black Hole at a quarter of the speed of light. Using the European Space Agency (ESA)’s XMM-Newton and NASA’s NuSTAR telescopes, the scientists observed the phenomenon in an active galaxy known as IRAS 13224-3809.

Understanding these winds is crucial to understanding how galaxies, including our own, grow

Dr Michael Parker

European Space Agency (ESA)

Artist's impression of the winds emanating from the supermassive black hole

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New exoplanet think tank will ask the big questions about extra-terrestrial worlds

sc604 — Mon, 05 Sep 2016 08:44:25 +0000

With funding from ̽��ֱ��Kavli Foundation, the think tank will bring together some of the major researchers in exoplanetary science – arguably the most exciting field in modern astronomy – for a series of annual meetings to address the biggest questions in this field which humanity could conceivably answer in the next decade.

“We’re really at the frontier in exoplanet research,” said Dr Nikku Madhusudhan of Cambridge’s Institute of Astronomy, who is leading the think tank. “ ̽��ֱ��pace of new discoveries is incredible – it really feels like anything can be discovered any moment in our exploration of extra-terrestrial worlds. By bringing together some of the best minds in this field we aim to consolidate our collective wisdom and address the biggest questions in this field that humanity can ask and answer at this time.”

Tremendous advances have been made in the study of exoplanets since the first such planet was discovered around a sun-like star in 1995 by the Cavendish Laboratory’s Professor Didier Queloz. Just last month, a potentially habitable world was discovered in our own neighbourhood, orbiting Proxima Centauri, the nearest star to the sun.

However, there are still plenty questions to be answered, such as whether we’re capable of detecting signatures of life on other planets within the next ten years, what the best strategies are to find habitable planets, how diverse are planets and their atmospheres, and how planets form in the first place.

With at least four space missions and numerous large ground-based facilities scheduled to become operational in the next decade, exoplanetary scientists will be able to detect more and more exoplanets, and will also have the ability to conduct detailed studies of their atmospheres, interiors, and formation conditions. At the same time, major developments are expected in all aspects of exoplanetary theory and data interpretation.

In order to make these major advances in the field, new interdisciplinary approaches are required. Additionally, as new scientific questions and areas emerge at an increasingly fast pace, there is a need for a focused forum where emerging questions in frontier areas of the field can be discussed. “Given the exciting advancements in exoplanetary science now is the right time to assess the state of the field and the scientific challenges and opportunities on the horizon,” said Professor Andy Fabian, director of the Institute of Astronomy at Cambridge.

̽��ֱ��think tank will operate in the form of a yearly Exoplanet Symposium series which will be focused on addressing pressing questions in exoplanetary science. One emerging area or theme in exoplanetary science will be chosen each year based on its critical importance to the advancement of the field, relevance to existing or imminent observational facilities, need for an interdisciplinary approach, and/or scope for fundamental breakthroughs.

About 30 experts in the field from around the world will discuss outstanding questions, new pathways, interdisciplinary synergies, and strategic actions that could benefit the exoplanet research community.

̽��ֱ��inaugural symposium, “Kavli ExoFrontiers 2016”, is being held this week in Cambridge. ̽��ֱ��goal of this first symposium is to bring together experts from different areas of exoplanetary science to share their visions about the most pressing questions and future outlook of their respective areas. These visions will help provide both a broad outlook of the field and identify the ten most important questions in the field that could be addressed within the next decade. “We hope the think tank will provide a platform for new breakthroughs in the field through interdisciplinary and international efforts while bringing the most important scientific questions of our time to the fore,” said Madhusudhan. “We are in the golden age of exoplanetary science.”

More information about the Kavli ExoFrontiers 2016 Symposium is available at: www.ast.cam.ac.uk/meetings/2016/kavli.exofrontiers.2016.symposium

An international exoplanet ‘think tank’ is meeting this week in Cambridge to deliberate on the ten most important questions that humanity could answer in the next decade about planets outside our solar system.

We’re really at the frontier in exoplanet research.

Nikku Madhusudhan

ESO/M. Kornmesser

Artist’s impression of the ultracool dwarf star TRAPPIST-1 from the surface of one of its planets

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Dead satellite finds a calm centre at the heart of brightest galaxy cluster in the sky

sc604 — Wed, 06 Jul 2016 17:30:00 +0000

̽��ֱ��result, published in the journal Nature, allows the mass of the Perseus Cluster – a swarm of thousands of galaxies that spans two million light years across and is one of the most massive known objects in the universe – to be calculated more accurately than before. Once this technique can be extended to other clusters, it will allow cosmologists to use them as better probes of our models of the Universe’s evolution from the Big Bang to the present time.

Hitomi (originally known as ASTRO-H) is the sixth in a series of Japanese x-ray observatories. Led by the Japan Aerospace Exploration Agency (JAXA), it is a collaboration of over 60 institutes and 200 scientists and engineers from Japan, the US, Canada, and Europe, including from the ̽��ֱ�� of Cambridge. ̽��ֱ��spacecraft was launched on 17 February 2016 from the Tanegashima Space Center, Japan. However, JAXA announced in April that it was no longer possible to communicate with the satellite.

“Hitomi targeted the Perseus cluster just a week after it arrived in space,” said Matteo Guainazzi, the European Space Agency’s (ESA) Hitomi Resident Astronomer at the Institute of Space and Astronautical Science, Japan. “Perseus is the brightest x-ray galaxy cluster in the sky. It was therefore the best choice to fully demonstrate the power of the Soft X-ray Spectrometer (SXS), an x-ray micro-calorimeter that promised to deliver an unprecedented accuracy in the reconstruction of the energy of the incoming x-ray photons.” Waiting astronomers were not disappointed.

̽��ֱ��Hitomi collaboration found that SXS could measure the turbulence in the cluster to a precision of 10 kilometres/second. But it was the absolute velocity of the gas that took them by surprise. It was just 164 ± 10 kilometres/second. ̽��ֱ��previous best measurement for Perseus was taken with ESA’s XMM-Newton x-ray observatory. Using a different type of spectrometer, it could only constrain the speed to be lower than 500 kilometres/second.

Hitomi’s measurement is therefore much more precise than any similar measurements performed in x-rays so far. “This is due to the outstanding performance and stability of the SXS in space. This demonstrates that the technology of x-ray micro-calorimeters can yield truly transformational results,” said Guainazzi.

̽��ֱ��result indicates that the cluster gas has very little turbulent motions within. Turbulent motions in a fluid are part of our everyday life, as airplane passengers, swimmers, or parents filling a bathtub all experience. ̽��ֱ��study of such chaotic behaviour is also a powerful tool for astronomers to understand the behaviour of celestial objects.

Turbulent energy in Perseus is just four percent of the energy stored in the gas as heat. This is extraordinary considering that the active galaxy NGC 1275 sits at the heart of the cluster. It is pumping jetted energy into its surroundings, creating bubbles of extremely hot gas. It was thought that these bubbles induce turbulence, which keeps the central gas hot.

Hitomi shows that turbulent motion is almost absent from the cluster, and this gives rise to a mystery: what is keeping the cluster’s widespread gas hot?

“This result from Hitomi is telling us that in terms of how cluster cores work, we have to think very carefully about what is going on,” said the paper’s senior author Professor Andy Fabian of Cambridge’s Institute of Astronomy, and part of the Hitomi collaboration.

Fabian is working on the possibility of sound waves as the means of spreading the energy evenly throughout the gas. This is because in a sound wave, energy can be moved while the medium itself remains more or less stationary.

There are wider implications for this work too. Clusters of galaxies are the largest bound structures in the Universe. At the same time, they are also the smallest self-contained ‘boxes’. This means that matter is not flowing in or out of a cluster of galaxies. Instead, they each represent an island in which cosmic evolution has played out and been recorded.

Computer models of the expanding Universe use the distribution of cluster masses as an observational test of whether they are correct. Calculating the mass of a cluster depends upon the ratio of turbulent to quiescent gas. Any way of more accurately measuring turbulence allows better masses to be calculated, and therefore better computer models of the whole Universe to be developed.

Unfortunately, just a few weeks after the Perseus observation, a malfunction in the attitude control system put Hitomi into an uncontrollable spin that resulted in the break up and loss of the satellite.

“It is really disappointing that we have lost Hitomi and can’t go on with the programme that we had to look at many more clusters,” says Fabian.

̽��ֱ��next mission that will be capable of fully following up the Hitomi programme is ESA’s Athena, an X-ray observatory scheduled for launch in the 2020s.

“Scientifically and technically, the Hitomi results are an exciting foretaste of Athena,” said David Lumb, ESA's Athena Study Scientist. “ ̽��ֱ��demonstration of a radically new imaging spectrometer instrument concept gives huge confidence for future developments for Athena.”

Athena will have 100 times more collecting area and 100 times more pixels than Hitomi. Among the key scientific objectives of Athena are to investigate the evolution of clusters of galaxies including their interplay with energy injection from supermassive black holes.

“ ̽��ֱ��Hitomi data show the potential that will be unleashed with Athena vastly increased imaging capability and sensitivity,” said Lumb.

Reference:
Hitomi Collaboration. ‘ ̽��ֱ��quiet intracluster medium in the core of the Perseus cluster.’ Nature (2016). doi:10.1038/nature18627.

Adapted from an ESA press release.

With its very first – and last – observation, the Hitomi x-ray observatory has discovered that the gas in the Perseus cluster of galaxies is much less turbulent than expected, despite being home to NGC 1275, a highly energetic active galaxy.

This result is telling us that in terms of how cluster cores work, we have to think very carefully about what is going on.

Andy Fabian

Background: NASA/CXO; Spectrum: Hitomi Collaboration/JAXA, NASA, ESA, SRON, CSA

X-ray view of the Perseus cluster

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Galactic ‘vapour trails’ uncovered in giant cluster

fpjl2 — Fri, 20 Sep 2013 09:44:57 +0000

Unusual gas filament ‘arms’ have been found in the central region of the Coma cluster, a large collection of thousands of galaxies located about 300 million light years from Earth - and one of the largest structures in the Universe held together by gravity.

These remarkably long arms – which bear resemblance to vast galactic vapour trails - glow in X-ray light, and tell astronomers about the collisions that took place between Coma and other galaxy clusters over the last billion years.

A team of astronomers from Cambridge and the Max Planck Institute discovered the enormous X-ray vapour trails – spanning at least half a million light years – in Coma by using data from NASA’s Chandra X-ray Observatory as well as ESA’s XMM-Newton. ̽��ֱ��elongated filaments of hot gas were revealed after enhancing the detail in Chandra X-ray images, shown in purple above.

Researchers think that these arms were most likely formed when smaller galaxy clusters had their hot gas stripped away while merging with the larger Coma cluster. This would have left a trail of superheated gas behind them similar to a jet leaving behind trails of water vapour as it moves across the sky.

Coma is an unusual galaxy cluster because it contains not one, but two giant elliptical galaxies near its centre. These two giant elliptical galaxies are probably the trace remains of each of the two largest galaxies that merged with Coma in the past. There are also other signs of past collisions and mergers that the researchers were able to uncover in the data.

̽��ֱ��newly discovered X-ray arms are thought to be about 300 million years old, and they appear to have a rather smooth shape. This gives researchers some clues about the conditions of the hot gas in Coma. Most theoretical models expect that mergers between clusters like those in Coma will produce strong turbulence, like ocean water that has been churned by passing ships. Instead, the smooth shape of these lengthy arms points to a rather calm setting for the hot gas in the Coma cluster, even after many mergers.

“Coma is like a giant cosmic train wreck where several clusters have collided with each other. We hadn’t expected that these rather delicate straight filaments would survive in that environment,” said lead author Dr Jeremy Sanders, who conducted much of the research whilst at Cambridge’s Institute of Astronomy alongside Professor Andrew Fabian.

“ ̽��ֱ��existence of these long straight structures appears to point towards the centre of the Coma cluster being a much calmer environment than we had expected.”

Elongated structures of hot gas found after enhancing the detail in images taken with the Chandra (pink) and on larger scales XMM-Newton (purple) X-ray observatories

Two of the arms appear to be connected to a group of galaxies located about two million light years from the centre of Coma. One or both of the arms connects to a larger structure seen in the XMM-Newton data, and spans a distance of at least 1.5 million light years. A very thin tail also appears behind one of the galaxies in Coma. This is probably evidence of gas being stripped from a single galaxy, in addition to the groups or clusters that have merged there.

Galaxy clusters are the largest objects held together by gravity in the universe. ̽��ֱ��collisions and mergers between galaxy clusters of similar mass are the most energetic events in the nearby universe. These new results are important for understanding the physics of these enormous objects and how they grow.

Large-scale magnetic fields are likely responsible for the small amount of turbulence that is present in Coma. Estimating the amount of turbulence in a galaxy cluster has been a challenging problem for astrophysicists. Researchers have found a range of answers, some of them conflicting, and so observations of other clusters are needed.

These new results on the Coma cluster, which incorporate over six days worth of Chandra observing time, appears in the latest issue of the journal Science.

Text adapted from a NASA Chandra press release

Astronomers have discovered enormous smooth shapes that look like vapour trails in a gigantic galaxy cluster. These ‘arms’ span half a million light years and provide researchers with clues to a billion years of collisions within the “giant cosmic train wreck” of the Coma cluster.

Coma is like a giant cosmic train wreck where several clusters have collided with each other. We hadn’t expected that these rather delicate straight filaments would survive in that environment

Jeremy Sanders

NASA Chandra

Revealed elongated filaments of hot gas found after enhancing the detail in Chandra X-ray images (purple), also showing the optical light galaxies in cluster (taken from the Sloan Digital Sky Survey)

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“Echo” of light augurs new era in study of black holes

bjb42 — Thu, 31 May 2012 21:00:24 +0000

̽��ֱ��findings open up new opportunities for scientists trying to map and understand what happens on the brink of “active galactic nuclei”, or AGNs; monster black holes that exist at the heart of most big galaxies.

These black holes contain millions of times the sun’s mass. As matter streams towards them, the centre of the galaxy lights up, emitting billions of times more energy than the sun and illuminating the disk of matter that forms at the hole’s edge.

One of the most important tools for astronomers studying these black holes is something called the “iron K line”. This is a shape which appears as very distinctive X-rays created by iron atoms, which, when excited, emit energies of around 6,000 to 7,000 electron volts – several thousand times the energy in visible light.

̽��ֱ��line brightens as the result of a mysterious and intense X-ray source near to the black hole. This source shines on to the accumulated matter, causing the iron atoms to radiate their K-line energy. In effect, when the source flares, a light “echo” sweeps across the disk of matter and the iron K line lights up accordingly, after a delay corresponding to how long the X-rays took to reach the disk. ̽��ֱ��process is called relativistic reverberation.

Although observing this process carries the promise of a much better understanding of what is happening around supersized black holes, neither the European Space Agency, nor NASA, have telescopes powerful enough to spot the reverberations of single flares coming from the source.

To get round this problem, the researchers, from the Universities of Maryland and Cambridge, reasoned that it might be possible to detect the combined echoes from several flares, if a large amount of data from a particular object in space could be analysed.

This object turned out to be the galaxy NGC 4151, which is located about 45 million light-years away in the constellation Canes Venatici. ̽��ֱ��galaxy has one of the brightest AGNs in X-rays and astronomers think that it is powered by a black hole weighing 50 million solar masses. ̽��ֱ��sheer scale of this black hole suggests that it also has a large accretion disk of matter, capable of producing particularly long-lived and detectable echoes of light coming from the X-ray source.

̽��ֱ��data needed to identify the light echoes came from observations carried out using the European Space Agency’s XMM-Newton satellite. By analysing the data, the researchers were able to uncover numerous X-ray echoes, demonstrating the reality of relativistic reverberation for the first time. Their findings are published in the May 8 issue of the Monthly Notices of the Royal Astronomical Society.

̽��ֱ��study shows that the echoes lagged behind the original flares by a little more than 30 minutes. Moving at the speed of light, the X-rays associated with the echo must have travelled an additional 400 million miles – about four times the Earth’s average distance from the sun, to reach the accretion disk.

“This tells us that the mysterious X-ray source in the AGN hovers at some height above the accretion disk,” Chris Reynolds, a professor of astronomy at the ̽��ֱ�� of Maryland at College Park and a co-author on the study, said. Jets of accelerated particles are often found around AGNs, and the finding appears to endorse an idea which has already been postulated that whatever the X-ray source is, it may be located near to the bases of these jets.

“ ̽��ֱ��data show that the earliest echo comes from the most broadened iron line emission,” Andy Fabian, from the Institute of Astronomy at the ̽��ֱ�� of Cambridge, and another co-author, added. “This line originates from closest to the black hole, and fits well with what we were expecting.”

̽��ֱ��detection of X-ray echoes in the AGN opens up a new way of studying black holes and the disks of matter that accrete around them. Astronomers anticipate that the next generation of X-ray telescopes will have collecting areas large enough to detect the echo produced by a single flare from the X-ray source, giving them an even better tool for testing relativity and probing the immediate surroundings of massive black holes.

“Our analysis allows us to probe black holes through a different window,” Abderahmen Zoghbi, a postdoctoral research associate at the ̽��ֱ�� of Maryland at College Park and the report’s lead author, said. “It confirms some long-held ideas about AGN and gives us a sense of what we can expect when a new generation of space-based X-ray telescopes eventually becomes available.”

A long-sought “echo” of light that promises to reveal more about supersized black holes in distant galaxies has been identified by an international team of astronomers.

Our analysis allows us to probe black holes through a different window.

Abderahmen Zoghbi

NASA.

̽��ֱ��galaxy NGC 4151. Researchers were able to use this galaxy to accumulate data about flares coming from a mysterious X-ray source close to the giant black hole at its centre.

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