black holes Archivi - Scientificult

Astronomy

Massive black hole in the early universe is lying dormant in its host galaxy, GN-1001830

By ScientifiCult 18 December 2024

Massive black hole in the early universe spotted taking a ‘nap’ after overeating, and lying dormant in its host galaxy, GN-1001830

JWST buco nero dormiente GN-1001830 Illustrazione artistica che rappresenta l'aspetto potenziale del buco nero supermassiccio scoperto dal team di ricerca durante la sua fase di intensa attività super-Eddington. Crediti: Jiarong Gu — A study in *Nature* finds that black holes in the early Universe go through short periods of ultra-fast growth, followed by long periods of dormancy. Picture credits: Jiarong Gu

Scientists have spotted a massive black hole in the early universe that is ‘napping’ after stuffing itself with too much food.

Like a bear gorging itself on salmon before hibernating for the winter, or a much-needed nap after Christmas dinner, this black hole has overeaten to the point that it is lying dormant in its host galaxy, GN-1001830.

An international team of astronomers, led by the University of Cambridge, used the NASA/ESA/CSA James Webb Space Telescope to detect this black hole in the early universe, just 800 million years after the Big Bang.

The black hole is huge – 400 million times the mass of our Sun – making it one of the most massive black holes discovered by Webb at this point in the universe’s development. The black hole is so enormous that it makes up roughly 40% of the total mass of its host galaxy: in comparison, most black holes in the local universe are roughly 0.1% of their host galaxy mass.

However, despite its gigantic size, this black hole is eating, or accreting, the gas it needs to grow at a very low rate – about 100 times below its theoretical maximum limit – making it essentially dormant.

Such an over-massive black hole so early in the universe, but one that isn’t growing, challenges existing models of how black holes develop. However, the researchers say that the most likely scenario is that black holes go through short periods of ultra-fast growth, followed by long periods of dormancy. Their results are reported in the journal Nature.

When black holes are ‘napping’, they are far less luminous, making them more difficult to spot, even with highly-sensitive telescopes such as Webb. Black holes cannot be directly observed, but instead they are detected by the tell-tale glow of a swirling accretion disc, which forms near the black hole’s edges. The gas in the accretion disc becomes extremely hot and starts to glow and radiate energy in the ultraviolet range.

“Even though this black hole is dormant, its enormous size made it possible for us to detect,” said lead author Ignas Juodžbalis from Cambridge’s Kavli Institute for Cosmology. “Its dormant state allowed us to learn about the mass of the host galaxy as well. The early universe managed to produce some absolute monsters, even in relatively tiny galaxies.”

According to standard models, black holes form from the collapsed remnants of dead stars and accrete matter up to a predicted limit, known as the Eddington limit, where the pressure of radiation on matter overcomes the gravitational pull of the black hole. However, the sheer size of this black hole suggests that standard models may not adequately explain how these monsters form and grow.

“It’s possible that black holes are ‘born big’, which could explain why Webb has spotted huge black holes in the early universe,” said co-author Professor Roberto Maiolino, from the Kavli Institute and Cambridge’s Cavendish Laboratory. “But another possibility is they go through periods of hyperactivity, followed by long periods of dormancy.”

Working with colleagues from Italy, the Cambridge researchers conducted a range of computer simulations to model how this dormant black hole could have grown to such a massive size so early in the universe. They found that the most likely scenario is that black holes can exceed the Eddington limit for short periods, during which they grow very rapidly, followed by long periods of inactivity: the researchers say that black holes such as this one likely eat for five to ten million years, and sleep for about 100 million years.

“It sounds counterintuitive to explain a dormant black hole with periods of hyperactivity, but these short bursts allow it to grow quickly while spending most of its time napping,” said Maiolino.

Because the periods of dormancy are much longer than the periods of ultra-fast growth, it is in these periods that astronomers are most likely to detect black holes.

“This was the first result I had as part of my PhD, and it took me a little while to appreciate just how remarkable it was,” said Juodžbalis. “It wasn’t until I started speaking with my colleagues on the theoretical side of astronomy that I was able to see the true significance of this black hole.”

Due to their low luminosities, dormant black holes are more challenging for astronomers to detect, but the researchers say this black hole is almost certainly the tip of a much larger iceberg, if black holes in the early universe spend most of their time in a dormant state.

“It’s likely that the vast majority of black holes out there are in this dormant state – I’m surprised we found this one, but I’m excited to think that there are so many more we could find,” said Maiolino.

The observations were obtained as part of the JWST Advanced Deep Extragalactic Survey (JADES). The research was supported in part by the European Research Council and the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

Bibliographic Information:

“A dormant, overmassive black hole in the early Universe”, by Ignas Juodžbalis, Roberto Maiolino, William M. Baker, Sandro Tacchella, Jan Scholtz, Francesco D’Eugenio, Raffaella Schneider, Alessandro Trinca, Rosa Valiante, Christa DeCoursey, Mirko Curti, Stefano Carniani, Jacopo Chevallard, Anna de Graaff, Santiago Arribas, Jake S. Bennett, Martin A. Bourne, Andrew J. Bunker, Stephane Charlot, Brian Jiang, Sophie Koudmani, Michele Perna, Brant Robertson, Debora Sijacki, Hannah Ubler, Christina C. Williams, Chris Willott, Joris Witstok, has been published on Nature (18-Dec-2024).

Press release from the University of Cambridge

Keep Reading

Astronomy

The Sombrero Galaxy, or Messier 104, dazzles in new mid-infrared image from Webb

By ScientifiCult 25 November 2024

The Sombrero Galaxy, also known as Messier 104 (M104), dazzles in new mid-infrared image from Webb

A new mid-infrared image from the NASA/ESA/CSA James Webb Space Telescope features the Sombrero galaxy, also known as Messier 104 (M104). The signature, glowing core seen in visible-light images does not shine, and instead a smooth inner disk is revealed. The sharp resolution of Webb’s MIRI (Mid-Infrared Instrument) also brings into focus details of the galaxy’s outer ring, providing insights into how the dust, an essential building block for astronomical objects in the Universe, is distributed. The galaxy’s outer ring shows intricate clumps in the infrared for the first time.

Image of a galaxy on the black background of space. The galaxy is a very oblong, blue disk that extends from left to right at an angle (from about 10 o’clock to 5 o’clock). The galaxy has a small bright core at the centre. There is an inner disk that is clearer, with speckles of stars scattered throughout. The outer disk of the galaxy is whiteish-blue, and clumpy, like clouds in the sky. There are different coloured dots, distant galaxies, speckled among the black background of space surrounding the galaxy. — The NASA/ESA/CSA James Webb Space Telescope recently imaged the Sombrero galaxy with its MIRI (Mid-Infrared Instrument), resolving the clumpy nature of the dust along the galaxy’s outer ring.
The mid-infrared light highlights the gas and dust that are part of star formation taking place among the Sombrero galaxy’s outer disk. The rings of the Sombrero galaxy produce less than one solar mass of stars per year, in comparison to the Milky Way’s roughly two solar masses a year. It’s not a particular hotbed of star formation.
The Sombrero galaxy is around 30 million light-years from Earth in the constellation Virgo.
Credit: NASA, ESA, CSA, STScI

Researchers say the clumpy nature of the dust, where MIRI detects carbon-containing molecules called polycyclic aromatic hydrocarbons, can indicate the presence of young star-forming regions. However, unlike some galaxies studied with Webb, including Messier 82, where 10 times as many stars are born as in the Milky Way galaxy, the Sombrero galaxy is not a particular hotbed of star formation. The rings of the Sombrero galaxy produce less than one solar mass of stars per year, in comparison to the Milky Way’s roughly two solar masses a year.

The supermassive black hole at the centre of the Sombrero galaxy, also known as an active galactic nucleus (AGN), is rather docile, even at a hefty 9-billion-solar masses. It’s classified as a low luminosity AGN, slowly snacking on infalling material from the galaxy, while sending off a bright, relatively small, jet.

Also within the Sombrero galaxy dwell some 2000 globular clusters, a collection of hundreds of thousands of old stars held together by gravity. This type of system serves as a pseudo laboratory for astronomers to study stars – thousands of stars within one system with the same age, but varying masses and other properties is an intriguing opportunity for comparison studies.

In the MIRI image, galaxies of varying shapes and colours litter the background of space. The different colours of these background galaxies can tell astronomers about their properties, including how far away they are.

The Sombrero galaxy is around 30 million light-years from Earth in the constellation Virgo.

Stunning images like this, and an array of discoveries in the study of exoplanets, galaxies through time, star formation, and our own Solar System, are still just the beginning. Recently, scientists from all over the world converged—virtually—to apply for observation time with Webb during its fourth year of science operations, which begins in July 2025.

A two panel image. The top image is Webb’s view of the Sombrero galaxy, the bottom image is Hubble’s view. In the Webb view, the galaxy is a very oblong, blue disk that extends from left to right at an angle (from about 10 o’clock to 5 o’clock). The galaxy has a small bright core at the centre. There is a clear inner disk that has speckles of stars scattered throughout. The outer disk of the galaxy is whiteish-blue, and clumpy, like clouds in the sky. In the Hubble view, the galaxy is an oblong, pale white disk with a glowing core over the inner disk. The outer disk is darker and clumpy. — This image compares the view of the famous Sombrero Galaxy in mid-infrared light (top) and visible light (bottom). The James Webb Space Telescope’s MIRI (Mid-Infrared Instrument) reveals the smooth inner disk of the galaxy, while the Hubble Space Telescope’s visible light image shows the large and extended glow of the central bulge of stars.
Both the Webb and Hubble images resolve the clumpy nature of the dust that makes up the Sombrero galaxy’s outer ring.
Credit: NASA, ESA, CSA, STScI, Hubble Heritage Team (STScI/AURA)

General Observer time with Webb is more competitive than ever. A record-breaking 2377 proposals were submitted by the 15 October 2024 deadline, requesting about 78,000 hours of observation time. This is an oversubscription rate, the ratio defining the observation hours requested versus the actual time available in one year of Webb’s operations, of around 9 to 1.

The proposals cover a wide array of science topics, with distant galaxies being among the most requested observation time, followed by exoplanet atmospheres, stars and stellar population, then exoplanet systems.

Press release from ESA Webb

Keep Reading

Astronomy

Hubble finds more black holes than expected in the early Universe

By ScientifiCult 17 September 2024

Hubble finds more black holes than expected in the early Universe

With the help of the NASA/ESA Hubble Space Telescope, an international team of researchers led by scientists in the Department of Astronomy at Stockholm University has found more black holes in the early Universe than has previously been reported. The new result can help scientists understand how supermassive black holes were created.

This is a Hubble image of a black sky sprinkled with myriad galaxies of all shapes and sizes stretching back to nearly the beginning of the Universe. In the middle of the picture there is an inset box showing one sample pair of early galaxies. One galaxy is spiral-shaped and the other is spindle-shaped because it is a disc galaxy seen edge-on. The spindle-shaped galaxy has an active supermassive black hole that appears as a bright white spot. This is identified by comparing pictures of the same region taken at different epochs. — This is a new image of the Hubble Ultra Deep Field. The first deep imaging of the field was done with Hubble in 2004. The same survey field was observed again by Hubble several years later, and was then reimaged in 2023. By comparing Hubble Wide Field Camera 3 near-infrared exposures taken in 2009, 2012, and 2023, astronomers found evidence for flickering supermassive black holes in the hearts of early galaxies. One example is seen as a bright object in the inset. Some supermassive black holes do not swallow surrounding material constantly, but in fits and bursts, making their brightness flicker. This can be detected by comparing Hubble Ultra Deep Field frames taken at different epochs. The survey found more black holes than predicted.
The image was created from Hubble data from the following proposals: 9978, 10086 (S. Beckwith); 11563 (G. Illingworth); 12498 (R. Ellis); and 17073 (M. Hayes). These images are composites of separate exposures acquired by the ACS and WFC3 instruments on the Hubble Space Telescope.
Credit: NASA, ESA, M. Hayes (Stockholm University), J. DePasquale (STScI)

Scientists do not currently have a complete picture of how the first black holes formed, not long after the Big Bang. It is known that supermassive black holes, that can weigh more than a billion suns, exist at the centre of several galaxies less than a billion years after the Big Bang.

“Many of these objects seem to be more massive than we originally thought they could be at such early times — either they formed very massive or they grew extremely quickly,” said Alice Young, a PhD student from Stockholm University and co-author of the study published in The Astrophysical Journal Letters.

Black holes play an important role in the lifecycle of all galaxies, but there are major uncertainties in our understanding of how galaxies evolve. In order to gain a complete picture of the link between galaxy and black hole evolution, the researchers used Hubble to survey how many black holes exist among a population of faint galaxies when the Universe was just a few percent of its current age.

Initial observations of the survey region were re-photographed by Hubble several years later. This allowed the team to measure variations in the brightness of the galaxies. These variations are a tell-tale sign of black holes. The team identified more black holes than previously found by other methods.

The new observational results suggest that some black holes likely formed by the collapse of massive, pristine stars during the first billion years of cosmic time. These types of stars can only exist at very early times in the Universe, because later generations of stars are polluted by the remnants of stars that have already lived and died. Other alternatives for black hole formation include collapsing gas clouds, mergers of stars in massive clusters, and ‘primordial’ black holes that formed (by physically speculative mechanisms) in the first few seconds after the Big Bang. With this new information about black hole formation, more accurate models of galaxy formation can be constructed.

“The formation mechanism of early black holes is an important part of the puzzle of galaxy evolution,” said Matthew Hayes from the Department of Astronomy at Stockholm University and lead author of the study. “Together with models for how black holes grow, galaxy evolution calculations can now be placed on a more physically motivated footing, with an accurate scheme for how black holes came into existence from collapsing massive stars.”

Astronomers are also making observations with the NASA/ESA/CSA James Webb Space Telescope to search for galactic black holes that formed soon after the Big Bang, to understand how massive they were and where they were located.

Press release from ESA Webb.

Keep Reading

Astronomy

Webb detects most distant black hole merger to date in the ZS7 galaxy system

By ScientifiCult 16 May 2024

Webb detects most distant black hole merger to date in the ZS7 galaxy system

An international team of astronomers have used the NASA/ESA/CSA James Webb Space Telescope to find evidence for an ongoing merger of two galaxies and their massive black holes when the Universe was only 740 million years old. This marks the most distant detection of a black hole merger ever obtained and the first time that this phenomenon has been detected so early in the Universe.

Three panels are shown showing an increasingly small area of the PRIMER galaxy field. The first image shows a large field of galaxies on the black background of space. The second image shows a smaller region from this field, revealing the galaxies in closer detail, appearing in a variety of shapes and colours. The final image shows the ZS7 galaxy system, revealing the ionised hydrogen emission in orange and the doubly ionised oxygen emission in dark red. — This image shows the location of the galaxy system ZS7 from the JWST PRIMER programme (PI: J. Dunlop). New research using the NIRSpec instrument on the NASA/ESA/CSA James Webb Space Telescope have determined the system to be evidence of an ongoing merger of two galaxies and their massive black holes when the Universe was only 740 million years old. This marks the most distant detection of a black hole merger ever obtained and the first time that this phenomenon has been detected so early in the Universe.
The team has found evidence for very dense gas with fast motions in the vicinity of the black hole, as well as hot and highly ionised gas illuminated by the energetic radiation typically produced by black holes in their accretion episodes. Webb also allowed the team to spatially separate the two black holes and determined that one of the two black holes has a mass that is 50 million times the mass of the Sun. The mass of the other black hole is likely similar, although it is harder to measure because this second black hole is buried in dense gas.
In this Webb NIRCam image, the ionised hydrogen (Hβ) emission in the ZS7 system is identified by the orange region and the doubly ionised oxygen (OIII) emission is visible in dark red (right image).
Credit: ESA/Webb, NASA, CSA, J. Dunlop, D. Magee, P. G. Pérez-González, H. Übler, R. Maiolino, et al.

Astronomers have found supermassive black holes with masses of millions to billions times that of the Sun in most massive galaxies in the local Universe, including in our Milky Way galaxy. These black holes have likely had a major impact on the evolution of the galaxies they reside in. However, scientists still don’t fully understand how these objects grew to become so massive. The finding of gargantuan black holes already in place in the first billion years after the Big Bang indicates that such growth must have happened very rapidly, and very early. Now, the James Webb Space Telescope is shedding new light on the growth of black holes in the early Universe.

The new Webb observations have provided evidence for an ongoing merger of two galaxies and their massive black holes when the Universe was just 740 million years old. The system is known as ZS7.

Massive black holes that are actively accreting matter have distinctive spectrographic features that allow astronomers to identify them. For very distant galaxies, like those in this study, these signatures are inaccessible from the ground and can only be seen with Webb.

“We found evidence for very dense gas with fast motions in the vicinity of the black hole, as well as hot and highly ionised gas illuminated by the energetic radiation typically produced by black holes in their accretion episodes,” explained lead author Hannah Übler of the University of Cambridge in the United Kingdom. “Thanks to the unprecedented sharpness of its imaging capabilities, Webb also allowed our team to spatially separate the two black holes.”

The team found that one of the two black holes has a mass that is 50 million times the mass of the Sun.

“The mass of the other black hole is likely similar, although it is much harder to measure because this second black hole is buried in dense gas,”

explained team member Roberto Maiolino of the University of Cambridge and University College London in the United Kingdom.

“Our findings suggest that merging is an important route through which black holes can rapidly grow, even at cosmic dawn,” explained Übler. “Together with other Webb findings of active, massive black holes in the distant Universe, our results also show that massive black holes have been shaping the evolution of galaxies from the very beginning.”

“The stellar mass of the system we studied is similar to that of our neighbor the Large Magellanic Cloud,” shared team member Pablo G. Pérez-González of the Centro de Astrobiología (CAB), CSIC/INTA, in Spain. “We can try to imagine how the evolution of merging galaxies could be affected if each galaxy had one super massive black hole as large or larger than the one we have in the Milky Way”.

This image features the ZS7 galaxy system, showing a large field of hundreds of galaxies on the black background of space. — This image shows the environment of the galaxy system ZS7 from the JWST PRIMER programme (PI: J. Dunlop) as seen by Webb’s NIRCam instrument.
New research using the NIRSpec instrument on the NASA/ESA/CSA James Webb Space Telescope has determined the system to be evidence of an ongoing merger of two galaxies and their massive black holes when the Universe was only 740 million years old. This marks the most distant detection of a black hole merger ever obtained and the first time that this phenomenon has been detected so early in the Universe.
The team has found evidence for very dense gas with fast motions in the vicinity of the black hole, as well as hot and highly ionised gas illuminated by the energetic radiation typically produced by black holes in their accretion episodes. Webb also allowed the team to spatially separate the two black holes and determined that one of the two black holes has a mass that is 50 million times the mass of the Sun. The mass of the other black hole is likely similar, although it is harder to measure because this second black hole is buried in dense gas.
Credit: ESA/Webb, NASA, CSA, J. Dunlop, D. Magee, P. G. Pérez-González, H. Übler, R. Maiolino, et al.

The team also notes that once the two black holes merge, they will also generate gravitational waves [1]. Events like this will be detectable with the next generation of gravitational wave observatories, such as the upcoming Laser Interferometer Space Antenna (LISA) mission, which was recently approved by the European Space Agency and will be the first space-based observatory dedicated to studying gravitational waves.

“Webb’s results are telling us that lighter systems detectable by LISA should be far more frequent than previously assumed,” shared LISA Lead Project Scientist Nora Luetzgendorf of the European Space Agency in the Netherlands. “It will most likely make us adjust our models for LISA rates in this mass range. This is just the tip of the iceberg.”

This discovery was from observations made as part of the Galaxy Assembly with NIRSpec Integral Field Spectroscopy programme. The team has recently been awarded a new Large Programme in Webb’s Cycle 3 of observations, to study in detail the relationship between massive black holes and their host galaxies in the first billion years. An important component of this programme will be to systematically search for and characterise black hole mergers. This effort will determine the rate at which black hole merging occurs at early cosmic epochs and will assess the role of merging in the early growth of black holes and the rate at which gravitational waves are produced from the dawn of time.

These results have been published in the Monthly Notices of the Royal Astronomical Society.

Notes

[1] Gravitational waves are invisible ripples in the fabric of spacetime. Spacetime is a four-dimensional quantity, described by Einstein’s general theory of relativity, which fuses three-dimensional space with time. Mass warps spacetime, and gravity is actually the result of spacetime being curved by an object’s mass. Ripples through spacetime are created by the movement of any object with mass, and these are known as gravitational waves. Gravitational waves are constantly passing unnoticed through Earth and they are caused by some of the most violent and energetic events in the Universe. These include colliding black holes, collapsing stellar cores, merging neutron stars or white dwarf stars, the wobble of neutron stars that are not perfect spheres and possibly even the remnants of gravitational radiation created at the birth of the Universe.

Press release from ESA Webb.

Keep Reading

Astronomy

Hubble hunts for intermediate-sized black hole close to home

By ScientifiCult 23 May 2023

Hubble hunts for intermediate-sized black hole close to home; the study has been published in the Monthly Notices of the Royal Astronomical Society

Astronomers using the NASA/ESA Hubble Space Telescope have come up with what they say is some of their best evidence yet for the presence of a rare class of intermediate-sized black holes, having found a strong candidate lurking at the heart of the closest globular star cluster to Earth, located 6000 light-years away.

Messier 4 M4 — Hubble hunts for intermediate-sized black hole close to home. A Hubble Space Telescope image of the globular star cluster, Messier 4. The cluster is a dense collection of several hundred thousand stars. Astronomers suspect that an intermediate-mass black hole, weighing as much as 800 times the mass of our Sun, is lurking, unseen, at its core. Credit: ESA/Hubble & NASA

Like intense gravitational potholes in the fabric of space, virtually all black holes seem to come in two sizes: small and humongous. It’s estimated that our galaxy is littered with 100 million small black holes (several times the mass of our Sun) created from exploded stars. The universe at large is flooded with supermassive black holes, weighing millions or billions of times our Sun’s mass and found in the centres of galaxies.

A long-sought missing link is an intermediate-mass black hole, weighing roughly 100 to 100,000 times our Sun’s mass. How would they form, where would they hang out, and why do they seem to be so rare?

Astronomers have identified other possible intermediate-mass black holes using a variety of observational techniques. Two of the best candidates — 3XMM J215022.4-055108, which Hubble helped discover in 2020, and HLX-1, identified in 2009 — reside in the outskirts of other galaxies. Each of these possible black holes has the mass of tens of thousands of suns, and may have once been at the centres of dwarf galaxies.

Looking much closer to home, there have been a number of suspected intermediate-mass black holes detected in dense globular star clusters orbiting our Milky Way galaxy. For example, in 2008, Hubble astronomers announced the suspected presence of an intermediate-mass black hole in the globular cluster Omega Centauri. For a number of reasons, including the need for more data, these and other intermediate-mass black hole findings still remain inconclusive and do not rule out alternative theories.

Hubble’s unique capabilities have now been used to zero-in on the core of the globular star cluster Messier 4 (M4) to go black-hole hunting with higher precision than in previous searches.

“You can’t do this kind of science without Hubble,”

said Eduardo Vitral of the Space Telescope Science Institute in Baltimore, Maryland, and formerly of the Institut d’Astrophysique de Paris (IAP, Sorbonne University) in Paris, France, lead author on a paper to be published in the Monthly Notices of the Royal Astronomical Society.

Vitral’s team has detected a possible intermediate-mass black hole of roughly 800 solar masses. The suspected object can’t be seen, but its mass is calculated by studying the motion of stars caught in its gravitational field, like bees swarming around a hive. Measuring their motion takes time, and a lot of precision. This is where Hubble accomplishes what no other present-day telescope can do. Astronomers looked at 12 years’ worth of M4 observations from Hubble, and resolved pinpoint stars.

ESA’s Gaia spacecraft also contributed to this result with scans of over 6000 stars that constrained the global shape of the cluster and its mass. Hubble’s data tend to rule out alternative theories for this object, such as a compact central cluster of unresolved stellar remnants like neutron stars, or smaller black holes swirling around each other.

“Using the latest Gaia and Hubble data, it was not possible to distinguish between a dark population of stellar remnants and a single larger point-like source,” says Vitral. “So one of the possible theories is that rather than being lots of separate small dark objects, this dark mass could be one medium-sized black hole.”

“We have good confidence that we have a very tiny region with a lot of concentrated mass. It’s about three times smaller than the densest dark mass that we had found before in other globular clusters,” he continued. “The region is more compact than what we can reproduce with numerical simulations when we take into account a collection of black holes, neutron stars, and white dwarfs segregated at the cluster’s centre. They are not able to form such a compact concentration of mass.”

A grouping of close-knit objects would be dynamically unstable. If the object isn’t a single intermediate-mass black hole, it would require an estimated 40 smaller black holes crammed into a space only one-tenth of a light-year across to produce the observed stellar motions. The consequences are that they would merge and/or be ejected in a game of interstellar pinball.

“We measure the motions of stars and their positions, and we apply physical models that try to reproduce these motions. We end up with a measurement of a dark mass extension in the cluster’s centre,” said Vitral. “The closer to the central mass, the more randomly the stars are moving. And, the greater the central mass, the faster these stellar velocities.”

Because intermediate-mass black holes in globular clusters have been so elusive, Vitral cautions, “While we cannot completely affirm that it is a central point of gravity, we can show that it is very small. It’s too tiny for us to be able to explain other than it being a single black hole. Alternatively, there might be a stellar mechanism we simply don’t know about, at least within current physics.”

“Science is rarely about discovering something new in a single moment. It’s about becoming more certain of a conclusion step by step, and this could be one step towards being sure that intermediate-mass black holes exist,” explains Gaia mission scientist Timo Prusti. “Data from Gaia Data Release 3 on the proper motion of stars in the Milky Way were essential in this study. Future Gaia Data Releases, as well as follow-up studies from the Hubble and James Webb Space Telescopes could shed further light.”

Press release from ESA Hubble

Keep Reading

Astronomy

Black holes? They are like a hologram

By ScientifiCult 5 June 2020

According to new research, black holes could be like a hologram, where all the information is amassed in a two-dimensional surface able to reproduce a three-dimensional image. The study which demonstrates it, and which unites two discordant theories, has recently been published in Physical Review X

black holes hologram — What researchers have done is apply the theory of the holographic principle to black holes. In this way, their mysterious thermodynamic properties have become more understandable: focusing on predicting that these bodies have a great entropy and observing them in terms of quantum mechanics, you can describe them just like a hologram: they have two dimensions, in which gravity disappears, but they reproduce an object in three dimensions. Credits: Gerd Altmann for Pixabay

We can all picture that incredible image of a black hole that travelled around the world about a year ago. Yet, according to new research by SISSA, ICTP and INFN, black holes could be like a hologram, where all the information is amassed in a two-dimensional surface able to reproduce a three-dimensional image. In this way, these cosmic bodies, as affirmed by quantum theories, could be incredibly complex and concentrate an enormous amount of information inside themselves, as the largest hard disk that exists in nature, in two dimensions.

This idea aligns with Einstein’s theory of relativity, which describes black holes as three dimensional, simple, spherical, and smooth, as they appear in that famous image. In short, black holes “appear” as three dimensional, just like holograms. The study which demonstrates it, and which unites two discordant theories, has recently been published in .

The mystery of black holes

For scientists, black holes are a big question mark for many reasons. They are, for example, excellent representatives of the great difficulties of theoretical physics in putting together the principles of Einstein’s general theory of relativity with those of quantum physics when it comes to gravity. According to the first theory, they would be simple bodies without information. According to the other, as claimed by Jacob Bekenstein and Stephen Hawking, they would be “the most complex existing systems” because they would be characterised by an enormous “entropy”, which measures the complexity of a system, and consequently would have a lot of information inside them.

The holographic principle applied to black holes

To study black holes, the two authors of the research, Francesco Benini (SISSA Professor, ICTP scientific consultant and INFN researcher) and Paolo Milan (SISSA and INFN researcher), used an idea almost 30 years old, but still surprising, called the “holographic principle”. The researchers say: “This revolutionary and somewhat counterintuitive principle proposes that the behavior of gravity in a given region of space can alternatively be described in terms of a different system, which lives only along the edge of that region and therefore in a one less dimension. And, more importantly, in this alternative description (called holographic) gravity does not appear explicitly. In other words, the holographic principle allows us to describe gravity using a language that does not contain gravity, thus avoiding friction with quantum mechanics”.

What Benini and Milan have done “is apply the theory of the holographic principle to black holes. In this way, their mysterious thermodynamic properties have become more understandable: focusing on predicting that these bodies have a great entropy and observing them in terms of quantum mechanics, you can describe them just like a hologram: they have two dimensions, in which gravity disappears, but they reproduce an object in three dimensions”.

From theory to observation

“This study,” explain the two scientists, “is only the first step towards a deeper understanding of these cosmic bodies and of the properties that characterise them when quantum mechanics crosses with general relativity. Everything is more important now at a time when observations in astrophysics are experiencing an incredible development. Just think of the observation of gravitational waves from the fusion of black holes result of the collaboration between LIGO and Virgo or, indeed, that of the black hole made by the Event Horizon Telescope that produced this extraordinary image. In the near future, we may be able to test our theoretical predictions regarding quantum gravity, such as those made in this study, by observation. And this, from a scientific point of view, would be something absolutely exceptional”.

Press release from the Scuola Internazionale Superiore di Studi Avanzati

Keep Reading