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Quantum computing and quantum computers

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What is quantum computing? Why do we need quantum computing? According to Moore’s law (“The complexity of a microcircuit, measured for example by the number of transistors per chip, doubles every 18 months and hence quadruples every 3 years”), the density of transistors per area unit on a computing chip doubles every year and a half, which poses two main problems for traditional computers. Firstly, as to computation, high-density transistors will face the problem of power consumption and thermal effects. Secondly, the reduction in size will cause the failure of the classic theory of transistors and their performance will deviate from the original design.

Both of these problems will limit the further shrinkage of transistors, thus putting an end to Moore’s law. However, although the traditional computer develops until the end of Moore’s law, it is still unable to cope with many problems that need to be solved. Let us say we calculate the fundamental state energy of N coupled two-level systems, since the number of unknowns will be proportional to 2^N. The current simulation time required for IBM’s supercomputer is 2.5 days for a specific computation on Google’s 53-qubit quantum computer, which takes about 200 seconds. Qubit is the contraction of quantum bit, the term coined by Benjamin Schumacher to denote the quantum bit, i.e. the basic unit of quantum information.

As the number of qubits continues to increase, conventional computers will soon reach a bottleneck. However, almost all conventional computations involving quantum mechanics face the same problems. Hence many researchers started thinking about how to use the quantum properties themselves as computational resources as early as 1970, which was then summarised by Richard Feynman in 1982.

Hence what advantages do qubits have over traditional computing? The most surprising is none other than the properties of quantum superposition and quantum entanglement. Quantum superposition is a non-classical state that contrasts with empirical intuition and the metaphor is Schrödinger’s Cat that is both alive and dead.

The superposition state, however, is a real state for qubits on microscopic or mesoscopic scales (spatial scales, viewpoints and the like that are intermediate between macroscopic and microscopic scales). Qubits can be found in the superposition of two characteristic quantum states, and this superposition state is a non-classical state in which being and non-being coexist in the quantum world. In this state, the qubit is neither 0 nor 1, but it is not in a state in which both sides (0 and 1) are uncertain, but rather with equal probability, like a coin before it lands on the palm of the hand.

While in visible nature it is possible to observe a phenomenon without perceptibly influencing it by observation alone (i.e. only by looking at the said phenomenon) – in atomic physics and quantum mechanics, a finite – and up to a certain point – invisible perturbation is connected to every observation. The uncertainty principle is the recognition of absolute chance and arbitrariness in natural phenomena. On the other hand, as will become clear later, quantum mechanics does not predict a single, well-defined result for the observation or for any observer.

The fact that qubits can undergo quantum evolution in a set of superposition states – which is neither 0 nor 1 – implies quantum parallelism in the relevant computation. The evolution of each qubit, however, is not sufficient to construct all possible evolutions of a multi-qubit system. We must therefore

also interact with different qubits so that they can be intertwined in order to construct a satisfactory algorithm for such a computation. This special superposition is precisely called entangled quantum state.

Let us take two qubits as an example, which is a typical entangled state. Between them, the state representing the first qubit is connected to the state of the second qubit. The two connections are in quantum superposition and we cannot therefore talk about the state in which the two qubits are at that moment – hence we talk about entanglement.

There is a more practical view of entanglement in quantum computing, i.e. entangled states usually arise from the control of one qubit (control qubit) over another (target qubit). The relationship between the control qubit and the target qubit is similar to the aforementioned Schrödinger’s Cat. According to this view, if the controlling part is in a state of superposition, the controlled part will be in a superposition of different controlled situations.

This entanglement process is an important element in quantum computing. We can say that superposition and entanglement synergistically weave the varied parallel evolution of quantum computing. Each measurement can only compute one of the possible states, and the superposition state no longer exists after the first measurement. Hence, with a view to obtaining the statistical information we need in the superposition state, we have to compute and measure results again.

Therefore, in many quantum algorithms (such as the Shor’s algorithm for factoring [which solves the problem of factor decomposition of integer numbers into primes] and digital quantum simulation), we need to use some interference mechanisms after the computation, so that the information of that phase containing the response in the superposition state is converted into conservation (with the implicit idea of preventing a final spill or loss) due to constructive interference (i.e. by the immediately following variation of other data produced), while further data is eliminated by destructive interference. In this way, the response can be obtained with fewer measurements. Most quantum algorithms rely heavily on the phenomenon of fluctuation and interference – hence the relative phase is very important for quantum computing, which is called quantum coherence. In the hardware design of quantum computers, many considerations are related to how to protect the quantum state to prolong the coherence lifetime.

Quantum computers have a variety of hardware implementations, but the design considerations are similar. There are three common considerations: qubit operability, measurability, and protection of quantum states. In response to these considerations, a cavity quantum electrodynamics (cQED) system has been developed. A superconducting quantum system can be taken as an example to introduce the implementation of quantum computers. The difference in frequency between the resonant cavity and the qubit means that the coupling between the resonant cavity and the qubit tends not to exchange energy quanta, but only to generate entanglement, which means that the frequency of the resonant cavity will shift with the state of the qubit. Hence the state of the qubit can be deduced by measuring the microwave penetration or reflection spectrum near the resonant frequency with the bit readout line.

The entanglement mechanism between adjacent qubits is provided by the coupling relative to the electrical capacitance between cross-type capacitors. The coupling effect is controlled by the frequency difference between adjacent qubits. The oscillating behaviour reflects the quantum interference effect and its gradual disappearance leads to the decay of coherence and quantum energy.

The coherent lifetime of qubits is influenced by two factors, an intrinsic and an extrinsic one. The extrinsic influence comes mainly from the coupling between the qubit and the quantum state readout circuit. The presence of a filter-like protection mechanism in the microwave cavity between the bit and the readout line can provide a qubit-like protection mechanism because the cavity and the qubit have a frequency difference of about 718 MHz. The intrinsic influence comes mainly from the loss of the qubit itself and the sensitivity of its frequency to various types of noise, which can usually be suppressed by improved materials and processes and optimisation of the geometric structure.

Quantum computing has a wide range of applications, currently involved in the fields of decryption and cryptography, quantum chemistry, quantum physics, optimisation problems and artificial intelligence. This covers almost all aspects of human society and will have a significant impact on human life after practice. However, the best quantum computers are not yet able to express the advantages of quantum computing. Although the number of qubits on a quantum computer has exceeded 50, the circuit depth required to run the algorithm is far from sufficient. The main reason is that the error rate of qubits in the computation process is still very high, even though we can use quantum correction of qubits and fault-tolerant quantum computation. In the case of quantum computing, the accuracy which gradually improves data will greatly increase the difficulty of producing the hardware and the complexity of the algorithm. At present, the implementation of some well-known algorithms has only reached the level of conceptual demonstration, which is sufficient to demonstrate the feasibility of quantum computing, but practical application still has a long way to go.

But we should remain optimistic because, although general quantum computation still needs to be improved by quantum computer hardware, we can still find new algorithms and applications. Moreover, the development of hardware can also make great strides, just like the development of traditional computers in the beginning. In line with this goal, many existing technological industries could be upgraded in the near future. Research is running fast thanks also to significant public and private investment, and the first commercial applications will be seen in the short term.

Considering defence and intelligence issues, many governments are funding research in this area. The People’s Republic of China and the United States of America have launched multi-year plans worth billions of yuan and dollars. The European Union has also established the Quantum Flagship Programme for an investment of one billion euros.

Advisory Board Co-chair Honoris Causa Professor Giancarlo Elia Valori is an eminent Italian economist and businessman. He holds prestigious academic distinctions and national orders. Mr. Valori has lectured on international affairs and economics at the world’s leading universities such as Peking University, the Hebrew University of Jerusalem and the Yeshiva University in New York. He currently chairs “International World Group”, he is also the honorary president of Huawei Italy, economic adviser to the Chinese giant HNA Group. In 1992 he was appointed Officier de la Légion d’Honneur de la République Francaise, with this motivation: “A man who can see across borders to understand the world” and in 2002 he received the title “Honorable” of the Académie des Sciences de l’Institut de France. “

Science & Technology

Listening to the reason of voice

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Speech and language skills are unique to modern humans. While this ability evolved over millions of years, it is not possible to trace language in the fossil record because it leaves no direct imprint. Instead, re-examining the ways our nearest living relatives communicate is helping to unravel this mysterious capability.

The mystery is deepened by the fact that our closest living relatives, the great apes, do not talk. Some scientists now believe that the evolution of our language capabilities are more discernible in living primates than previously assumed. 

‘The traditional view is that, even though great apes are our closest living relatives, they are not useful for studying how language and speech came about, because their vocal behaviour is so different,’ said primatologist Dr Adriano Lameira at the University of Warwick, UK. ‘It’s automatic and reflexive, guided by blind instinct.’

During his years spent in jungles studying orangutans in the wild, Lameria discovered that the range and novelty of vocal sounds in wild orangutans varies, and he recently reported that this depends on local population density. Novelty is at a premium when an individual needs to stand out, so that apes living in areas of high population density express their individuality through more distinctive and variable vocal sounds. 

Tiger sheets

In Indonesia, Lameira experimented by crawling around the forest floor on all fours, disguised with a tiger-patterned sheet. Recording the responses of the forest apes, he discovered that orangutan mums holding an infant stay silent when they spot “a tiger,” which stayed within sight for two minutes. They suppress alert calls for up to 20 minutes after the tiger has gone.

From there, he reasoned that immediate vocalisation could endanger the young orangutan. ‘A Sumatran tiger can climb 10 metres up a tree in a second,’ said Lameira. ‘If you advertise your location, especially if you have an infant, it could be very dangerous.’ 

By vocalising after the tiger has moved on, the mother alerts the infant to the danger. This helps the juvenile to make the correct association. The remarkable thing about this is that the orangutan was communicating about a past event, rather than something in the here and now. ‘This was completely outside the box of what we had been thinking,’ said Lameira. 

It opens up the possibility that orangutans communicate about past events, or perhaps even future events. If this ability exists, the possibilities for sharing information are endless. ‘This could well be a trait that was shared by our last common ancestor – this capacity of communicating about events that are not in the here and now.’ 

It may be that other apes are also able to do this to some degree. ‘Even if you communicate only about 20 minutes in the past, or future, you can accrue benefits,’ said Lameira. ‘Natural selection just needs a little bit of something to tinker with and improve upon.’ Perhaps apes can communicate that a certain tree has such-and-such fruit, though this suggestion remains speculative. 

Monkey talk 

In the south of France, Dr Pascal Belin studies captive macaque and marmoset monkeys to investigate their perception of vocalisations. 

‘The goal of the research is to better understand the way the human brain evolved,’ said Belin, a neuroscientist at the Aix-Marseille University in France. ‘We study humans and three other types of primates – marmosets, macaques and baboons – to try to better understand differences and similarities, especially in vocal communications.’

In one experiment, three macaques were trained to stay still in an MRI machine, which scanned their brains as they listened to dozens of sounds, including vocalisations from other macaques.

‘Like in the human brain, the macaques and marmosets seem to have regions that are particularly sensitive to conspecific (from the same species) vocalisations,’ said Belin. The MRI scans show which areas become active as the macaques listen to other macaques, but not natural or other sounds or marmosets. A very similar area is active when humans listen to human voices. 

If the same area of the brain in macaques and humans lights up when they hear another member of their species, this points to this voice area having evolved before they diverged in the evolutionary tree.

Belin’s hypothesis is that the voice information processing part of the primate brain is quite similar and therefore evolved in a common ancestor, before ancient humans such as Homo erectus emerged in Africa 2-3 million years ago.

‘It would suggest that the last common ancestor of humans and macaques already had a precursor of this voice area in the brain 20 million years ago,’ said Belin. 

Future experiments are planned to use surgically implanted electrodes in the monkeys to try to distinguish exactly which neurons become active when the macaques hear another macaque, but not other monkeys or other sounds or noises.

It may even be possible to then compare results from marmosets and macaques to humans, fitted with these electrodes for medical reasons. These are implanted in some epileptic patients, who don’t respond to treatments, to allow neurosurgeons to better see small areas of the brain that they may need to remove. 

Such patients could be asked to listen to the same 96 sounds as the marmosets and macaques while being monitored in hospital, to study the brain’s response.

Consonant contacts

Yet it is not only the similarities that are interesting, but differences too. Great apes can make vowel-like sounds, as do monkeys, with their voice box. Yet only great apes and humans seem to make consonant-like sounds, which rely less on the vocal tract and more on the lips.

Orangutans have a rich repertoire of lip-smacking clicks and raspberries, which they combine with grunts and other vowel-like sounds. ‘They combine voiced calls with voiceless calls, so like vowel-like with consonant-like sounds,’ said Lameira. ‘We think there is something quite unique about this marriage between two distinct types of call, so powerful that every language was built on this formula of consonant plus vowel.’

This repertoire comprised critical starter blocks for our ancestors to begin developing what we today would recognise as human speech and language, Lameira suspects. Such shared traits, in Lameira’s view, is one way to trace back the path of human speech and language evolution and understand key steps forward that our ancestors took in terms of vocalisations and brain evolution. 

He calls on scientists studying gorillas, bonobos and chimpanzees to similarly look for shared traits, such as combinations of some consonant-like and vowel-like sounds, or evidence of communications about recent past events. By investigating our primate relatives, we may uncover vestiges of ancestral humans and the origins of our speech and language of today.

The research in this article was funded by the EU. This article was originally published in Horizon, the EU Research and Innovation Magazine.  

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Space exploration and the future exploitation of asteroids

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The discoveries of exoplanets in recent years have been absolutely extraordinary, and they could relatively soon be reached by our technology. At Cape Canaveral in Florida, on April 18, 2018 at 6:51pm, the Falcon Nine rocket was launched to send NASA’s Transiting Exoplanet Survey Satellite or TESS space telescope into orbit. It is a probe that scans the sky for planets about 100 light years away orbiting stars similar to our Sun.

Over the next decade, scientists expect TESS to fulfil its primary mission, which is to discover thousands of exoplanets. Exoplanets are planets that lie beyond the solar system. This is a golden age as far as discoveries are concerned. Only some 20 years ago we did not know that there were Earth-like planets in the Universe and it is hard to believe how many more things will come to light at such a pace. It is difficult to keep up with today’s discoveries: as of May 1 this year, there were 5,017 exoplanets.

Only recently, thanks to the development of satellites and high-power, high-definition telescopes, has it been possible to study neighbouring planets more accurately, particularly those capable of harbouring life. In the past, the idea that Earth-like planets could exist in the galaxy was not only inconceivable, but was also considered heretical blasphemy (Giordano Bruno’s execution was a case in point).

In the early 1990s astronomers, although with high-powered telescopes, were unable to detect distant planets. It is not easy to see an exoplanet: just imagine looking at a firefly next to a reflector. The process is extremely difficult because stars shine with their own light and planets reflect their light: generally speaking, a star is about 10 billion times brighter than a planet but, thanks to remarkable technological advances, two astronomers – Polish scientist Aleksander Wolszczan and Canadian scientist Dale Frail – detected two planets – Poltergeist and Phobetor – through a terrestrial telescope, near the newly discovered pulsar star B1257+12. The case of 51 Pegasi b (Bellerophon-Dimidium), which was spectroscopically detected by the Swiss Michel Mayor and Didier Queloz in 1995, is different. It orbits a Sun-like star (51 Pegasi) and is therefore considered to be the first exoplanet in all respects. On October 8, 2019, the two Swiss scientists received the Nobel Prize in Physics.

The search had already intensified ten years earlier, in 2009, with the launch of Kepler, the first space telescope designed to detect exoplanets. In 2018 Kepler was replaced by the aforementioned even more powerful TESS. The most interesting aspect of TESS is that it was designed for the specific purpose of detecting exoplanets using the transit method, which detects the decrease in brightness of a star’s light due to the transit of a planet. The decrease in brightness signals the transiting body and the orbit is determined, based on the frequency. It is an excellent method for finding new planets.

Although the search for exoplanets was initially aimed at establishing how many planets in the galaxy orbit the stars, the results are staggering: our galaxy has about 400 billion stars and, according to recent discoveries, on average each star hosts at least one planet: this means that there are at least 400 billion planets in our galaxy, the Milky Way.

The discovery of such a large number of exoplanets is a radical change in our knowledge of the Universe, but the idea that millions of planets might not only be able to host other life forms, but also to generate them, is even more extreme. To this end, astronomers and astrophysicists are searching for planets in a region they call the habitable zone. The habitable zone is the area around the star that enables the planet to maintain water in a liquid state. Scientists are looking for a planet in an optimal location, not too close or far from the parent star, that has enough oxygen and water to make the atmosphere, and probably even life, possible.

Scientists are astounded at the amount of planets discovered in the habitable zone that could harbour life forms: as mentioned above, there are at least 400 billion planets in our galaxy – hence even just one per cent equates to four billion planets that could potentially be habitable. The discovery of exoplanets has radically changed the way we think about the entire Universe: almost all scientists believe that other forms of life may exist. Despite the large number of habitable exoplanets, many scientists argue that only microbial or bacterial life forms could exist outside the Earth. They are wary of what they call far-fetched theories that planets could harbour more sophisticated and evolved intelligent life forms, probably equipped with more advanced technologies than ours. Japanese-born astrophysicist Michio Kaku – a summa cum laude graduate of Harvard University – said: ‘Think about it. The Universe is about 13.8 billion years old, while the Earth is only 4.6 billion years old. How many civilisations could have arisen and fallen in this time span before the formation of the Earth?”

The theory, coupled with the practical discovery that the galaxy teems with Earth-like planets, has triggered a revolution in the scientific community. It is believed that most of the planets in the habitable zone are home to life forms very similar to ours. In the Atacama Desert, Chile, in August 2016 astronomers announced the discovery of a planet orbiting the closest star to our solar system, namely Proxima Centauri. The planet in question, Proxima B, is Earth-like and close enough to its star to harbour life. Proxima B is one of the most interesting and recently discovered exoplanets: it is about 1.3 times larger than Earth. Scientists believe it is rocky and may be similar to our planet. Proxima B may be habitable and is being studied with telescopes in more detail; images will be available over the next ten years.

Despite the immense distance, an ambitious programme to study it by spacecraft is underway. The Breakthrough Starshot project is the brainchild of Israeli citizen Russian philanthropist Jurij Milner and the late, famous cosmologist, Stephen Hawking (1942-2018). Milner said: “For the first time in the history of mankind, we will not only be observing the stars, but we will also be able to reach them”. The goal of Breakthrough Starshot is to send small probes a few centimetres in size to the nearby planet. The microchip will be fitted with a sort of parachute propelled by laser beams that will inflate the sails and deposit the probe on the nearest star. The device will travel at cruising speed, but can accelerate up to 20% of the speed of light so that it will easily reach the nearest stars. Although travelling at very high speeds, the probes will take twenty years to complete the journey.

Light travels at a finite speed: the sun rays take about eight minutes to reach the Earth. Many bodies are thousands or millions or billions of light years away.

In recent years, an increasing number of astrophysicists have speculated that mankind could unravel the mysteries of interstellar space travel much sooner than previously thought. They believe the key is to use a theoretically possible structure known as wormhole: a space-time curve theorised by Albert Einstein that could make interstellar travel times not only shorter but almost instantaneous. Wormholes are capable of curving space and would play a key role in space travel. They are studied in the current theory of gravity and general relativity. A wormhole is a tunnel that connects two separate ends that are folded on themselves: they are commonly called stargates, because they enable travel over considerable distances in less time than light would take, but without exceeding the speed of light. In theory, spacecraft capable of creating wormholes could travel to distant exoplanets in a few hours or a matter of seconds, respecting Einstein’s laws.

Mount Palomar, California, October 6, 2013: a red supergiant star in the constellation Pegasus. ten times larger than the Sun, exploded in a colossal supernova. For the first time, scientists could witness the death of a supergiant star in real time but, as the dying star was 160 million light years from the Earth, astronomers witnessed an event that had happened 160 million years ago.

One of the basic concepts of astronomy is that almost everything we see happened in the past because light does not travel instantaneously. A supernova is a stellar explosion that wipes out all the planets around it, including any civilisations or life forms, but the whole process occurred in the distant past. The violent death of the star in the constellation Pegasus provides dramatic confirmation that the Universe is an ancient and dynamic unit.

Billions of years from now, our star, the Sun, will turn into a supernova and the day is inexorably approaching when we should migrate to another habitable planet. It is not reassuring that the event will occur in the very distant future, as thinking about it today will save us tomorrow.

At La Silla Observatory in Chile, in August 2011 astronomers announced the discovery of a large Earth-like planet in the constellation Orion: the planet is in the habitable zone and the star around which it orbits is very similar to ours, thus making it suitable for hosting life. Hence the goal for us earthlings is to discover a stable solar system, like the one Earth is in.

However, specific resources are needed before practice can be developed from theory. In Los Angeles, in June 2019 TransAstra Corporation announced a partnership with NASA to launch a new project into space, namely asteroid mining. TransAstra Corporation was established in 2015, at the time when entrepreneur Elon Musk with SpaceX, Amazon founder Jeff Bezos with Blue Origin, and others were devising cheap and effective ways to travel to space. By having rockets capable of going into orbit cheaply, a business could be created in space like that of mining asteroids for precious metals of great value on Earth. They are called precious metals because they are becoming scarce on Earth. Hence where can we find asteroids?

Metals such as rare earth elements, gold, copper, zinc and platinum have been mined on Earth for thousands of years and are vital to civilisation, but their supply is limited partly because they do not come from our planet. The Earth originally was a mass in a molten state: many precious metals were drawn inwards. As a result of that process, the heavy elements sank to the centre of the Earth; as they cooled down, a crust of light materials was formed.

It is widely known that without the use of metals, technology and civilisation would not have existed. Luckily for us, it is estimated that about 3.8 billion years ago trillions of asteroids crashed into the Earth, depositing a layer of heavy metals on the Earth’s crust. Those materials did not come from the Earth: they were deposited on our planet by comets and asteroids that crashed into the Earth a long time ago. All the precious metals we mine on Earth come from celestial bodies. The bombardment of asteroids deposited metals that made the Bronze Age, the Iron Age and today’s technological civilisation possible, but many metals – including the rare earth elements needed for technology – are increasingly unavailable. This is the reason why many scientists and experts believe that the asteroid belt could come in handy. An asteroid, even a small one, has more rare earth elements than have been mined on Earth in the history of mankind: it is estimated that if extractions were made from even ten of the over six thousand asteroids – whose existence is recorded in the NASA database – they would produce resources equivalent to 1.5 trillion dollars. The asteroid belt could meet our civilisation’s needs for thousands of years and centuries to come.

The most sensible choice is to build spacecraft to find asteroids, extract material and take all the advantages and benefits.

Mountain View, California, April 2013: scientists at NASA’s Ames Research Centre discovered two new potentially habitable exoplanets, Kepler 62E and 62F, thanks to the Kepler Space Telescope. Planets 62E and 62F are called water worlds because they are covered by a global, all-encompassing ocean and are promising because they are located in the habitable zone and are covered by the ocean.

This means that in a phase of expansion and space migration, not only raw materials are needed, but also water which, once broken down and split into hydrogen and oxygen, could be used as fuel with the processes that are at the forefront, which I have analysed in some of my previous contributions.  

It is firmly believed that the search for life forms will further undergo a revolution very soon. On December 25, 2021, NASA launched the James Webb telescope, a space telescope for infrared astronomy, capable of analyses considered impossible until a few years ago, i.e. taking detailed, full-colour images of an exoplanet. The James Webb telescope is completely different from those in space. It gives the possibility to observe the reflected light of exoplanets and the electromagnetic spectrum in order to detect potential biological traces.

The future lies in research, the past in war. The certainty is many graves if we stand still.

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Finding the missing links of black-hole astronomy

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An accreting SMBH in a fairly local galaxy with very large and extended radio jets. © R. Timmerman; LOFAR & Hubble Space Telescope

A deeper understanding of black holes could revolutionise our understanding of physics, but their mysterious nature makes them difficult to observe.

The weirdness exhibited by black holes boggles the mind. Formed when a star burns all its nuclear fuel and collapses under its own gravitation, black holes are such oddities that at one time, even Einstein didn’t think they were possible.

They are regions in space with such intense gravitation that not even light escapes their pull. Once magnificent shining stars burn out and shrink to a relatively tiny husk, all their mass is concentrated in a small space. Imagine our Sun with its diameter of roughly 1.4 million kilometres shrinking to a black hole the size of a small city just six kilometres across. This compactness gives black holes immense gravitational pull.

Not only do they trap light, black holes can shred any stars they encounter and even merge with each other. Events like this release bursts of energy that are detectable from billions of light years away.

The Nobel Prize in Physics 2020 was shared by scientists who discovered an invisible object at the heart of the Milky Way that pulls stars towards it. This is a supermassive black hole, or SMBH, and it has a mass that is millions of times that of our sun. 

‘At the heart of every massive galaxy, we think there is a supermassive black hole,’ said astrophysicist Dr Kenneth Duncan at the Royal Observatory in Edinburgh, UK. ‘We also think they play a really important role in how galaxies form, including the Milky Way.’

Galactic monsters

Supermassive black holes are gravitating monsters of the Universe. ‘Black holes at the centre of galaxies can be between a million and a few billion times the mass of our Sun,’ said Professor Phillip Best, astrophysicist at the University of Edinburgh. 

They pull in gas and dust from their surroundings, even objects as large as stars. Just before this material falls in towards the black hole’s event horizon or point of no return, it moves quickly and heats up, emitting energy as energetic flashes. Powerful jets of material that emit radio waves may also spew out from this ingestion process.

These can be detected on Earth using radio telescopes such as Europe’s LOFAR, which has detectors in the UK, Ireland, France, the Netherlands, Germany, Sweden, Poland and Latvia.

Duncan is tapping LOFAR observations to identify the massive black holes in a project called HIZRAD. ‘We can detect growing black holes further back in time,’ said Duncan, ‘with the goal being to find the very first and some of the most extreme black holes in the Universe.’

LOFAR can pinpoint even obscured black holes. Duncan has used artificial intelligence techniques to combine data from LOFAR and telescope surveys to identify objects of interest.

Better instruments

Better instruments will soon assist in this task. An upgrade to the William Herschel Telescope on La Palma, Spain, will allow it to observe thousands of galaxies at the same time. A spectroscope called WEAVE has the potential to detect supermassive black holes and to observe star and galaxy formation.   

Radio signals indicate that supermassive black holes exist from as early as the first 5-10% of the Universe’s history. These are a billion solar masses, explained Best, who is the research supervisor.

The surprising part is that these giants existed at the early stages of the Universe. ‘You’ve got to get all this mass into a very small volume and do it extremely quickly, in terms of the Universe’s history,’ said Best. 

We know that following the Big Bang, the Universe began as an expanding cloud of primordial matter. Studies of the cosmic background radiation indicate that eventually clumps of matter came together to form stars. However, ‘The process where you form a blackhole as large as a billion solar masses is not fully understood,’ said Best.

Intermediate black holes

While studies of SMBHs are ongoing, Dr Peter Jonker, astronomer at Radboud University in Nijmegen, the Netherlands, is intrigued by the formation of black holes of intermediate scale.

He is studying the possible existence of intermediate black holes (IMBH) with the imbh project. He notes that supermassive black holes have been observed from when the Universe was only 600 million years old. Scientists estimate the overall age of the universe to be around 13.8 billion years.

‘The Universe started out like a homogenous soup of material, so how do you get clumps that weigh a billion times the mass of the sun in a very short time?’ said Jonker.

While supermassive black holes might consume sun-like stars (called white dwarfs) in their entirety, IMBHs should be powerful enough to only shred them, emitting a revealing flash of energy.

‘When a compact star, a white dwarf, is ripped apart, it can be ripped only by intermediate mass black holes,’ said Jonker. ‘Supermassive black holes eat them whole.’ There are strong indications that intermediate black holes are out there, but there’s no proof yet.

He is searching for flashes of intense X-ray energy to indicate the presence of an intermediate black hole. The problem is when signals are detected, the intense flashes last just a few hours. This means the data arrives too late be able to turn optical telescopes towards the source for observations.

‘This happens once in 10,000 years per galaxy, so we haven’t seen one yet in our Milky Way,’ said Jonker.

Jonker also seeks to observe the expected outcome of two black holes spinning and merging, then emitting a gravitational wave that bumps nearby stars. However, to discern these stars being jolted necessitates powerful space-based telescopes.

X-ray flashes

The Gaia satellite, launched in 2013, is providing some assistance, but a planned mission called Euclid will take higher resolution images and may help Jonker prove IMBHs exist. This satellite was due to be launched on a Russian rocket; it will now be launched with a slight delay on a European Ariane 6 rocket

Nonetheless, a small satellite – the Chinese Einstein Probe – is scheduled for launch in 2023 and will look out for flashes of X-ray energy that could signify intermediate black holes. Duncan in Edinburgh says that the search for intermediate black holes ties in with his own quest. ‘It can potentially help us solve the question of where the supermassive ones came from,’ he said.

Right now, physicists rely on quantum theory and Einstein’s equations to describe how the Universe works. These cannot be the final say, however, because they do not fit well together.

‘The theory of gravity breaks down near a black hole, and if we observe them closely enough,’ said Jonker, ‘Our expectation is that we will find deviations from the theory and important advances in understanding how physics works.’

The research in this article was funded by the EU. This article was originally published in Horizon, the EU Research and Innovation Magazine.  

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