The research team included Neha Yadav, a former PhD student at the Department of Physics, ProsenjitSen, Associate Professor at the Centre for Nano Science and Engineering (CeNSE), and AmbarishGhosh, Professor at CeNSE. The study was published in Science Advances.

An electron injected into a super fluid form of helium creates a single electron bubble (SEB) – a cavity that is free of helium atoms and contains only the electron. The shape of the bubble depends on the energy state of the electron. For instance, the bubble is spherical when the electron is in the ground state (1S). There are also MEBs – multiple electron bubbles that contain thousands of electrons, says IISc statement.

FEBs, on the other hand, are nanometre-sized cavities in liquid helium containing just a handful of free electrons. The number, state, and interactions between free electrons dictate the physical and chemical properties of materials. Studying FEBs, therefore, could help scientists better understand how some of these properties emerge when a few electrons present in a material interact with each other. According to the authors, understanding how FEBs are formed can also provide insights into the self-assembly of soft materials, which can be important for developing next-generation quantum materials. However, scientists have only theoretically predicted the existence of FEBs so far. “We have now experimentally observed FEBs for the first time and understood how they are created,” says NehaYadav, “These are nice new objects with great implications if we can create and trap them.”

Yadav and colleagues were studying the stability of MEBs at nanometre sizes when they serendipitously observed FEBs. Initially, they were both elated and sceptical. “It took a large number of experiments before we became sure that these objects were indeed FEBs. Then it was certainly a tremendously exciting moment,” says professor Ghosh.

The researchers first applied a voltage pulse to a tungsten tip on the surface of liquid helium. Then they generated a pressure wave on the charged surface using an ultrasonic transducer. This allowed them to create 8EBs and 6EBs, two species of FEBs containing eight and six electrons respectively. These FEBs were found to be stable for at least 15 milliseconds (quantum changes typically happen at much shorter time scales) which would enable researchers to trap and study them.

“FEBs form an interesting system that has both electron-electron interaction and electron-surface interaction,” Yadav explains.

There are several phenomena that FEBs can help scientists decipher, such as turbulent flows in superfluids and viscous fluids, or the flow of heat in superfluid helium. Just like how current flows without resistance in superconducting materials at very low temperatures, superfluid helium also conducts heat efficiently at very low temperatures. But defects in the system, called vortices, can lower its thermal conductivity. Since FEBs are present at the core of such vortices – as the authors have found in this study – they can help in studying how the vortices interact with each other as well as heat flowing through the superfluid helium.

“In the immediate future, we would like to know if there are any other species of FEBs, and understand the mechanisms by which some are more stable than the others. In the long term, we would like to use these FEBs as quantum simulators, for which one needs to develop new types of measurement schemes,” Ghosh announces.

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Keywords: Scientists, IISc, Indian Institute of Science,Species, Few electron bubbles (FEBs),Ssuperfluid, Helium, FEBs,Energy, Electrons, Material influence, Centre for Nano Science and Engineering (CeNSE), Science Advances

In a recent study, the researchers from the Indian Institute of Technology Bombay (IIT Bombay) have used a new catalyst for extracting hydrogen from water. Researchers have demonstrated how a magnetised catalyst can speed up hydrogen productionwhile bringing down the energy cost.They showed that their chosen catalyst had increased the speed of producing hydrogen and reduced the energy required to do so, compared to previous studies.

To extract hydrogen from water, researchers insert two electrodes across the water and pass current, which can separate the hydrogen from water, a process called electrolysis of water. Earlier studies have shown that metals like Platinum, Rhodium, and Iridium speed up electrolysis. “Although these metals work well, industrial systems don’t prefer them because they are expensive,” says Prof Chandramouli Subramaniam of IIT Bombay and an author of the study. The study has used a compound consisting of cobalt and oxygen to achieve the same goal at a much lower cost. While earlier researchers focused on developing new catalysts for the electrolysis of water, the authors of the present study concentrated on an alternative approach.

To achieve the increased energy efficiency, the researchers turned to less costly metal cobalt,already known for speeding up electrolysis. They decorated carbon nanoflorets,nanocarbon structures arranged like a marigold flower with cobalt oxide particles and placed these nanoflorets in the water. An electric field applied through the cobalt oxide to water molecules results in the electrolysis of water. Although cobalt oxide is a well-known electrochemical catalyst, it requires a high amount of energy and produces hydrogen at a low speed.

To increase the speed of electrolysis, the researchers did not rely on the electric field alone. Magnetic fields, which are related to electric fields, can play a crucial role in these reactions. The researchers showed that if they introduced a small fridge magnet near their setup, the reaction speed increased about three times. Even after removing the external magnet, the reaction still took place about three times faster than in the absence of the magnetic field. “This is because the catalyst we have designed can sustain the magnetisation for prolonged periods, the key being the development of a synergistic carbon-metal oxide interface,” explains JayeetaSaha, the author of the study. “A one-time exposure of the magnetic field is enough to achieve the high speed of hydrogen production for over 45 minutes,” she adds.

It is easy to integrate accessible house-magnets into the existing designs at a low cost. “We can directly adopt the modified setup in existing electrolysers without any change in design or mode of operation of the electrolysers,” says Ranadeb Ball, another author of the study.

“The intermittent use of an external magnetic field provides a new direction for achieving energy-efficient hydrogen generation. Other catalysts can also be explored for this purpose,” says Prof. Subramaniam.

Once the hydrogen is produced in large amounts, it can be packed off in cylinders and used as a fuel. If their efforts are successful, we might be looking at an environmentally friendly fuel, hydrogen, replacing petroleum, diesel, and compressed natural gas (CNG) in the future.

The study was supported by the Science and Engineering Research Board (SERB), Department of Science and Technology (DST), the Council of Scientific and Industrial Research (CSIR),and the Industrial Research and Consultancy Center, IIT Bombay. It was published in the journal ACS Sustainable Chemistry & Engineering.

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Keywords: Hydrogen,Environment-friendly, Fuel, Oxygen, Gasoline, Indian Institute of Technology, IIT Bombay, Catalyst, Energy,SERB, DST,CSIR,ACS Journal

Galaxies like the one we reside in, the Milky Way, consist of discs containing stars, molecular and atomic hydrogen, and helium. The molecular hydrogen gas collapses on itself in distinct pockets, forming stars, its temperature was found to be low –close to 10 kelvin, or -263 ºC and thickness is about 60 to 240 light-years. The atomic hydrogen extends both above and below the discs.

However, more sensitive observations in the past two decades have surprised astronomers. They have estimated that molecular hydrogen extends farther from the disc in both directions, up to about 3000 light-years. This gaseous component is warmer than the one straddling the disc and has comparatively lesser densities, thus escaping earlier observations. They called it the ‘diffuse’ component of the molecular disc.

How much of the total molecular hydrogen is this diffuse component of the disc remains unclear. In a new study, a researcher from Raman Research Institute (RRI), Bengaluru, an autonomous organisation of the Department of Science and Technology (DST), Government of India, has carried out mathematical calculations on the computer and used publicly available astronomical data of a nearby galaxy to pin down the ratio of the narrow and diffuse gaseous components. The study, funded by the DST, Government of India, was published in the journal Monthly Notices of the Royal Astronomical Society.

“The molecular hydrogen gas converts to individual stars under the pull of gravity, thus holding clues to the star formation processes and the evolution of the galaxy,” said Narendra Nath Patra, the researcher. If a significant part of the gas extends beyond the thin disc of a few hundred light-years, it may explain why astronomers also observe stars at a few thousand light-years perpendicular to the galactic disc. It is also essential to understand why the gas has two components, he says, and maybe tell-tale signatures of supernovae or exploding stars.

For the study, Narendra focussed on a single galaxy about 20 million light-years away from the Milky Way. The distance is relatively small compared to the size of the universe, more than 10 billion light-years. The galaxy’s proximity makes it easier to observe with telescopes, and spectral lines of carbon monoxide (CO) are available for public research. “The carbon monoxide molecule is known to accurately trace molecular hydrogen, whose spectral lines are more difficult to observe,” explains Narendra. “The galaxy I chose is very much like the Milky Way and is therefore interesting for studying the ratio of diffuse and thin components of the disc,” he adds.

The researcher used the observed spectral lines of the CO molecule to infer the three-dimensional distribution of both the narrow disc component and the diffuse component of molecular hydrogen. Estimating how the ratio of the two components varies with the distance away from the centre of the galaxy, he found that the diffuse component makes up about 70 percent of the molecular hydrogen, and this fraction remains roughly constant along the radius of the disc. “This is the first time that such a calculation has been done for any galaxy,” he asserts.

The method, although new, relies on calculations that can be carried out on computers with the help of publicly available data. Hence, Narendra is already on his way to employing it on other nearby galaxies. “Currently, our group at RRI is employing the same strategy for a set of eight galaxies whose CO lines are available,” he says. “We want to test whether the results were one-off for the galaxy I chose or if there is a pattern,” he pointed out. The search is on, and we may expect the results this year.

The Eni Awards 2020 will be presented in an official ceremony at the Quirinal Palace in Rome on 14 October 2021. President of the Italian Republic, Sergio Mattarella will preside over the ceremony.

The Energy Frontiers Award has been conferred for Prof. Rao’s work on metal oxides, carbon nano-tubes, and other materials and two-dimensional systems, including graphene, boron-nitrogen-carbon hybrid materials, and molybdenum sulfide (Molybdenite – MoS₂) for energy applications and green hydrogen production.

The Eni Award is awarded by the Italian oil and gas company, Eni. Launched in 2007, the award has become internationally recognized over the years in the field of energy and environmental research. It aims to promote better use of energy sources and encourage new generations of researchers in their work. It bears witness to the importance that the company places on scientific research and innovation. It includes a cash prize and a specially minted gold medal.

Professor Rao has been working on hydrogen energy as the only source of energy for the benefit of the entire humankind. His work included hydrogen storage, photochemical, electrochemical and solar production of  hydrogen, and non-metallic catalysis. He has developed some highly innovative materials by working in photo dissociation of water, thermal dissociation, and electrolysis activated by electricity produced from solar or wind energy. The same or related materials have also been shown to have beneficial properties for the construction of hydrogen storage systems and super capacitors with high specific power and an increased number of charge-discharge cycles. The latter are energy storage devices, similar to batteries, which will become an increasingly important part of the renewable energy sector.

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Keywords: science and technology, innovation, hydrogen, nobel award, Eni award, international awards, energy, research, atomic research, gases, india, worldwide, rome, 2020, October, researcher.

Harikrishnan Aravindakshan, Prof. Amar Kakad, and Prof. Bharati Kakad from the Indian Institute of Geomagnetism (IIG), an autonomous institute under the Department of Science and Technology, have developed the theory. Prof. Peter Yoon of the University of Maryland, USA also joined the Indian scientists.

The theory solves every bit of uncertainty regarding the conflict between the observations from Magnetospheric Multiscale (MMS) Mission. It’s a NASA robotic space mission to study the Earth’s magnetosphere and theoretical predictions.

The scientists have developed a theory that helps understand the complicated nature of Sun-Earth interactions happening in the magnetosphere, the space around Earth that is controlled by the Earth’s magnetic field.

Using their theory, the scientists are now working towards a detailed study of the ion hole structures observed in various space and astrophysical environments.

They have completely ruled out the necessity of the upper limit in the temperature ratio between ions and electrons for generation of a special kind of wave called Bernstein Green Kruskal (BGK) waves, named after the scientists who predicted this wave. They revealed that the electrons that are not part of ion hole dynamics also play a vital role. The work has been published in the journal, Monthly Notices of the Royal Astronomical Society.

On 2 November 2017, NASA’s expedition to unlock Sun-Earth interaction’s complicated nature, the MMS spacecraft, observed negative monopolar potential, electric field potentials which can be visualized in the form of single-humped, pulse-type structures.

The scientific community suddenly recognized its importance, and several publications were presented. But none of the available theories could explain the characteristics of these structures due to the exotic background conditions.

The new theory developed by the IIG team now provides a better understanding of their characteristics and sheds light on the generation of these structures leading to the unravelling of nature’s greatest mystery that causes the phenomena, plasma transport and heating of plasma, the fourth state of matter after solid, liquid, and gas, which is the most natural and widely observed state of matter in the entire universe.

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Keywords: Science & Technology, Science, Discovery, Innovation, Invention, Matter, Galaxy, Plasma, Fourth Matter, Spacecraft, Space, IIG, Sun, Earth, Astronomy.

IIT Delhi

Optics and photonics is the study of the fundamental properties of light and harnessing them in practical applications. To list a few, the areas covered under optics and photonics include Optical imaging, Optical metrology, Sources and detectors of light, Lasers, Fiber optics, Optical communication, Optical sensors, Colour of light, Vision optics, Remote sensing, Illumination, Diffractive optics, Adaptive optics, Holography, Fourier optics, Optical image processing, Opto-electronics, Optical data storage, Optical computing, Microscopy, Bio-medical optics, Nonlinear optics, IR optics, Terahertz optics, Photonic circuits, Nano-photonics, Plasmonics, Ultra-fast optics, Photonic quantum technologies etc.

The Optics and Photonics Centre, IIT Delhi will seek collaboration with establishments such as the Defence Research and Development Organisation (DRDO), Council of Scientific and Industrial Research (CSIR), Department of Atomic Energy (DAE), Indian Council of Medical Research (ICMR) and industry to undertake R&D in the areas of importance for them. DRDO is already collaborating in this area through a vertical in Photonics in the Joint Advance Technology Centre (JATC) at IIT Delhi.

“As the spread of photonic technology and its usage is increasing, there would be many opportunities for such collaborations including setting up of start-ups. Apart from this, the Centre will play a pivotal role in the near future development of photonics-based quantum technologies, for next generation computing, secure communications etc.Sustained linkages with industry will also be developed and established,” said Prof Joby Joseph, Coordinator, Optics and Photonics Centre, IIT Delhi.

On the teaching side, the Centre will focus on doctoral and postgraduate programmes including special programs for industry professionals. Innovation and translation of research into products would be very important for the Centre. It will also encourage and help students in entrepreneurial efforts and connect them with suitable investors through due processes at the Institute.

IIT Delhi has been known for its contributions in Optics in India and abroad. Many faculty members in Physics Department, Electrical Engineering, Centre for Sensors, Instrumentation and Cyber Physical System Engineering (SeNSE) and several other academic units are engaged in Optics &Photonics R&D.Over the years, four faculty members of the Physics Department have been recognized with the coveted Shanti Swarup Bhatnagar Prize for their work in optics and photonics.

Prof. Anurag Sharma, JC Bose Fellow, Dept. of Physics, IIT Delhi said, “The Centre will synergize and significantly enhance the activities in Optics and Photonics at IIT Delhi. This is particularly important in view of the strong interdisciplinary nature of the subject.”

Optics and photonics have become extremely important today as enabling technologies, and have immense applications in diverse fields such as communication and information processing; quantum information and computing; energy harvesting and green energy; lighting- particularly solid-state lighting; imaging- particularly bio-imaging; and several engineering fields- aerospace, civil and environment, agriculture, micro-nano fabrication, automotive engineering, research and industrial instrumentation, surveillance and offence in the military.

Many agencies such as the DRDO, CSIR, DAE, Department of Space and industries are increasingly turning towards optics and photonics for technological solutions.

Many new application areas are emerging day-by-day. In recognition of the importance of this, the UN declared 2015 as the International Year of Light and Light-based Technologies and since 2018, May 16 is celebrated as the International Day of Light.

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Keywords: R&D, Innovation, Ooptics, Photonics, Indian Institute of Technology, IIT Delhi, Optics and Photonics Centre, light, Optical imaging, Optical metrology, Lasers, Fiber optics, Optical communication, Optical sensors, Remote sensing, Illumination, DRDO, CSIR, DAE, ICMR, Joint Advance Technology Centre (JATC)

”We are honoured to announce the Sunanda and Santimay Basu Chair in Astrophysics at Ashoka University. Their pioneering work in the area of ionospheric scintillation have been critical to understanding of ionospheric space weather. The Chair is a step towards encouraging cutting edge work in Astrophysics and the setting up of Centre for Astrophysics to nurture Indian astrophysicists who would follow in their footsteps, said Prof. Malabika Sarkar, Vice-Chancellor, Ashoka University.”

Speaking on the announcement of Sunanda and Santimay Basu Chair in Astrophysics, renowned physicist Dr. Sunanda Basu said ”I am delighted to announce an academic chair in astrophysics at Ashoka University. Over the past few years, Ashoka University has emerged as one of the leading liberal arts and sciences Universities in India. I am confident that this position will create a nucleus for a vibrant centre in astrophysics at Ashoka University and encourage world class research in the subject at the University.”

Sunanda and Santimay Basu are internationally recognized experts in the area of ionospheric scintillation, having made cutting edge research contributions to every aspect of the field encompassing diverse natural irregularity formation processes at high, middle and low latitudes, as well as artificial turbulence generation through high-power high frequency (HF) radio wave interactions. These scintillations, now known generically as ionospheric space weather, are caused by plasma density irregularities in near-Earth space, and are responsible for creating errors in space-based communication and navigation systems such as GPS. Such errors are much enhanced during magnetic storms on Earth, which follow transient events on the sun, like solar flares or coronal mass ejections.

This scientist couple started their research careers in India and continued in the US for many decades. Santimay Basu passed away in 2013 and Sunanda has continued her career, with greater emphasis on philanthropy within the US and in developing countries, including Africa. In 2014, she endowed a gold medal and prize in memory of her husband Santimay, to be given to an early-career scientist at the General Assemblies of the International Scientific Radio Union (URSI).

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Keywords: Physics, Sunanda and Santimay Basu Chair, Ionospheric Scintillation, Ionospheric, Space Weather, Centre for Astrophysics, Astrophysicists, Ashoka University

DrAmitaRawat and Prof UdayanGanguly from the Department of Electrical Engineering, Indian Institute of Technology, Bombay (IIT Bombay), in collaboration with researchers from IMEC, Leuven, Belgium, have experimentally validated their previously proposed method to estimate the change in performance of an electronic circuit caused by manufacturing variations. This is the first time that the experimental validation of variations predicted using physics-based modeling has been reported. The predictions can be integrated with circuit design software, thus making it possible to design better-performing circuits. This work was partially funded by the Indian Institute of Technology Nano Fabrication Lab (IITBNF Lab), the Ministry of Human Resource Development (MHRD), and the Department of Science and Technology (DST).

Patterns are drawn using UV light on semiconductor chips to mark the channel, gate, interconnects, and other circuit components. Patterns with lines and spaces smaller than 10 nanometer tend to have fluctuations of about a nanometer. It is also challenging to place dopant atoms perfectly. The gate metal has nanoscale crystals that are not oriented uniformly in the same direction leading to different atomic interfaces between metal crystal and gate insulator. These local physical variations can significantly affect the electrical properties of the transistor. “For example, the variation in how metal is deposited affects the value of the gate voltage at which the transistor starts conducting current,” explains Dr Rawat, the lead author of the study.

As the building blocks of electronic circuits approach the atomic scale, the physical variations become substantial compared to the component dimensions. In commercially-used design and simulation softwares, circuit performance is inexactly evaluated based on simple variation in electrical properties of the transistor that is increasingly inaccurate as transistors shrink. “We provide process specific physics-based estimates of the electrical variation. It enables a more accurate evaluation of the circuit performance,” says Dr Rawat. “The designers can also get an idea of how the variation will alter if they change from one manufacturing process to another,” she adds.

To find the influence of the physical variations on the circuit performance, engineers first need to evaluate its effect on the transistor’s electrical properties. Currently, computational methods are used to study the structures of a few hundreds of transistors to find variations in electrical properties. With hours of costly simulations needed to calculate each transistor’s parameters, the process is computationally expensive and time-consuming. “Also, this method does not provide a simple, intuitive model connecting the structural variations to electrical variations of the transistors, necessary for the circuit designers,” comments Prof Ganguly.

“Our team developed the theoretical modelling of variability over nine years and three PhD theses. The journey is chronicled in a magazine article in IEEE Nanotechnology Magazine. Now our work has reached the experimental validation phase,” says Prof Ganguly.

The researchers created a mathematical model that accurately predicts variations in the transistor electrical properties based on the changes in the physical parameters, such as fluctuations of the pattern lines or metal nanocrystal orientation. The same model works for any manufacturing process. They used this transistor variation data to create a ‘variabilityaware’ transistor model to be used in a commercial design and simulation software. Thus circuits designed using this model capture the actual variability due to the manufacturing process, and designers can get an accurate estimation of the circuit performance. “The beauty of our platform is that the circuit performance prediction can be made available commercially, without significantly adding to the cost,” comments Dr Rawat.

“In addition to making it easier to design better-performing circuits, the proposed method can also provide feedback to the foundry team for improving their processes,” says Dr Rawat. The process designer can determine which process dependent inputs give the desired physical variability parameters. “It is like building a bridge between the circuit designers and the process team.”

In the current study, the researchers used their model to predict the physical variations for the 14nm technology process. They compared these values with the experimentally measured physical variations and found them to match well. They also estimated the variations in electrical properties of the transistor, and these agreed with the experimentally measured variations of a cluster of 250 transistors made with the 14nm technology. The worst and best case errors were within acceptable limits. “Such elaborate experimental validation has not been reported earlier,” remarks Dr Rawat.

The researchers plan to provide this framework as a technology package to be plugged into the circuit design software. “We need to collaborate with foundries to access the latest data of manufacturing processes they use. We can create the process-specific package and get it validated from the foundry. It can evolve into an industry standard,” said DrRawat.

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Keywords: circuit performance, IIT Bombay, circuit design, software, IITBNF Lab, MHRD, Department of Science and Technology, DST.

“Moon will hide Mars behind it, just like it hides the Sun during a solar eclipse,” says Arvind Paranjpye, Director, Planetarium, Nehru Centre, Mumbai, and a member of the Public Outreach and Education Committee (POEC) of Astronomical Society of India.

Called an ‘occultation’ in astronomical parlance, the conjunction of a planet with the Moon was seen as samagama (union) in Indian astronomical tradition. As Mars goes behind the Moon, they concluded that Moon is nearer compared to Mars in ancient times. Such occultation events, between Moon and the planets and between two planets, gave the ancient astronomers opportunity to work out the relative distances of the celestial objects.

On April 12, 2021, was a new moon. By April 17, in its waxing phase, about 18 % of Moon’s disc is illuminated. On this day, the angle between the Sun and the Moon will be nearly 60°. “We can see the glorious setting Sun plunging towards the western horizon, and halfway up, the crescent Moon. Further, on the eastern direction of the Moon, towards the dark disc side, we can easily spot the red Mars,” says Arvind Paranjpye.

The sunset will occur earlier in Eastern India, including Andamans, compared to the Western parts of India. Hence for those in the Eastern region, the occultation will occur much after the sunset. “For India, this will be a mixed bag event. At locations in western India, the occultation will begin when the Sun is still above the horizon,” says Arvind Paranjpye.

In Delhi, at evening 6 pm on April 17, the Sun will be about 9 degrees above the horizon.  As we continue to observe, the separation between Mars and the Moon will decrease. Finally, precisely at 18:02:07, Mars would go behind the dark disc of the Moon, disappearing from our sight. It will take about 9 seconds for the Mars to be completely eclipsed by the dark disc of the Moon. After about an hour, 19:04:10, Mars will surface at the other side, the bright crescent of the Moon. Timings of disappearance and reappearance of Mars at each location would differ. “We have computed the precise timings for 124 locations in India, which can be accessed at our website “, says Arvind Paranjpye. The details can be accessed at https://astron-soc.in/outreach/activities/sky-event-related/moonmars2021/#info.

We need to choose a spot carefully to observe this spectacle, says Arvind Paranjpye. It has to be a place with an unhindered view towards the West. One must reach the selected site by around 530 and stand facing the western sky. “Although, the spectacle is not a rare one, last time the occultation of Mars by the Moon, visible over India in the evening, was on May 10 2008,” says Arvind Paranjpye.

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Table 1

Timings of disappearance and reappearance at major locations: A blank under the Sun altitude indicates that the Sun is well below the horizon

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The POEC of the Astronomical Society of India will webcast this event live from various locations. Visit https://astron-soc.in/outreach/activities/sky-event-related/moonmars2021/ for a list of those who will webcast it live.

Quasars are extremely luminous cores of distant galaxies that are powered by supermassive black holes. Quadruply imaged quasars are rare, and the first quadruple image was discovered in 1985. Over the past four decades, astronomers had found about fifty of these “quadruply imaged quasars” or quads for short, which occur when the gravity of a massive galaxy that happens to sit in front of a quasar splits its single image into four.

The study by Gaia Gravitational Lenses Working Group (GraL) of astronomers, which included scientists from Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, an autonomous institute of Department of Science and Technology, spanning only a year and a half, demonstrates the power of machine-learning to assist astronomers in their search for these cosmic jewels. It has been accepted for publication in ‘The Astrophysical Journal’.

Caption: This diagram illustrates how quadruply imaged quasars, or quads for short, are produced on the sky. The light of a distant quasar, lying billions of light-years away, is bent by the gravity of a massive galaxy that happens to sit in front of it, as seen from our point of view on Earth. The bending of the light results in the illusion that the quasar has split into four similar objects surrounding the foreground galaxy. Image credit: R. Hurt (IPAC/Caltech) / The GraL Collaboration.

“The quads are gold mines for all sorts of questions. They can help determine the expansion rate of the universe and help address other mysteries, such as dark matter and quasar ‘central engines’,” says Daniel Stern, lead author of the new study and a research scientist at the Jet Propulsion Laboratory USA.

Cosmological Dilemma

In recent years, a discrepancy has emerged over the precise value of the universe’s expansion rate, also known as Hubble-Lemaître’s constant. Two primary means can be used to determine this number: one relies on measurements of the distance and speed of objects in our local universe, and the other extrapolates the rate from models based on distant radiation left over from the birth of our universe called the cosmic microwave background. The problem is that the numbers do not match. The quasars lie in between the local and distant targets used for the previous calculations. The new quasar quads, which the team gave nicknames such as “Wolf’s Paw” and “Dragon Kite,” will help in future calculations of Hubble-Lemaître’s constant and may illuminate why the two primary measurements are not in alignment.

Caption: Four of the newfound quadruply imaged quasars are shown here: From top left and moving clockwise, the objects are: GraL J1537- 3010 or “Wolf’s Paw;” GraL J0659+1629 or “Gemini’s Crossbow;” GraL J1651-0417 or “Dragon’s Kite;” GraL J2038-4008 or “Microscope Lens.” The fuzzy dot in the middle of the images is the lensing galaxy, the gravity of which is splitting the light from the quasar behind it in such a way to produce four quasar images. By modeling these systems and monitoring how the different images vary in brightness over time, astronomers can determine the expansion rate of the universe and help solve cosmological problems. Image credit: The GraL Collaboration.

Humans and Machines Working Together

“Machine learning along with Augmented Intelligence (AI) tools was key to our study, but it is not meant to replace human decisions,” explains Krone-Martins, Lecture at University of California. “We continuously train and update the models in an ongoing learning loop, such that humans and the human expertise are an essential part of the loop,” said Krone-Martins, one of the authors of the study.

In the new study, the researchers used data from Wide-field Infrared Survey Explorer (WISE) to find likely quasars and then used the sharp resolution of Gaia to identify which of the WISE quasars were associated with possible quadruply imaged quasars. The researchers then applied machine-learning tools to pick out which candidates were most likely to multiply imaged sources and not just different stars sitting close to each other in the sky. Follow-up observations by Keck Observatory at U.S. state of Hawaii; Palomar Observatory at California, United States, the New Technology Telescope operated by the European Southern Observatory, and Gemini-South Observatory at Hawaii confirmed which of the objects were indeed quadruply imaged quasars lying billions of light-years away.

Confirming candidates with spectral data

Priyanka Jalan, a Ph.D. student at Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, India, and Jean Surdej, Visiting astronomer at ARIES, have been very actively involved in the reduction and analysis of spectra of quasar components obtained from large ground-based telescopes.

“Many two lensed images of a single quasar have been found in the past, however, finding four lensed images is like searching for a cloverleaf in a large green field. It is thus appropriate to name those mirages “cosmic clover-leaves,” says Jean Surdej, member of GraL and Professor at the University of Liege, Belgium.

Further astrophysical studies of these new cosmic clover-leaves and other multiply imaged quasars with the 3.6m Devasthal Optical Telescope (DOT) and the upcoming 4m International Liquid Mirror Telescope (ILMT) facilities operated by ARIES should lead to an independent determination of the age of the Universe and its expansion rate.

“Considering the excellent seeing conditions at Devasthal and frontline back-end instruments, candidate multiply quasar sources can be most suitably observed with the 3.6m DOT,” said Brijesh Kumar, Astronomer-in-charge of 3.6m DOT Facility.