Global warming puts whales in the Southern Ocean on a diet

In the autumn, when right whales swim towards the coasts of South Africa, they ought to be fat and stuffed full. But in recent years, they have become thinner because their food is disappearing with the melting sea ice.

Peer-Reviewed Publication

AARHUS UNIVERSITY

 

IMAGE: A SOUTHER RIGHT WHALE MOTHER WITH IT'S CALF SWIMMING IN THE WATERS NEAR THE COAST OF SOUTH AFRICA. view more 

CREDIT: FREDRIK CHRISTIANSEN

In the month of June, when winter bites in the southern hemisphere and the sea around the Antarctic freezes over, right whales swim north. Many of them gather in the bay outside the town of Hermanus in South Africa. 

Here, the warmer South African water is perfect for mating or raising newborn calves.  However, there is no food for the whales, and all winter long the right whale mothers use up their fat reserves to produce milk for their calves.

It is therefore extremely important that the whales eat a lot and fatten up in the cold waters around the Antarctic throughout the summer. But it seems there is not enough food. The whales arriving at the coasts of South Africa are thinner than they used to be.

This is the result of new research from Aarhus University. Since the researchers started to measure right whales in the 1980s, the whales have become increasingly thinner. This is explained by Fredrik Christiansen, a senior researcher at the Department of Ecoscience at Aarhus University, who is behind the new results.

"Right whales are 25 per cent thinner than they were in the 1980s. This is bad for the whale population, because it means that the newborn whale calves have a higher risk of dying. Fortunately, the right whales in the Southern Ocean are not endangered, but if this continues, they could become so,” he says.

When the ice melts, food disappears
When winter comes, and the cows leave the Antarctic and swim north, they have to cope for several months without food. Several months in which they eat into the fat reserves they have built up through the warm and light summer season.

Throughout the summer, right whales swim around beneath the sea ice, open their mouths to take in seawater, krill and water fleas. The baleen inside their mouth is a sort of a giant filter and it filters the small animals from the salt water. This allows the whales to eat huge amounts of food without using a lot of energy.

But the large shoals of krill are shrinking – and this means that the whales can’t fatten up before winter as they used to," explains Fredrik Christiansen. 

“The shoals of krill live on phytoplankton, which thrive best in the cold waters around the Antarctic. Here – like plants on land – they transform sunlight into energy. Rising sea temperatures mean there is less phytoplankton, fewer krill and thus less food for the whales.

Instead, the whales forage for food further north, where there is another and less energy-rich form of krill. 

“Further north, there’s less food for these small crustaceans. Therefore, they’re not as big and fat as the animals living beneath the Antarctic sea ice,” he says.

How to weigh a whale
How exactly do scientists know that the whales have become thinner? Do Fredrik Christiansen and his colleagues lift the huge animals out of the water with oversized weighing scales? No, he explains. Instead, the researchers have invented a method to work out the weight of the whales based on photographs taken by drones.

“Right whales like to lie flat on the sea surface. This makes them easy to photograph from above. When the drone has taken some photographs – and we know the height of the drone – we can calculate the size of the animal," he explains.

However, in order to know the weight of the whale, it is necessary to know the volume of the whale – not just the length and width. But because scientists like Fredrik Christiansen have observed many right whales rolling around on the sea surface over the years – and thereby have been able to measure their size – the scientists now know the relationship between length, width and volume of the whales.

"We calculate the volume using the drone photographs – and when we know the volume, we more or less know the weight. In this way, we can see that the whales have become thinner over the past 30 years – and that’s serious. The weight of the mothers has a huge impact on their calves,” he says. 

Small and weak whale calves
Thirty to forty years ago, the southern right whale had calves every three years on average. But this is no longer true, explains Fredrik Oscar Christiansen.

“In the 1980s, researchers observed that the right whales off the coast of South Africa gave birth to a new calf every three years. But because it’s now difficult for them to fatten up during summer, this has fallen to every five years. This means that the population is growing significantly more slowly.

And not only do the whale calves come more rarely. The calves born today are smaller and grow more slowly.

“The amount of fat on the whale mother is directly linked to how much energy she can give to her calf through her milk. When the mother is thin, the calf gets less energy and grows more slowly,” he says.

The researchers have discovered that the northern right whales in the waters off Canada and the northern US are not growing quite as big as before. This is possibly because the calves are born smaller. According to the researchers' calculations, a whale born in 2019 will be one metre shorter on average when it is fully grown than a whale born in 1981.

"Small calves have a higher risk of dying. They’re more vulnerable if a killer whale attacks.” 

Hunted close to extinction
Right whales were given their name because they were considered the "right" whales to catch. People began hunting the large whales as early as in the 14th century, and for hundreds of years, they were hunted fiercely in both northern and southern parts of the Atlantic.

Oil from the whales' fat was one of the most important sources of energy. Train oil, which the oil used to be called, became a fuel in lamps – both for indoors and for street lights. The demand for train oil was also one of the most important reasons why Denmark colonised Greenland in the 18th century. 

Around 1900, train oil was replaced by another more efficient energy source: crude oil. The black gold pumped up from the underground meant that whale hunting was no longer profitable.

The southern right whale is one of the species that benefitted from the end of whaling. For more than 100 years, the population has been allowed to grow large and healthy again. And this is not just good for the whales, but also for the entire Southern Ocean ecosystem.

Because the whales bring nourishment to areas of the sea with little food.

Extremely important for the marine ecosystem
The sea around the Antarctic where the right whales come to eat has more life than any other sea on the planet. Despite the fact that the area only contains five per cent of the Earth's sea water, 20 per cent of all marine life lives in the area.

The many hours of sunshine in the summer, turbulent sea currents and the low temperature are perfect for teeming life.

The light makes marine algae grow explosively. The sea currents swirl the algae and nourishment around so that krill and plankton can gorge themselves. When full, the small crustaceans reproduce and form gigantic swarms. In some places, there may be as many as 35,000 krill in one cubic metre of water.

The right whales – and many other animals – stuff themselves with the abundance of krill, but unlike many other species, the whales migrate thousands of kilometres north to overwinter. 

“The whales are extremely important for the parts of the sea where there is not much food. When the whales die, their huge bodies sink to the bottom. In the depths, they become food for a whole ecosystem of eel, sharks, crabs, lobsters, worms and microorganisms,” says Fredrik Christiansen.

So, if the whales disappear, it will have major consequences for many other animals.

“The whales are an apex predator. When an animal at the top of the food chain disappears, it has a cascade effect. Animals throughout the food chain will be affected if the whales are no longer there. From sharks to bacteria,” he concludes.

All photos used in this article have been taken by drones. It's the same photos that the researchers use to calculate the weight of the whales.

The southern right whales used to give birth every third year, but because of the lack of food five years passes between every birth.

CREDIT

Fredrik Christiansen.

JOURNAL

Scientific Reports

DOI

10.1038/s41598-023-30238-2 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Decadal decline in maternal body condition of a Southern Ocean capital breeder

Clarifying the trends of tropical cyclones over our oceans towards better predicting and coping with their destruction

Peer-Reviewed Publication

INSTITUTE OF ATMOSPHERIC PHYSICS, CHINESE ACADEMY OF SCIENCES

 

IMAGE: OBSERVED DECADAL SHIFTS AND TRENDS IN GLOBAL TROPICAL CYCLONE ACTIVITIES FROM 1980-2021 view more 

CREDIT: WIDANA ARACHCHIGE ERANDANI LAKSHANI

Tropical cyclone (TCs) are one of the most destructive types of weather event on Earth, damaging people’s lives and their property, local infrastructure, and subsequently causing enormous economic losses. TCs are strong circular storms originating in the warm tropical oceans and are accompanied by heavy rainfall and strong winds. However, there has been no consensus amongst scientists regarding the global-scale trends of TC frequency and intensity due to climate change effects on ocean temperatures. Hence, to achieve this, and ultimately be better prepared for these extreme weather events in the future, a holistic evaluation of the different TC characteristics across ocean basins is vital.

In a recent study published in Atmospheric and Oceanic Science Letters, Professor Wen Zhou from Fudan University, China, and Erandani Lakshani, a post-graduate researcher at the City University of Hong Kong, have shed more light on the observed decadal-scale shifts and trends in global TC activities from 1980 to 2021.

 The study reveals that there has been a significant increase in the number of TCs in the North Atlantic basin and North Indian Ocean over the past four decades, while there has been a decrease in the western North Pacific. It was also found that the genesis of TCs in the East Pacific, southern Indian Ocean, and South Pacific Ocean basins has declined since 1980, albeit this trend is not statistically significant.

Along with the frequency of TC genesis, the intensity of TCs has also varied significantly amongst the different ocean basins. “Notably, the average maximum TC intensity over the North Indian Ocean has increased recently, and this can be explained by an upward trend in mid-tropospheric relative humidity and decreasing vertical wind shear in the this basin”, outlines Professor Zhou and Lakshani. Their study also points out that the average TC intensity in the East Pacific has decreased dramatically, whereas over the South Pacific it has increased significantly.

Moreover, they observed an increasing TC intensity trend in the western North Pacific but a decreasing trend over the North Atlantic. The TC intensity in the North Atlantic may be linked to the decreasing trend in mid-tropospheric relative humidity, mainly south of the North Atlantic.

Another finding of this work is the indication of a significant association between the average large-scale characteristics of both vertical wind shear and relative humidity and the TC frequency in the different ocean basins. Moreover, the interdependence of TC frequency, vertical wind shear and relative humidity varies across the basins, indicating an inter-basin teleconnection (a term used in the atmospheric sciences to describe climate links between geographically separated regions).

In summary, this study provides valuable insights into global TC trends, which is critical towards improving our understanding of the evolution of TCs. Moreover, the study highlights the need for continued research into the underlying causes of these shifts in TC activity for future predictability and preparedness.

JOURNAL

Atmospheric and Oceanic Science Letters

DOI

10.1016/j.aosl.2022.100321 

ARTICLE TITLE

Observed decadal shifts and trends in global tropical cyclone activities from 1980 to 2021

Researchers find new approach to explore earliest universe dynamics with gravitational waves

Peer-Reviewed Publication

KAVLI INSTITUTE FOR THE PHYSICS AND MATHEMATICS OF THE UNIVERSE

 

IMAGE: SCHEMATIC OF THE INFLATON FIELD FRAGMENTED INTO OSCILLONS, WITH SUPERIMPOSED GRAVITATIONAL WAVES. view more 

CREDIT: KAVLI IPMU, VOLODYMYR TAKHISTOV

Researchers have discovered a new generic production mechanism of gravitational waves generated by a phenomenon known as oscillons, which can originate in many cosmological theories from the fragmentation into solitonic “lumps” of the inflaton field that drove the early Universe’s rapid expansion, reports a new study published in Physical Review Letters. 

The results have set the stage for revealing exciting novel insights about the Universe's earliest moments. 

The inflationary period, which occurred just after the Big Bang, is believed to have caused the Universe to expand exponentially. In many cosmological theories, the rapid expansion period is followed by the formation of oscillons. Oscillons are a type of localized non-linear massive structure that can form from fields, such as the inflaton field, which are oscillating at high frequencies. These structures can persist for long periods, and as the researchers found, their eventual decay can generate a significant amount of gravitational waves, which are ripples in space-time.  

In their study, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) Project Researcher Kaloian D. Lozanov, and Kavli IPMU Visiting Associate Scientist, International Center for Quantum-field Measurement Systems for Studies of the Universe and Particles (QUP) Senior Scientist, and High Energy Accelerator Research Organization (KEK) Theory Center Assistant Professor Volodymyr Takhistov, simulated the evolution of the inflaton field during the early Universe and found that oscillons were indeed present. They then found that oscillon decay was able to generate gravitational waves that would be detectable by upcoming gravitational wave observatories.

The findings provide a novel test of the early Universe dynamics independent of the conventionally studied cosmic microwave background radiation. The discovery of these gravitational waves would establish a new window into the Universe's earliest moments, and could help shed light on some of the pressing fundamental questions in cosmology.

With the ongoing development of gravitational wave detectors and supercomputing resources, we can expect to gain even more insights into the Universe's early moments in the coming years. Overall, the new study demonstrates the power of combining theoretical models with advanced computational techniques and observations to uncover new insights into the Universe's evolution.

Details of their study were published in Physical Review Letters on May 2.

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JOURNAL

Physical Review Letters

DOI

10.1103/PhysRevLett.130.181002 

ARTICLE TITLE

Enhanced gravitational waves from inflaton oscillons

Hidden supermassive black holes brought to life by galaxies on collision course

Peer-Reviewed Publication

ROYAL ASTRONOMICAL SOCIETY

 

IMAGE: AN ARTIST’S IMPRESSION OF A DUSTY REGION AROUND A BLACK HOLE. THE MOST DUST-ENSHROUDED BLACK HOLES CAN COMPLETELY STOP X-RAYS AND VISIBLE LIGHT ESCAPING, BUT THE SAME DUST CAN BE HEATED BY A GROWING BLACK HOLE AND WILL GLOW BRIGHTLY AT INFRARED WAVELENGTHS. view more 

CREDIT: ESA/NASA, THE AVO PROJECT AND PAOLO PADOVANI

Astronomers have found that supermassive black holes obscured by dust are more likely to grow and release tremendous amounts of energy when they are inside galaxies that are expected to collide with a neighbouring galaxy. The new work, led by researchers from Newcastle University, is published in Monthly Notices of the Royal Astronomical Society.

Galaxies, including our own Milky Way, contain supermassive black holes at their centres. They have masses equivalent to millions, or even billions, times that of our Sun. These black holes grow by ‘eating’ gas that falls on to them. However, what drives the gas close enough to the black holes for this to happen is an ongoing mystery.

One possibility is that when galaxies are close enough together, they are likely to be gravitationally pulled towards each other and ‘merge’ into one larger galaxy.

In the final stages of its journey into a black hole, gas lights up and produces a huge amount of energy. This energy is typically detected using visible light or X-rays. However, the astronomers conducting this study were only able to detect the growing black holes using infrared light. The team made use of data from many different telescopes, including the Hubble Space Telescope and infrared Spitzer Space Telescope.

The researchers developed a new technique to determine how likely it is that two galaxies are very close together and are expected to collide in the future. They applied this new method to hundreds of thousands of galaxies in the distant universe (looking at galaxies formed 2 to 6 billion years after the Big Bang) in an attempt to better understand the so-called ‘cosmic noon’, a time when most of the Universe’s galaxy and black hole growth is expected to have taken place.

Understanding how black holes grew during this time is fundamental in modern day galactic research, especially as it may give us an insight into the supermassive black hole situated inside the Milky Way, and how our galaxy evolved over time.

As they are so far away, only a small number of cosmic noon galaxies meet the required criteria to get precise measurements of their distances. This makes it very difficult to know with high precision if any two galaxies are very close to each other.

This study presents a new statistical method to overcome the previous limitations of measuring accurate distances of galaxies and supermassive black holes at cosmic noon. It applies a statistical approach to determine galaxy distances using images at different wavelengths and removes the need for spectroscopic distance measurements for individual galaxies.

Data arriving from the James Webb Space Telescope over the coming years is expected to revolutionise studies in the infrared and reveal even more secrets about how these dusty black holes grow.

Sean Dougherty, postgraduate student at Newcastle University and lead author of the paper, says, “Our novel approach looks at hundreds of thousands of distant galaxies with a statistical approach and asks how likely any two galaxies are to be close together and so likely to be on a collision course.”

Dr Chris Harrison, co-author of the study, “These supermassive black holes are very challenging to find because the X-ray light, which astronomers have typically used to find these growing black holes, is blocked, and not detected by our telescopes. But these same black holes can be found using infrared light, which is produced by the hot dust surrounding them.”

He adds, “The difficulty in finding these black holes and in establishing precise distance measurements explains why this result has previously been challenging to pin down these distant ‘cosmic noon’ galaxies. With JWST we are expecting to find many more of these hidden growing black holes. JWST will be far better at finding them, therefore we will have many more to study, including ones that are the most difficult to find. From there, we can do more to understand the dust that surrounds them, and find out how many are hidden in distant galaxies.”

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JOURNAL

Monthly Notices of the Royal Astronomical Society

ESO telescope reveals hidden views of vast stellar nurseries

Peer-Reviewed Publication

ESO

 

IMAGE: THIS IMAGE SHOWS THE L1688 REGION IN THE OPHIUCHUS CONSTELLATION. NEW STARS ARE BORN IN THE COLOURFUL CLOUDS OF GAS AND DUST SEEN HERE. THE INFRARED OBSERVATIONS UNDERLYING THIS IMAGE REVEAL NEW DETAILS IN THE STAR-FORMING REGIONS THAT ARE USUALLY OBSCURED BY THE CLOUDS OF DUST. THE IMAGE WAS PRODUCED WITH DATA COLLECTED BY THE VIRCAM INSTRUMENT, WHICH IS ATTACHED TO THE VISTA TELESCOPE AT ESO’S PARANAL OBSERVATORY IN CHILE. THE OBSERVATIONS WERE DONE AS PART OF THE VISIONS SURVEY, WHICH WILL ALLOW ASTRONOMERS TO BETTER UNDERSTAND HOW STARS FORM IN THESE DUST-ENSHROUDED REGIONS. view more 

CREDIT: ESO/MEINGAST ET AL.

Using ESO’s Visible and Infrared Survey Telescope for Astronomy (VISTA), astronomers have created a vast infrared atlas of five nearby stellar nurseries by piecing together more than one million images. These large mosaics reveal young stars in the making, embedded in thick clouds of dust. Thanks to these observations, astronomers have a unique tool with which to decipher the complex puzzle of stellar birth.

“In these images we can detect even the faintest sources of light, like stars far less massive than the Sun, revealing objects that no one has ever seen before,” says Stefan Meingast, an astronomer at the University of Vienna in Austria and lead author of the new study published today in Astronomy & Astrophysics. “This will allow us to understand the processes that transform gas and dust into stars.”

Stars form when clouds of gas and dust collapse under their own gravity, but the details of how this happens are not fully understood. How many stars are born out of a cloud? How massive are they? How many stars will also have planets?

To answer these questions, Meingast’s team surveyed five nearby star-forming regions with the VISTA telescope at ESO’s Paranal Observatory in Chile. Using VISTA’s infrared camera VIRCAM, the team captured light coming from deep inside the clouds of dust. “The dust obscures these young stars from our view, making them virtually invisible to our eyes. Only at infrared wavelengths can we look deep into these clouds, studying the stars in the making,” explains Alena Rottensteiner, a PhD student also at the University of Vienna and co-author of the study.

The survey, called VISIONS, observed star-forming regions in the constellations of Orion, Ophiuchus, Chamaeleon, Corona Australis and Lupus. These regions are less than 1500 light-years away and so large that they span a huge area in the sky. The diameter of VIRCAM’s field of view is as wide as three full Moons, which makes it uniquely suited to map these immensely big regions.

The team obtained more than one million images over a period of five years. The individual images were then pieced together into the large mosaics released here, revealing vast cosmic landscapes. These detailed panoramas feature dark patches of dust, glowing clouds, newly-born stars and the distant background stars of the Milky Way.

Since the same areas were observed repeatedly, the VISIONS data will also allow astronomers to study how young stars move. “With VISIONS we monitor these baby stars over several years, allowing us to measure their motion and learn how they leave their parent clouds,” explains João Alves, an astronomer at the University of Vienna and Principal Investigator of VISIONS. This is not an easy feat, as the apparent shift of these stars as seen from Earth is as small as the width of a human hair seen from 10 kilometres away. These measurements of stellar motions complement those obtained by the European Space Agency’s Gaia mission at visible wavelengths, where young stars are hidden by thick veils of dust.

The VISIONS atlas will keep astronomers busy for years to come. “There is tremendous long-lasting value for the astronomical community here, which is why ESO steers Public Surveys like VISIONS,” says Monika Petr-Gotzens, an astronomer at ESO in Garching, Germany, and co-author of this study. Moreover, VISIONS will set the groundwork for future observations with other telescopes such as ESO’s Extremely Large Telescope (ELT), currently under construction in Chile and set to start operating later this decade. “The ELT will allow us to zoom into specific regions with unprecedented detail, giving us a never-seen-before close-up view of individual stars that are currently forming there,” concludes Meingast.

More information

This research was presented in the paper “VISIONS: The VISTA Star Formation Atlas”, to appear in Astronomy & Astrophysics (doi: 10.1051/0004-6361/202245771)

The team is composed of Stefan Meingast (University of Vienna, Austria [Vienna]), João Alves (Vienna), Hervé Bouy (Université de Bordeaux, France [Bordeaux]), Monika G. Petr-Gotzens (European Southern Observatory, Germany [ESO]), Verena Fürnkranz (Max-Planck-Institut für Astronomie, Germany [MPIA]]), Josefa E. Großschedl (Vienna), David Hernandez (Vienna), Alena Rottensteiner (Vienna), Joana Ascenso (Universidade do Porto, Portugal [Porto]; Universidade de Lisboa, Portugal [Lisboa]), Amelia Bayo (ESO; Universidad de Valparaíso, Chile), Erik Brändli (Vienna), Anthony G. A. Brown (Leiden University, Netherlands), Jan Forbrich (University of Hertfordshire, UK [Hertfordshire]), Alyssa Goodman (Harvard-Smithsonian Center for Astrophysics, USA [CfA]), Alvaro Hacar (Vienna), Birgit Hasenberger (Vienna), Rainer Köhler (The CHARA Array of Georgia State University, USA), Karolina Kubiak (Lisboa), Michael Kuhn (Hertfordshire), Charles Lada (CfA), Kieran Leschinski (Vienna), Marco Lombardi (Università degli Studi di Milano, Italy), Diego Mardones (Universidad de Chile, Chile), Núria Miret-Roig (European Space Agency, European Space Research and Technology Centre, Netherlands [ESA]), André Moitinho (Lisboa), Koraljka Mužiiić (Porto; Lisboa), Martin Piecka (Vienna), Laura Posch (Vienna), Timo Prusti (ESA), Karla Peña Ramírez (Universidad de Antofagasta, Chile), Ronny Ramlau (Johannes Kepler University Linz, Austria; Johann Radon Institute for Computational and Applied Mathematics, Austria), Sebastian Ratzenböck (Vienna; Research Network Data Science at Uni Vienna), Germano Sacco (INAF – Osservatorio Astrofisico di Arcetri, Italy), Cameren Swiggum (Vienna), Paula Stella Teixeira (University of St Andrews, UK), Vanessa Urban (Vienna), Eleonora Zari (MPIA), and Catherine Zucker (Bordeaux).

The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration in astronomy. Established as an intergovernmental organisation in 1962, today ESO is supported by 16 Member States (Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom), along with the host state of Chile and with Australia as a Strategic Partner. ESO’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvellous place with unique conditions to observe the sky, hosts our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its Very Large Telescope Interferometer, as well as survey telescopes such as VISTA. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. Together with international partners, ESO operates ALMA on Chajnantor, a facility that observes the skies in the millimetre and submillimetre range. At Cerro Armazones, near Paranal, we are building “the world’s biggest eye on the sky” — ESO’s Extremely Large Telescope. From our offices in Santiago, Chile we support our operations in the country and engage with Chilean partners and society. 

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DOI

10.1051/0004-6361/202245771 

Astronomers reveal the largest cosmic explosion ever seen

Peer-Reviewed Publication

UNIVERSITY OF SOUTHAMPTON

 

IMAGE: ARTIST IMPRESSION OF A BLACK HOLE ACCRETION view more 

CREDIT: CREDIT JOHN A. PAICE WWW.JOHNAPAICE.COM/

A team of astronomers led by the University of Southampton have uncovered the largest cosmic explosion ever witnessed.

The explosion is more than ten times brighter than any known supernova (exploding star) and three times brighter than the brightest tidal disruption event, where a star falls into a supermassive black hole.

The explosion, known as AT2021lwx, has currently lasted over three years, compared to most supernovae which are only visibly bright for a few months. It took place nearly 8 billion light years away, when the universe was around 6 billion years old, and is still being detected by a network of telescopes.

The researchers believe that the explosion is a result of a vast cloud of gas, possibly thousands of times larger than our sun, that has been violently disrupted by a supermassive black hole. Fragments of the cloud would be swallowed up, sending shockwaves through its remnants, as well as into a large dusty ‘doughnut’ surrounding the black hole. Such events are very rare and nothing on this scale has been witnessed before.

Last year, astronomers witnessed the brightest explosion on record - a gamma-ray burst known as GRB 221009A. While this was brighter than AT2021lwx, it lasted for just a fraction of the time, meaning the overall energy released by the AT2021lwx explosion is far greater.

The findings of the research have been published today [Friday, 12 May 2023] in Monthly Notices of the Royal Astronomical Society.

Discovery

AT2021lwx was first detected in 2020 by the Zwicky Transient Facility in California, and subsequently picked up by the Asteroid Terrestrial-impact Last Alert System (ATLAS) based in Hawaii. These facilities survey the night sky to detect transient objects that rapidly change in brightness indicating cosmic events such as supernovae, as well as finding asteroids and comets. Until now the scale of the explosion has been unknown.

“We came upon this by chance, as it was flagged by our search algorithm when we were searching for a type of supernova,” says Dr Philip Wiseman, Research Fellow at the University of Southampton, who led the research. “Most supernovae and tidal disruption events only last for a couple of months before fading away. For something to be bright for two plus years was immediately very unusual.”

The team investigated the object further with several different telescopes: the Neil Gehrels Swift Telescope (a collaboration between NASA, the UK and Italy), the New Technology Telescope (operated by the European Southern Observatory) in Chile, and the Gran Telescopio Canarias in La Palma, Spain.

Measuring the explosion

By analysing the spectrum of the light, splitting it up into different wavelengths and measuring the different absorption and emission features of the spectrum, the team were able to measure the distance to the object.

“Once you know the distance to the object and how bright it appears to us, you can calculate the brightness of the object at its source. Once we’d performed those calculations, we realised this is extremely bright,” says Professor Sebastian Hönig from the University of Southampton, a co-author of the research.

The only things in the universe that are as bright as AT2021lwx are quasars - supermassive black holes with a constant flow of gas falling onto them at high velocity.

Professor Mark Sullivan, also of the University of Southampton and another co-author of the paper, explains: “With a quasar, we see the brightness flickering up and down over time. But looking back over a decade there was no detection of AT2021lwx, then suddenly it appears with the brightness of the brightest things in the universe, which is unprecedented.”

What caused the explosion?

There are different theories as to what could have caused such an explosion, but the Southampton-led team believe the most feasible explanation is an extremely large cloud of gas (mostly hydrogen) or dust that has come off course from its orbit around the black hole and been sent flying in.

The team are now setting out to collect more data on the explosion - measuring different wavelengths, including X-rays which could reveal the object’s surface and temperature, and what underlying processes are taking place. They will also carry out upgraded computational simulations to test if these match their theory of what caused the explosion.

Dr Philip Wiseman added: “With new facilities, like the Vera Rubin Observatory’s Legacy Survey of Space and Time, coming online in the next few years, we are hoping to discover more events like this and learn more about them. It could be that these events, although extremely rare, are so energetic that they are key processes to how the centres of galaxies change over time.”

Multiwavelength observations of the extraordinary accretion event AT2021lwx is published in Monthly Notices of the Royal Astronomical Society and is available to read online.

Ends

Notes for editors

1. Multiwavelength observations of the extraordinary accretion event AT2021lwx will be published in Monthly Notices of the Royal Astronomical Society at 00:01 GMT on Friday 12 May 2023.
2. A preprint of the paper is available to read at: https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stad1000/7115325
3. For further information and interviews with the following, please contact: Steve Williams, Media Relations, University of Southampton. press@soton.ac.uk 023 8059 3212:
   • Dr Philip Wiseman, University of Southampton
   • Professor Sebastian Hönig, University of Southampton
   • Professor Mark Sullivan, University of Southampton
   • Associate Professor Manda Banerji, University of Southampton
   • Associate Professor Matthew Middleton, University of Southampton
4. Images
   1. Artist impression of a black hole accretion. Credit John A. Paice.
   2. Images of the Zwicky Transient Facility. Credit Caltech
   3. Images of the New Technology Telescope. Credit European Southern Observatory
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JOURNAL

Monthly Notices of the Royal Astronomical Society

DOI

10.1093/mnras/stad1000 

ARTICLE TITLE

Multiwavelength observations of the extraordinary accretion event AT2021lwx

ARTICLE PUBLICATION DATE

12-May-2023

Portugal participates in the development of a first-class instrument for the largest telescope in the world

Reports and Proceedings

FACULTY OF SCIENCES OF THE UNIVERSITY OF LISBON

 

IMAGE: THIS ARTIST’S RENDERING SHOWS THE EXTREMELY LARGE TELESCOPE IN OPERATION ON CERRO ARMAZONES IN NORTHERN CHILE. THE TELESCOPE IS SHOWN USING LASERS TO CREATE ARTIFICIAL STARS HIGH IN THE ATMOSPHERE. THE FIRST STONE CEREMONY FOR THE TELESCOPE WAS ATTENDED BY THE PRESIDENT OF CHILE, MICHELLE BACHELET JERIA, ON 26 MAY 2017. view more 

CREDIT: ESO/L. CALÇADA

A research team from the University of Lisbon and University of Oporto (Portugal) participate in the development of METIS (Mid-infrared ELT Imager and Spectrograph). This powerful instrument will equip the largest telescope in the world - the Extremely Large Telescope (ELT) - under construction by the European Southern Observatory (ESO) in Armazones, Chile.

At this critical acceptance stage of the complete and final METIS design, ESO is presenting an illustrative film demonstrating the exceptional capabilities of the instrument. The presentation will take place on May 12, at 4:00pm (CEST).

METIS will detect radiation that is invisible to the human eye, that is, radiation that is “felt” in the form of “heat”. The instrument will take advantage of the ELT's giant primary mirror, measuring around 39 meters, to study a myriad of scientific topics, from objects in our solar system to distant active galaxies with revolutionary precision.

“This is one of the ELT's most complex instruments and the participation of the Portuguese team is proof of national capabilities in the development of large international projects. Involvement in this project not only allows them to apply their experience, but also to increase it, given the inherent challenges. It also allows Portugal to be at the forefront at the time of observations, and, in addition, promotes the participation of industry, involving the ecosystem as a whole”, says Marta Gonçalves, manager of Science and Education projects at the Portuguese Space Agency.

“Participating in the development of METIS has been a huge challenge, which has put our capacities for innovation, simulation, and construction of instruments for Astrophysics to the test. Projects like this also help to develop and promote the participation of Portuguese industry in major international projects. They strategically position us at the forefront as teachers, researchers, engineers and students”, says António Amorim, responsible for the Portuguese participation in METIS, Professor in the Physics Department of the Faculty of Sciences of the University of Lisbon (Ciências ULisboa) and member of CENTRA – Center for Astrophysics and Gravitation.

The Portuguese participation in the development of METIS has several fronts. The main contribution is the construction of the mechanical support structure, alignment and access to the instrument called Warm Support Structure (WSS). Portugal also contributes to the METIS operations team and also to the scientific team.

The total cost of the METIS instrument is around €95 million, and its mass is around 12 tons (equivalent to a double-decker bus). For Mercedes Filho, manager of METIS project in Portugal and researcher at the Physical Engineering Department at the Faculty of Engineering of University of Oporto (FEUP), “the WSS has extreme requirements. On the one hand, the WSS must position the instrument with an accuracy of 10 millionths of a rotation and 100 millionths of a meter. On the other hand, the WSS must withstand a major earthquake in complete safety, being able to support an equivalent mass of 40 tons!”.

The METIS project also involved the participation of PhD and Master's students, namely André Bone and Ricardo Costa, the former a PhD student in Physical Engineering at Ciências ULisboa and the latter a Master’s student in Mechanical Engineering at FEUP.

As for Astrophysics, many scientific discoveries are being prepared in detail given the extremely high cost and competition for infrastructure, as explained by Paulo Garcia, co-responsible for the Portuguese participation in METIS, researcher at CENTRA, and professor at the Department of Physical Engineering (DEF) at FEUP: “Portugal will have privileged access to METIS, to carry out observations of celestial phenomena with a top scientific instrument that transports us to the future of astrophysics. METIS will allow an unprecedented study of several astrophysical topics, and our priority at CENTRA is to study gravity in the vicinity of the supermassive black hole at the center of our galaxy. In particular, we intend to detect new stars in orbits closer to the black hole than currently known and study their motion.”

Other Portuguese researchers involved in the scientific preparation of this initiative are André Moitinho, Professor at Ciências Ulisboa, Koraljka Muzic, researcher at FEUP, and Alexandre Correia, professor at the Physics Department at the University of Coimbra.

The ELT is under construction in Armazones, Chile by ESO. The ELT will be the largest terrestrial optical and infrared telescope when it begins operations, scheduled for the middle of this decade. With its 39-meter diameter primary mirror and advanced adaptive optics systems, the telescope will be able to see details six times finer than the James Webb Space Telescope and 20 times finer than the Hubble Telescope.

  

METIS will be one of the detection instruments placed on the ELT platform.

CREDIT

ESO/METIS Consortium / L. Calçada

METIS International Consortium

The METIS consortium is made up of NOVA (Netherlands Research School for Astronomy, represented by Leiden University, The Netherlands), UK Astronomy Technology Center (UKATC, and Edinburgh, Scotland, UK), Max Planck Institute for Astronomy (MPIA, based in Heidelberg, Germany), Katholieke Universiteie Leuven (Belgium), Saclay Nuclear Research Center (CEA Saclay, France), ETH Zürich (Switzerland), A* (an Austrian partnership represented by the University of Vienna, the University of Innsbruck, the University of Graz , University of Linz, and RICAM Linz, Austrian Academy of Sciences, Austria), Universitat zu Koln (Germany), Ciências Ulisboa and FEUP, represented by CENTRA (Portugal), University of Liège (Belgium), Academia Sinica Institute of Astronomy and Astrophysics in Taipei (Taiwan) and the University of Michigan at Ann Arbor (USA), and, with contributions from ESO.

 

Schedule (CEST)

4:00pm ELT trailer starts: https://cdn.eso.org/videos/hd_1080p25_screen/elt-teaser-2021.mp4
4:01pm Welcome given by Suzanna Randal
4:05pm Short talk about the ELT by Michele Cirasuolo
4:10pm Suzanna Randal introduces METIS
4:11pm The METIS movie
4:21pm Q&A Session

 

Links
YouTube: https://www.youtube.com/watch?v=zgHFdokFyLU
Facebook messages and event: https://www.facebook.com/ESOAstronomy/posts/pfbid0kahjP5PJVNa3fTrzuanVJscYBANRE4LUbGRdWaG7smSFbBpyqtSLJheXJP7jyD23l 
Twitter: https://twitter.com/ESO/status/1653422689690832902
Linkedin: https://www.linkedin.com/feed/update/urn:li:activity:7059189856576380928