Bees evolved from ancient supercontinent, diversified faster than suspected

Peer-Reviewed Publication

WASHINGTON STATE UNIVERSITY

 

IMAGE: PHOTOS OF BEES MADE USING THE TEAM’S IMAGING SYSTEM. view more 

CREDIT: SILAS BOSSERT LAB/WSU

The first bees evolved on an ancient supercontinent more than 120 million years ago, diversifying faster and spreading wider than previously suspected, a new study shows.

Led by Washington State University researchers, the study provides a new best estimate for when and where bees first evolved. Newly published in the journal Current Biology, the project reconstructed the evolutionary history of bees, estimated their antiquity, and identified their likely geographical expansion around the world.

The results indicate their point of origin was in western Gondwana, an ancient supercontinent that at that time included today's continents of Africa and South America.

“There’s been a longstanding puzzle about the spatial origin of bees,” said Silas Bossert, assistant professor with WSU’s Department of Entomology, who co-led the project with Eduardo Almeida, associate professor at the University of São Paulo, Brazil.

Working with a global team, Bossert and Almeida’s team sequenced and compared genes from more than 200 bee species. They compared them with traits from 185 different bee fossils, as well as extinct species, developing an evolutionary history and genealogical models for historical bee distribution. In what may be the broadest genomic study of bees to date, they analyzed hundreds to thousands of genes at a time to make sure that the relationships they inferred were correct.

"This is the first time we have broad genome-scale data for all seven bee families,” said co-author Elizabeth Murray, a WSU assistant professor of entomology.

Previous research established that the first bees likely evolved from wasps, transitioning from predators to collectors of nectar and pollen. This study shows they arose in arid regions of western Gondwana during the early Cretaceous period.

"For the first time, we have statistical evidence that bees originated on Gondwana," Bossert said. "We now know that bees are originally southern hemisphere insects."

The researchers found evidence that as the new continents formed, bees moved north, diversifying and spreading in a parallel partnership with angiosperms, the flowering plants. Later, they colonized India and Australia. All major families of bees appeared to split off prior to the dawn of the Tertiary period, 65 million years ago—the era when dinosaurs became extinct.

The tropical regions of the western hemisphere have an exceptionally rich flora, and that diversity may be due to their longtime association with bees, authors noted. One quarter of all flowering plants belong to the large and diverse rose family, which make up a significant share of the tropical and temperate host plants for bees.

Bossert’s team plans to continue their efforts, sequencing and studying the genetics and history of more species of bees. Their findings are a useful first step in revealing how bees and flowering plants evolved together. Understanding how bees spread and filled their modern ecological niches could also help keep pollinator populations healthy.

“People are paying more attention to the conservation of bees and are trying to keep these species alive where they are,” Murray said. "This work opens the way for more studies on the historical and ecological stage.”

Additional contributors included Felipe Freitas, Washington State University; Bryan Danforth, Cornell University; Charles Davis, Harvard University; Bonnie Blaimer, Tamara Spasojevic, and Seán Brady, Smithsonian Institution; Patrícia Ströher and Marcio Pie, Federal University of Paraná, Brazil; Michael Orr, State Museum of Natural History, Stuttgart; Laurence Packer, York University; Michael Kuhlmann, University of Kiel; and Michael G. Branstetter, U.S. Department of Agriculture.

View the article in Current Biology.

 

Anthophora_californica

WASHINGTON STATE UNIVERSITY

Photo of bee made using the team’s imaging system.

CREDIT

Silas Bossert lab.

A piece of ancient amber containing a tiny, fossilized bee. Bossert and colleagues from around the globe compared features of bees from fossils, including extinct species, in one of the broadest genomic studies of bees to date.

CREDIT

Bossert lab.

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JOURNAL

Current Biology

DOI

10.1016/j.cub.2023.07.005 

ARTICLE TITLE

The evolutionary history of bees in time and space

ARTICLE PUBLICATION DATE

27-Jul-2023

 

600-million-year-old ocean water from Himalayas provides clues to Earth’s past

Peer-Reviewed Publication

INDIAN INSTITUTE OF SCIENCE (IISC)

 

IMAGE: TOP: FIELD EXPOSURES OF MAGNESITE NEAR CHANDAK HILLS, KUMAON. BOTTOM: MICROPHOTOGRAPHS OF OCEAN WATER TRAPPED IN MAGNESITE CRYSTALS view more 

CREDIT: PRAKASH CHANDRA ARYA

High up in the Himalayas, scientists at the Indian Institute of Science (IISc) and Niigata University, Japan, have discovered droplets of water trapped in mineral deposits that were likely left behind from an ancient ocean which existed around 600 million years ago. Analysis of the deposits, which had both calcium and magnesium carbonates, also allowed the team to provide a possible explanation for events that might have led to a major oxygenation event in Earth’s history. 

"We have found a time capsule for paleo oceans,” says Prakash Chandra Arya, PhD student at the Centre for Earth Sciences (CEaS), IISc, and first author of the study published in Precambrian Research. 

Scientists believe that between 700 and 500 million years ago, thick sheets of ice covered the Earth for an extended period, called the Snowball Earth glaciation (one of the major glacial events in Earth’s history). What followed this was an increase in the amount of oxygen in the Earth’s atmosphere, called the Second Great Oxygenation Event, which eventually led to the evolution of complex life forms. So far, scientists have not fully understood how these events were connected due to the lack of well-preserved fossils and the disappearance of all past oceans that existed in the Earth’s history. Exposures of such marine rocks in the Himalayas can provide some answers.  

“We don’t know much about past oceans,” says Prakash. “How different or similar were they compared to present-day oceans? Were they more acidic or basic, nutrient-rich or deficient, warm or cold, and what was their chemical and isotopic composition?” Such insights could also provide clues about the Earth’s past climate, and this information can be useful for climate modelling, he adds. 

The deposits found by the team – which date back to around the time of the Snowball Earth glaciation – showed that the sedimentary basins were deprived of calcium for an extended period, probably due to low riverine input. “During this time, there was no flow in the oceans, and hence no calcium input. When there is no flow or calcium input, as more calcium precipitates, the amount of magnesium goes up,” explains Sajeev Krishnan, Professor at CEaS and corresponding author of the study. The magnesium deposits formed at this time were able to trap paleo ocean water in their pore space as they crystallised, the researchers suggest. 

The calcium deprivation also likely led to a nutrient deficiency, making it conducive for slow-growing photosynthetic cyanobacteria, which could have started spewing out more oxygen into the atmosphere. “Whenever there is an increase in the oxygen level in the atmosphere, you will have biological radiation (evolution),” says Prakash.

The team hunted for these deposits across a long stretch of the western Kumaon Himalayas, extending from Amritpur to the Milam glacier, and Dehradun to the Gangotri glacier region. Using extensive laboratory analysis, they were able to confirm that the deposits are a product of precipitation from ancient ocean water, and not from other places, such as the Earth’s interior (for example, from submarine volcanic activity). 

The researchers believe that these deposits can provide information about ancient oceanic conditions such as pH, chemistry, and isotopic composition, which have so far only been theorised or modelled. Such information can help answer questions related to the evolution of oceans, and even life, in Earth’s history. 

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JOURNAL

Precambrian Research

DOI

10.1016/j.precamres.2023.107129 

ARTICLE TITLE

Himalayan magnesite records abrupt cyanobacterial growth that plausibly triggered the Neoproterozoic Oxygenation Event

 

How volcanic phosphorus supply boosted the Jehol Biota in northern China

Peer-Reviewed Publication

SCIENCE CHINA PRESS

 

IMAGE: MIDDLE–LATE MESOZOIC REGIONAL TECTONIC AND VOLCANIC RESPONSES IN NORTHERN CHINA TO SUBDUCTION OF THE PALEO-PACIFIC PLATE AND THE IMPACT OF VOLCANISM, SPECIFICALLY ON THE RAPID BLOOM OF THE YANLIAO AND JEHOL BIOTAS DUE TO SPIKES IN VOLCANIC P SUPPLY. FIGURE BY CHAO MA. view more 

CREDIT: ©SCIENCE CHINA PRESS

Have you ever heard of the Jehol Biota, a diverse assemblage of plants and animals during the Mesozoic Era that lived in what is now northern China? The Jehol Biota, which includes the earliest known flowering plants, feathered dinosaurs and early birds, had a high level of biodiversity and biomass compared to other contemporaneous Lagerstätten. But why was this area so rich in life during this period? Recent research suggests that the prosperity of this unique ecosystem was closely tied to the destruction of the North China Craton. The fascinating story of how the destruction of the craton led to the flourishing of the Jehol Biota has captivated scientists for years. A study conducted by a group of international researchers discovered a crucial factor that may have contributed to the flourishing of the Jehol Biota during a time of upheaval: volcanic phosphorus (P).

During the Mesozoic Era, the North China Craton underwent a period of destruction that caused massive volcanic eruptions, spewing ash and lava across the landscape. As the volcanic products weathered over time, they released large amounts of an essential nutrient for life known as P into the soil and water. This allowed plants to grow more quickly and become more abundant, which in turn supported a thriving ecosystem of animals, from insects to dinosaurs.

Lead author of the study, Professor Yanjie Tang of the Institute of Geology and Geophysics, Chinese Academy of Sciences, said: "Our research shows that the flourishing of the terrestrial biotas in northern China during the Mesozoic Era was not just due to a fortuitous combination of factors, but was in fact a response to the unique geological conditions of the time."

By analyzing the volcanic-sedimentary sequences in northern China, researchers have traced the changes in P delivery, biological productivity and species abundance over time. They have found that there were episodic increases in P supply, which coincided with periods of high biological productivity and species abundance. In addition, the younging trend of Jehol fossils is consistent with the migration of volcanism with increased volcanic P supply in northern China. These phenomena suggest that the elevated volcanic P supply from volcanic weathering to terrestrial ecosystems played a significant role in the Jehol Biota's success. The increased P supply was not a steady stream, however. Instead, it occurred in pulses, corresponding to the dynamics of Jehol Biota radiation.

Interestingly, this pattern of volcanic-biotic coupling was not unique to the Jehol Biota. Similar phenomena were observed in the preceding Yanliao Biota, which had relatively fewer fossils but still showed evidence of volcanic P supply. As the North China craton continued to be destroyed and volcanic activity increased, the supply of P grew, creating an environment more conducive to the high prosperity of the Jehol Biota.

Researchers are still working to understand the precise mechanisms involved in this process. One thing is clear, however: the Jehol and Yanliao biotas are a testament to the incredible complexity of life on Earth and the many factors that contribute to the evolution of different species. The biotas serve as a reminder of the incredible diversity and resilience of life, and how it can adapt and thrive even in the face of dramatic environmental changes. By studying the link between craton destruction and biota development, researchers are gaining a better understanding of the intricate relationships between geology, climate, and biology that have shaped our planet over millions of years.

See the article: 

Volcanic phosphorus supply boosted Mesozoic terrestrial biotas in northern China
https://doi.org/10.1016/j.scib.2023.05.022

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JOURNAL

Science Bulletin

DOI

10.1016/j.scib.2023.05.022 

 

Insolation affected ice age climate dynamics

Researchers from Germany, Austria, and Switzerland use stalagmites to document the significance of orbital insolation for abrupt changes in ice age climate

Peer-Reviewed Publication

HEIDELBERG UNIVERSITY

In past ice ages, the intensity of summer insolation affected the emergence of warm and cold periods and played an important role in triggering abrupt climate changes, a study by climate researchers, geoscientists, and environmental physicists suggests. Using stalagmites in the European Alps, they were able to demonstrate that warm phases appeared primarily when the summer insolation reached maxima in the Northern Hemisphere. Study participants included scientists from Germany, Austria, and Switzerland led by researchers from Heidelberg University and the GFZ German Research Centre for Geosciences Potsdam.

Past ice ages in the Northern Hemisphere were marked by sudden transitions between cold and warm phases, each lasting several thousand years. The reason for these fluctuations has yet to be resolved, but research does point to effects relating to the size of the continental ice sheets. Greenland ice records 25 such warm-cold cycles between 115,400 and 14,700 years ago. Investigating stalagmites in the Melchsee-Frutt cave system in the Swiss Alps, the researchers were able to investigate for the first time and with high precision 16 such fluctuations in the penultimate glacial period 185,000 to 130,000 years ago.

Stalagmites in caves are crucial archives in climate research and offer clues as to changes in temperature, precipitation, and vegetation cover. “We are able to precisely determine their age and hence analyse the chronological sequence of abrupt ice age climate fluctuations, which we identify using oxygen isotope values,” explains Prof. Dr Norbert Frank of the Institute of Environmental Physics at Heidelberg University. “Our investigations targeted whether, in addition to ice volumes in the Northern Hemisphere, orbitally driven changes in the global distribution of insolation could have influenced the abrupt changes in climate,” states study head Dr Jens Fohlmeister, who earned his doctorate in environmental physics at Heidelberg University and worked at the GFZ German Research Centre for Geosciences Potsdam and the Potsdam Institute for Climate Impact Research during the investigations.

The researchers studied the transitions of warm-cold cycles in the penultimate ice age by analysing the age and oxygen isotope composition of stalagmites from the Melchsee-Frutt cave system. “Based on the newly acquired data, we were able to show that warm phases occurred mainly during the peak phase of summer insolation in the Northern Hemisphere, even when the sea level, which is dependent on the volume of the continental ice sheets, remained close to its minimum during peak glacial periods,” explains Dr Fohlmeister. Model simulations confirmed these findings. In accordance with the research data from the cave system, the simulations predict the frequency as well as the duration of warm phases at the corresponding sea level and existing insolation.

Scientists from the Potsdam Institute for Climate Impact Research, the GFZ German Research Centre for Geosciences Potsdam, Heidelberg University, the University of Innsbruck (Austria), the Swiss Institute for Speleology and Karst Studies, and the Karst and Caves Natural Heritage Foundation Obwalden (Switzerland) participated in the study. The research was funded by the German Research Foundation. The results were published in the journal “Communications Earth & Environment”.

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JOURNAL

Communications Earth & Environment

DOI

10.1038/s43247-023-00908-0 

ARTICLE TITLE

The role of Northern Hemisphere summer insolation for millennial-scale climate variability during the penultimate glacial

 

New clues on the source of the universe’s magnetic fields

The source of magnetic fields has long been debated. New research offers clues on their origins.

Peer-Reviewed Publication

COLUMBIA UNIVERSITY

It isn’t just your refrigerator that has magnets on it. The earth, the stars, galaxies, and the space between galaxies are all magnetized, too. The more places scientists have looked for magnetic fields across the universe, the more they’ve found them. But the question of why that is the case and where those magnetic fields originate from has remained a mystery and a subject of ongoing scientific inquiry. 

A new paper by Columbia researchers offers insight into the source of these fields. The team used models to show that magnetic fields may spontaneously arise in turbulent plasma. Plasma is a kind of matter often found in ultra-hot environments like that near the surface of the sun, but plasma is also scattered across the universe in low-density environments, like the expansive space between galaxies; the team’s research focused on those low-density environments. Their simulations showed that, in addition to generating new magnetic fields, the turbulence of those plasmas can also amplify magnetic fields once they’ve been generated, which helps explain how magnetic fields that originate on small scales can sometimes eventually reach to stretch across vast distances.

The paper was written by astronomy professor Lorenzo Sironi, astronomy research scientist Luca Comisso, and astronomy doctoral candidate Ryan Golant. 

“This new research allows us to imagine the kinds of spaces where magnetic fields are born: even in the most pristine, vast, and remote spaces of our universe, roiling plasma particles in turbulent motion can spontaneously give birth to new magnetic fields,” Sironi said. “The search for the ‘seed’ that can sow a new magnetic field has been long, and we’re excited to bring new evidence of that original source, as well as data on how a magnetic field, once born, can grow.” 

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JOURNAL

Physical Review Letters

DOI

10.1103/PhysRevLett.131.055201 

METHOD OF RESEARCH

Computational simulation/modeling

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Generation of near-equipartition magnetic fields in turbulent collisionless plasmas

ARTICLE PUBLICATION DATE

31-Jul-2023

 

COSPAR to launch new space science education program

INTERNATIONAL SCIENCE COUNCIL COMMITTEE ON SPACE RESEARCH

The Committee on Space Research (COSPAR) is pleased to announce the launch of an ambitious series of space science education projects through its Panel on Education, starting with participation in an Erasmus+ programme.

COSPAR and the Erasmus+ Education Programme

COSPAR’s participation in an Erasmus+ programme on education is part of the COSPAR Panel on Education’s new approach to its mission of developing “means and media to encourage and spread space-related education”.  The recent successful proposal for this Erasmus+ programme on cooperation partnerships in school education, coordinated by the Austrian Space Forum (OeWF), marks the start of this new approach.

The EXpeditionary Program for Learning OppoRtunities in Analog Space Exploration (EXPLORE) is a 36-month project—starting 1 September 2023—to introduce a new trend of activities engaging students in space exploration experiences that meet the requirements of their STEAM (science, technology, engineering, arts and mathematics) curriculum. EXPLORE will invite students to engage in activities similar to existing analog missions that simulate Moon or Mars environments. Educators will receive training to deliver curriculum content and improve their knowledge of digital solutions, as well as student-centred, inclusive, equitable and accessible methodologies while implementing the project.

EXPLORE will produce a kit that will encourage students to embrace an exploratory mission to Mars. Educators will receive training and support to adapt this kit to the curricula and conduct classroom involvement in the preparation of the missions. A group of selected students will visit a planetary surface analog site where they will simulate an international space mission and collaborate with peers and professionals from participating countries.

Students will have the opportunity to learn about space exploration and its importance in our daily lives, understand the importance of preserving the Earth’s environment with hands-on experience, improve their digital skills, become problem solvers, learn to collaborate, and get acquainted with innovative digital solutions. Educators will be introduced to innovative student-centred methodologies that facilitate the integration of digital content into the STEAM curriculum.

EXPLORE will be coordinated by the Austrian Space Forum (OeWF), with the active participation of COSPAR, NUCLIO, Ellinogermaniki Agogi and BIOSKY, LDA.

At the heart of the COSPAR Panel on Education’s new initiatives is a move to enhance teacher training. Efforts to bring space research to educators and trainers will be stepped up, by expanding the teacher training programme during the biennial COSPAR Scientific Assembly, by including this opportunity in the COSPAR Symposia, held in alternate years to the Assembly, and by forming partnerships with organisations such as the International Astronomical Union (IAU) and the Global Hands-On Universe (G-HOU).

The COSPAR President, Professor Pascale Ehrenfreund said: “We are looking forward to including new activities within the COSPAR community that will address the Committee’s future sustainability, influence, and impact within the international space sector. It is my firm belief that focusing on the new generation of scientists and researchers, providing support, opportunities, and capacity building in space-developing countries is beneficial to all.”

The Executive Director of COSPAR, Dr Jean-Claude Worms, stated: “A generation of pioneering space researchers is retiring. COSPAR places great emphasis on enabling the next generation to reap the benefits of the heavy investments and efforts conducted in the space sector by a steadily growing number of actors, public and private.  It is vital that this opening new age of space exploration and astronomy is conducted in an ethical and sustainable manner, allowing both scientific exploration and use of celestial bodies. This approach also applies to Earth observation from space, a critical aspect of the fight against climate change.  Capacity Building of countries accessing the space field is crucial, as is the education and training of young researchers and teachers, in order to better address these issues, and inform the public and the decision-makers.”

Chair of COSPAR’s Panel on Education, Rosa Doran, said: “The next astronauts setting foot on the Moon or Mars are probably sitting in a classroom somewhere around the world. The space industry is blooming, and jobs related to this important field are become more and more relevant. COSPAR’s Panel on Education aims to bring this reality closer to the students’ learning experiences. EXPLORE will be the first of many new ideas and partnerships that will put COSPAR at the centre stage for Space Education.

 

Background

The COSPAR activity that is particularly relevant to this ERASMUS+ educational project is developed by the Panel on Education. The COSPAR Panel on Education, under the dynamic Chair Rosa Doran, aims to adopt a more active approach towards its growth and impact within COSPAR, to broaden its target audience from educators to a whole-school approach, involving all members of the schools and their local communities, to reach out to policy makers and to guarantee a deeper involvement of its members towards a common goal: generating greater awareness of the importance of space science and how it is already impacting society.

The Panel on Education works on the development of means and appropriate media for encouraging and spreading space-related education. The Panel meets during education-targeted sessions at Assemblies or other events and supports relevant educational initiatives or entities outside of Assemblies. It works with COSPAR Scientific Commission Chairs, Panels, and other interested parties to identify the audience to whom the outreach and education is aimed, whether primary and secondary schools, universities, the general public via journalistic media, students, and especially underprivileged students in countries where space-related activities do not exist.

The Panel seeks to identify how to make educational tools and media available, and it explores possible links to and interactions with already established educational programs on topics related to research areas covered by COSPAR. It seeks to identify funding opportunities within certain countries for education and outreach work, and sets up and maintains websites or other relevant communication tools. The Panel also establishes links and strategic partnerships and alliances, for example with UNESCO, so that its activities can be supported without unnecessary duplication. The four Officers in charge of this Panel, and the 

very large body of volunteers (both teachers and scientists) working to support its activities and events have extensive experience of developing international educational projects, including EU-funded programmes, in particular ERASMUS+.

 

Issued by                   COSPAR Communications, Ms Leigh FERGUS leigh.fergus@cosparhq.cnes.fr

                                     

Note to Editors

COSPAR, the Committee on Space Research, was created in 1958, at the dawn of the space age, under the aegis of the International Council of Scientific Unions, now the International Science Council (ISC). COSPAR’s objectives are to promote on an international level scientific research in space, with emphasis on the exchange of results, information and opinions, and to provide a forum, open to all scientists, for the discussion of problems affecting space research. In its first years of existence as an entity that ignores political considerations and views all questions solely from the scientific standpoint, COSPAR played an important role as an open bridge between East and West for cooperation in space. When this role became less prominent with the end of the Cold War, COSPAR focused its objectives on the progress of all kinds of research carried out with the use of space means.

COSPAR has played a central role in the development of new space disciplines such as life sciences and fundamental physics in space, by facilitating the interaction between scientists in emerging space fields and senior space researchers.

A recent emphasis is the development of tighter bonds between science and industry, through the establishment of the Committee on Industry Relations, grouping 18 major aerospace companies worldwide, and advising COSPAR on how best to integrate the capabilities of industry into COSPAR’s activities and by doing so, to best serve the interests of industry and science in a synergistic way.

COSPAR strives to promote the use of space science for the benefit of humanity and for its adoption by developing countries and new space-faring nations, in particular through a series of Capacity Building Workshops which teach very practical skills enabling researchers to participate in international space research programs.

COSPAR advises, as required, the United Nations and other intergovernmental organizations on space research matters and on the assessment of scientific issues in which space can play a role, for example the Group on Earth Observations (GEO), in which COSPAR is a Participating Organization.

Finally, COSPAR is the key entity worldwide in terms of developing, maintaining and promulgating clearly delineated policies and requirements as to the standards that must be achieved to protect against the harmful effects of biological interchange in the conduct of solar system exploration and use.

COSPAR web page

COSPAR LinkedIn page           COSPAR Facebook page

COSPAR Twitter account          COSPAR YouTube channel

 

About Erasmus+
Erasmus+ is the EU's programme to support education, training, youth and sport in Europe. It has an estimated budget of €26.2 billion. This is nearly double the 

funding compared to its predecessor programme (2014-2020). The 2021-2027 programme places a strong focus on social inclusion, the green and digital transitions, and promoting young people’s participation in democratic life. It supports priorities and activities set out in the European Education Area, Digital Education Action Plan and the European Skills Agenda. The programme also supports the European Pillar of Social Rights; implements the EU Youth Strategy 2019-2027; and develops the European dimension in sport.

Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Education and Culture Executive Agency (EACEA). Neither the European Union nor EACEA can be held responsible for them.

 

About the Austrian Space Forum (OeWF)
The Austrian Space Forum is one of the world’s leading institutions conducting Mars analog missions, thus paving the way for the future human exploration of the Red Planet. Experts from a broad variety of disciplines as well as the spaceflight sector constitute the core of the OeWF’s continued endeavours that on a regular basis include national and international institutions from science and industry to work at the cutting edge of scientific research. In doing so the Austrian Space Forum is using its excellent contacts to opinion leaders, politics and media to further and internationally propagate Austrian top-level research. The Austrian Space Forum also contributes significantly to inspiring and educating young people in the sectors of science, technology and engineering. The OeWF offers internships to students and pupils, its experts supervise scientific papers on a regular basis.
Media Contact:
Mag. Monika Fischer
OeWF Media Team Lead
monika.fischer@oewf.org       For more information, visit www.oewf.org

 The universal sound of black holes

Mysterious and inescapable: Black holes are some of the most exotic objects in the Universe. Researchers at HITS, Germany, predict that the chirp sound that two black holes produce when they merge preferentially occur in two universal frequency ranges

Peer-Reviewed Publication

HEIDELBERG INSTITUTE FOR THEORETICAL STUDIES (HITS)

 

IMAGE: RIPPLES IN THE SPACETIME AROUND A MERGING BINARY BLACK-HOLE SYSTEM FROM A NUMERICAL RELATIVITY SIMULATION. view more 

CREDIT: IMAGE CREDIT: DEBORAH FERGUSON, KARAN JANI, DEIRDRE SHOEMAKER, PABLO LAGUNA, GEORGIA TECH, MAYA COLLABORATION

The discovery of gravitational waves in 2015 – already postulated by Einstein one hundred years ago – led to the 2017 Nobel Prize in Physics and initiated the dawn of gravitational-wave astronomy. When two stellar-mass black holes merge, they emit gravitational waves of increasing frequency, the so-called chirp signal, that can be “heard” on Earth. From observing this frequency evolution (the chirp), scientists can infer the so-called “chirp mass”, a mathematical combination of the two individual black hole masses.

So far, it has been assumed that the merging black holes can have any mass. The team’s models, however, suggest that some black holes come in standard masses that then result in universal chirps. “The existence of universal chirp masses not only tells us how black holes form”, says Fabian Schneider, who led the study at HITS, “it can also be used to infer which stars explode in supernovae.” Apart from that it provides insights into the supernova mechanism, uncertain nuclear and stellar physics, and provides a new way for scientists to measure the accelerated cosmological expansion of the Universe.

“Severe consequences for the final fates of stars”

Stellar-mass black holes with masses of approximately 3-100 times our Sun are the endpoints of massive stars that do not explode in supernovae but collapse into black holes. The progenitors of black holes that lead to mergers are originally born in binary star systems and experience several episodes of mass exchange between the components: in particular, both black holes are from stars that have been stripped off their envelopes. “The envelope stripping has severe consequences for the final fates of stars. For example, it makes it easier for stars to explode in a supernova and it also leads to universal black hole masses as now predicted by our simulations”, says Philipp Podsiadlowski from Oxford University, second author of the study and currently Klaus Tschira Guest Professor at HITS.

The “stellar graveyard”  – a collection of all known masses of the neutron-star and black-hole remains of massive stars – is quickly growing thanks to the ever-increasing sensitivity of the gravitational-wave detectors and ongoing searches for such objects. In particular, there seems to be a gap in the distribution of the chirp masses of merging binary black holes, and evidence emerges for the existence of peaks at roughly 8 and 14 solar masses . These features correspond to the universal chirps predicted by the HITS team. “Any features in the distributions of black-hole and chirp masses can tell us a great deal about how these objects have formed”, says Eva Laplace, the study’s third author.

Not in our galaxy: Black holes with much larger masses

Ever since the first discovery of merging black holes, it became evident that there are black holes with much larger masses than the ones found in our Milky Way. This is a direct consequence of these black holes originating from stars born with a chemical composition different from that in our Milky Way Galaxy. The HITS team could now show that – regardless of the chemical composition – stars that become envelope-stripped in close binaries form black holes of <9 and >16 solar masses but almost none in between.

In merging black holes, the universal black-hole masses of approximately 9 and 16 solar masses logically imply universal chirp masses, i.e. universal sounds. “When updating my lecture on gravitational-wave astronomy, I realized that the gravitational-wave observatories had found first hints of an absence of chirp masses and an overabundance at exactly the universal masses predicted by our models”, says Fabian Schneider. “Because the number of observed black-hole mergers is still rather low, it is not clear yet whether this signal in the data is just a statistical fluke or not”.

Whatever the outcome of future gravitational-wave observations: the results will be exciting and help scientists understand better where the singing black holes in this ocean of voices come from.

Publication:
Fabian R. N. Schneider, Philipp Podsiadlowski, and Eva Laplace: Bimodal Black Hole Mass Distribution and Chirp Masses of Binary Black Hole Mergers. The Astrophysical Journal Letters, 950, 2, DOI 10.3847/2041-8213/acd77a, https://iopscience.iop.org/article/10.3847/2041-8213/acd77a

HITS press release (with videos and images): https://www.h-its.org/2023/07/31/set-black-holes-sound/

The project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 945806).

Chirp mass distribution (IMAGE)

HEIDELBERG INSTITUTE FOR THEORETICAL STUDIES (HITS)

Distribution of the chirp masses of all binary black-hole mergers observed today. The top panel shows the raw data and probability distributions of the chirp masses of each individual event while the bottom panel shows a model inferred from the combined observations. The gap in chirp masses at 10–12 solar masses and the so-far identified features at about 8, 14, 27 and 45 solar masses are indicated. Figure reproduced from Abbott et al. 2021.

CREDIT

Abbott et al, 2021. https://journals.aps.org/prx/abstract/10.1103/PhysRevX.11.021053

JOURNAL

The Astrophysical Journal Letters

DOI

10.3847/2041-8213/acd77a 

METHOD OF RESEARCH

Computational simulation/modeling

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Bimodal Black Hole Mass Distribution and Chirp Masses of Binary Black Hole Mergers