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Jean Salata is a climate optimist, enough to often elicit a gentle eyeroll from his wife, Melanie.

“I am very optimistic — and as I was joking last night — my wife would say that I’m delusional,” Salata said Wednesday.

Despite that optimism, Salata, CEO of one of Asia’s largest private equity firms, Baring Private Equity Asia, isn’t kidding himself about the complexities of the climate crisis. He knows it is a multifaceted, global issue that will affect the world his children and grandchildren inherit. But he decided that his best shot for making a real difference was to find a place with robust resources, deep talent, and the right leaders, and then just step back. And, he said, that is what he did.

“I’m optimistic that we can make a difference,” Salata said at the kickoff event of the new institute that bears his and Melanie’s name. “It’s not going to be easy. We’re not going to do it alone. We can galvanize all the resources that the University has to be a beacon to the rest of the world, almost like a call to action of why this is important and how we together are going to solve this problem.

Several speakers at Wednesday’s event, “The Future is Now: Harvard Takes on the Climate Challenge,” cited Harvard’s broad interdisciplinary breadth and leadership in higher education as reasons why it is imperative the University engage fully on the problem. They said the new Salata Institute for Climate and Sustainability will fill an important role in the array of research, teaching, and other activities related to climate change taking place on Harvard’s campuses. Indeed, a recent report commissioned by James Stock, Vice Provost for Climate and Sustainability, concluded that despite the abundance of climate change-related courses, events, research opportunities, internships, and other types of engagement already offered at the University there remains a huge desire for more.

The Salata Institute, which Stock will head, seeks to play a unifying, catalyzing role that ultimately brings a University-wide focus to a massive, complex, and existential dilemma that has at times driven researchers, scholars, and students nearly to the point of throwing up their hands in resignation.

Scientists know that dark matter exists because although we can’t see it, we can see the effects of what it does in the world, sort of like a ghost bumping around a haunted house. And we’re not sure what it is, but some think it may just be a WIMP.

Those are some of the insights that emerged from a Harvard Science Book Talk on Monday that featured an online conversation between Peter Fisher, the Thomas A. Frank Professor of Physics at MIT, who just wrote a book titled “What Is Dark Matter?,” and Melissa Franklin, Mallinckrodt Professor of Physics at Harvard.

Fisher opened the event, sponsored by the Harvard Division of Science, Harvard Library, and Harvard Book Store, with a short response to the question the title poses: “The answer is we don’t know.” He offered several possibilities, explaining that his subject could be a particle, a heavy particle, “tiny black holes from the beginning of the universe, or it could be something we haven’t even thought of.”

To shed some light on the topic, Fisher recounted the history of particle physics, from the invention of quantum mechanics in the 1930s to the development of the standard model theory in the 1990s, which explains three out of four known fundamental forces (electromagnetic, weak and strong interactions, but not gravity).

Parallel to the development of this science, astronomers studying the universe were making discoveries about the movement of the stars away from the Earth — proof the universe is expanding. That movement, astronomers realized, was happening faster than forces such as the gravity of the component stars could explain. “They studied the way galaxies moved with respect to each other, and the way stars moved within galaxies. And the only way they could come up with explaining how everything was moving in the biggest scales of the universe was the introduction of matter that we couldn’t see,” he said.

The answer, requiring all these disciplines, was that there “were actually two kinds of matter that we couldn’t see.” These were dark energy and dark matter. “Dark matter makes particles or stars within galaxies move more quickly than you’d expect from the mass in those galaxies,” he said.

To illustrate, Fisher shared a slide of the Andromeda galaxy, with its lush swirl of stars emanating out in a flat disc. “It looks very similar to the Milky Way in the middle,” he said, pointing out the “glowing region in the very middle of that: a big black hole about a million times the mass of our sun. There’s a lot of matter being pulled into the dense central region, and you can see there’s this beautiful pancake shape with spiral arms,” containing roughly a trillion stars.

“What’s particularly interesting is you can see that there’s a sharp end to the disc part. And that edge is really only explainable if you hypothesize that there is some substance called dark matter that is making a gravitational pull that makes that shape.”

Andromeda is not unique. In fact, Fisher explained, images of deep space provided by the Hubble Space Telescope reveal a striking consistency. “There have been very detailed measurements of literally thousands of galaxies, and they all share the same features,” he said. “A careful study of all these different kinds of galaxies always comes up with the same conclusion, which is the stars are moving too fast to be explainable by the amount of light coming from that galaxy,” he said. “This must denote the presence of dark matter around the galaxy.”

Franklin, paraphrasing Fisher’s book, likened the search to a ghost hunt. “If you have ghosts in your house moving things around, you can’t see them or hear them or feel them. So what you want to do is figure out from the movements what exactly is going on.”

What dark matter is, however, is much less clear. One theory is that it is a new kind of particle, a weakly interacting massive particle (or WIMP). If that theory is correct, said Fisher, dark matter is likely all around — but “here on Earth, it’s hard to find dark matter because there’s so much normal matter around. You have to look and think about galaxies as a whole” in order to get a large enough scale to study dark matter.

Another theory is that dark matter is primordial black holes, dating back to the origins of the universe. If that’s the case, Fisher noted, these “tiny” bits of matter “could just go straight through the Earth. They don’t pick up much matter. They can go straight through pretty much anything and nobody really notices it.”

The ongoing search, Fisher cautioned, will require continuing advancements in technology but also caution and a careful understanding of how our tools work. To illustrate what can go wrong, he described the nation’s Distant Early Warning Line, a system of radar stations along the Arctic Circle created as a defense against a possible Soviet missile attack during the Cold War. “These radar operators saw all kinds of stuff that it took years to explain,” he said, resulting in theories about UFOs that are still around. “Anytime you build a new device, you see things you don’t expect.”

As the search for dark matter continues, such meticulous discipline is vital. However, despite the many questions that remain, we can be confident that dark matter exists because “all of the measurements are made repeatedly using very different kinds of telescopes,” he said. The movement of stars, for example, has been observed with large optical telescopes and also radio telescopes. “It’s not a guarantee, but it gives one confidence that the same overall effect is observed in two very different ways.”

Climate change experts were by turns optimistic and pessimistic at the Harvard Radcliffe Institute on Friday. Even as the cost of renewable energy plummets, they said, the slow pace of progress threatens irreversible damage to the planet.

Existing commitments from international leaders would reduce 2010 emissions 7.5 percent by 2030, dramatically short of the 55 percent needed to limit warming to 1.5 degrees Celsius by 2100, a level that scientists believe would head off climate change’s most catastrophic effects. The number is also well short of the 30 percent reduction that would keep warming at 2 degrees above preindustrial levels, noted Lis Mullin Bernhardt, deputy head of the United Nations’ Environment Program and one of the speakers at the institute’s daylong Mike and Nina Patterson Science Symposium.

“We know we have to bend that curve extremely, extremely fast,” Bernhardt said. “We cannot give up on that quest, as daunting as it obviously is at the moment, because existing commitments will result in warming of 2.7 degrees by the end of the century.”

Bernhardt and other panelists pointed out that the effects of climate change are multiplying even with today’s 1.1 degree warming: stronger hurricanes, more intense wildfires and droughts, and longer and hotter heat waves. Even so, she described herself as “climate optimistic.” Such an attitude is necessary if the U.N. and other organizations are to convince world leaders to ramp up their efforts against climate change, she said.

“If we don’t believe in a better future for ourselves and our children, how are we going to get countries to go toward that vision?”

Jim Stock, Harvard’s vice provost for climate and sustainability, said that U.S. climate and energy policy has arrived at a “fascinating moment.” Prices for solar and wind energy have fallen to the point where the technologies are now viable options, which wasn’t true 15 years ago. With hundreds of billions of dollars available from the Inflation Reduction Act, Stock said that U.S. leaders should move to build out the clean energy grid and expand the nation’s electric vehicle fleet. They should also take steps to ensure that the transition doesn’t leave disadvantaged communities behind, he said.

Klaus Lackner, director of the Center for Negative Climate Emissions at Arizona State University, would like to see a renewables-like technological leap in carbon-removal efforts. We have the ability to remove carbon and sequester it underground, but the technology is too expensive to be deployed at scale. And scale is essential, he said. Carbon dioxide remains in the atmosphere for somewhere between 50,000 and 100,000 years, meaning that even if emissions dropped to zero tomorrow, the planet would absorb the effects of climate change for decades. He estimated that the world will need to remove upward of 40 gigatons of carbon annually.

“We really should start thinking of CO₂ as a waste-management problem,” Lackner said. “These technologies are a generation behind because nobody wanted them.”

As the summer’s heat waves and historic flooding in Pakistan have demonstrated, the climate burden falls heavily on poorer people in places that have had little to do with the industrialization driving the crisis. Debra Roberts, co-chair of the Intergovernmental Panel on Climate Change Working Group II, said that the world’s climate change calculus has to include the continued development of low- and middle-income nations. The focus should be on helping these countries use clean energy to power their growth, she said.

Moving forward, experts and government officials should heed lessons of the COVID crisis in shaping climate policy, according to James Marshall Shepherd, director of the Atmospheric Sciences Program at the University of Georgia. Shepherd said the pandemic holds both positive and negative lessons. On one hand, as with climate, both misinformation and inequality have been part of the COVID narrative. At the same time, nations have come together over the past three years to meet a global challenge.

“Operation Warp Speed was an effort to rapidly develop — for the sake of us all — vaccines. And that was a good thing,” Shepherd said. “We marshalled all of our resources to that problem and I have argued for years that the climate crisis is an international and a national emergency that warrants the scale of a Manhattan Project, of an Apollo Project, of a Panama Canal project, an Operation Warp Speed.”

On Wednesday, Harvard will launch the Salata Institute for Climate and Sustainability, a cutting-edge initiative designed to leverage and expand the University’s teaching and research in the area and foster cross-disciplinary efforts as a global leader in the climate crisis battle. University leaders and climate experts, along with Melanie and Jean Salata, whose generous gift made the institute possible, will join to mark the occasion. When the initiative was announced in June, Jim Stock, vice provost for climate and sustainability, was named leader of the University-wide venture. In an interview with the Gazette, Stock spoke about how the Salata Institute is poised to bring together the best of Harvard across all of its departments and Schools to advance knowledge and find creative, real-world solutions to the climate crisis.

Q&A

Jim Stock

GAZETTE: In the past, you have said that the scope of the climate problem demands a big tent for solutions. How does Salata help fulfill that need, and what will be different about this approach?

STOCK: The core feature of the Salata Institute is that it’s a central University effort that spans all of Harvard’s Schools. The challenges of climate change affect almost all of what we do here at Harvard. In all our Schools, Harvard experts are doing deep and influential work on the many aspects and implications of climate change. What the Salata Institute brings to the table is the ability take these disparate communities and pull them together at the University level. The biggest problems posed by climate change cut across Schools and disciplines, so by pulling together faculty and students from throughout Harvard, we’ll be better able to tackle those big challenges. Our goal is to harness the forces and strengths of Harvard so that collectively — faculty, students, staff, and alumni — we can put our shoulder to the wheel to really drive meaningful, constructive climate progress.

GAZETTE: How will the institute strengthen Harvard’s role in tackling the challenges faced due to climate change?

STOCK: Let me stress that we are starting from a position of strength. Our faculty include international leaders in the fields of climate science, environmental and climate law, international climate negotiations, engineering, environmental humanities, energy system modeling, business sustainability, and health and ecosystem impacts of climate change, to mention only a few. We have increasingly many courses on climate-related topics. Institutionally, for years the Harvard University Center for the Environment has created a community of climate and environmental scholars and has provided important educational opportunities to our students. And many of our students are deeply committed to making forward progress on the myriad climate challenges we are facing.

Because the Salata Institute is a Harvard-wide initiative, it can pull together and amplify these strengths. It can draw on Harvard’s global convening power. Our Schools are individually prominent — leaders — in their own areas. But it is the University’s global reputation that will provide both a higher level of visibility and a higher degree of impact. The Salata Institute will be able to bring together stakeholders across a wide range of issues. By augmenting those groups with leading thinkers from Harvard and beyond, we will be able to drive practical solutions to the pressing climate change problems of today and tomorrow.

GAZETTE: The institute was announced in June, and you’ve already begun this work. In the past few months, what’s been the first order of business, and what can the Harvard community expect in the coming months?

STOCK: We’ve been working on four parallel tracks. The first track is enhancing research, especially research that goes across the different Schools, spans different disciplines, and focuses on real-world, impactful climate solutions. That research has been spearheaded by a program that we’re calling the Climate Research Clusters Program, which will give significant grants to ambitious, cross-School efforts that are focused on impactful solutions to climate problems. We received 43 first-round proposals, which were presented in a brainstorming session in June, and we’re expecting to announce the awards in the next few months. This will be an ongoing opportunity and an ongoing program of the institute.

A second stream of work is climate education. Back in the spring we set up a committee to review undergraduate and graduate climate education, and the institute will help implement its recommendations. At the center of that work will be meeting the remaining unmet demand for climate courses at Harvard and working across different Schools to provide a coherent and ambitious climate education. We need to prepare our students to be the climate leaders of tomorrow — that’s one of the exciting tasks of the climate initiative and the institute, one for which there is a lot of enthusiasm across our community.

A third thing that we’re working on is hiring new faculty and engaging more faculty on climate-related work. There’s been a lot of energy already in this regard: The Kennedy School made several offers last year in climate-related areas, and the Faculty of Arts and Sciences and SEAS are doing climate-related cluster searches this year. These are significant commitments, which will expand the number of world-leading faculty working on climate issues.

Finally, the fourth area where we’ll be doing work is expanding our external impact. The institute’s ability to pull together faculty from across the University — and to provide resources to support that joint work — combined with its ability to harness Harvard’s global convening power will allow us to reach a new level of visibility and impact. We’ll be rolling this out over the coming year, so stay tuned.

GAZETTE: What do you feel is most important in terms of positioning the institute to achieve its long-term mission?

STOCK: Harvard has such a strong base — and so much potential. There’s tremendous support among the students, faculty, and alumni for doing more. Thanks to the generosity of Melanie and Jean Salata, we now have the foundation for harnessing that enthusiasm. The Salata Institute will enable taking our impact to the next level, so that Harvard is known for its leadership in salient, relevant, and impactful climate research and teaching.

GAZETTE: What should we expect a year from now as we think about the institute and how will you measure success?

STOCK: Progress across the board on collaborative research, education, faculty hiring, and engagement. Looking further ahead, an important goal is for prospective students who want to dedicate their education to tackling climate change to think of Harvard first.

Achieving both our short- and long-term goals will require enthusiastic support and engagement by our full community, and an embrace of the cross-School mission. The Salata Institute will be the hub, the core institution, for achieving that mission, and we are off to an exciting start.

Laser-driven electron propagation. Nanoelectronics implanted through animal embryos. Developing faultless quantum computers. These are just a few examples of the research supported by the Aramont Fund.

The award — celebrating its fifth anniversary of contributing to high-risk, high-reward research across the University — funds the work of outstanding early-career faculty and postdoctoral scholars nominated by the deans of their respective Schools. The fellowship aims to ensure that these scholars — who might go unsupported by most traditional funding options — are able to pursue groundbreaking scientific and technological exploration.

The Aramont Fellowships do more than help kickstart promising careers; they spotlight pathbreaking initiatives and interdisciplinary innovation, with the potential to make great strides in technology, life sciences, physical sciences, and medicine. Established in 2018 with a gift from the Aramont Charitable Foundation, the program supports research at the Faculty of Arts and Sciences, Harvard Medical School, the Harvard T.H. Chan School of Public Health, and the Harvard John A. Paulson School of Engineering and Applied Sciences.

Last year’s winning projects included Jessica Garbern’s work enhancing the survival of cardiomyocytes, cells that manage the heart’s rhythm and can be lost in heart attacks. Garbern is an HMS instructor of pediatrics and an FAS postdoctoral fellow in Stem Cell and Regenerative Biology. Another project, led by FAS assistant professor of physics Matteo Mitrano, produced the first realization of artificial synthetic dimensions in a quantum material driven by a laser. And FAS assistant professor of molecular and cellular biology and of applied physics at the Harvard Paulson School Maxim Prigozhin — working with postdoctoral fellow Sohaib Abdul Rehman — proposed major advancements to electron microscopy, which would help practitioners better identify cellular processes like viral infections.

“For the past five years, the Aramont Fund for Emerging Science Research has fueled tremendous innovation at Harvard. Investing in this critical work and the talented scientists carrying it out is a meaningful commitment to high-risk, high-reward research, as it has the potential to lead to revolutionary scientific breakthroughs,” said John Shaw, vice provost for research, Harry C. Dudley Professor of Structural and Economic Geology, and professor of environmental science and engineering.

This year’s five fellows

Josefina del Mármol
Assistant professor of biological chemistry and molecular pharmacology (HMS) for “Molecular elucidation of human host-seeking in the disease vector Rhodnius prolixus”

Josefina del Mármol’s recent work on insects’ sense of smell paves the way for a deeper understanding of how insects act as disease vectors for humans, a question with significant implications for human health. Although it’s generally understood that smell is extremely important for insects seeking human hosts, the molecular details have been virtually unknown. Del Mármol’s research provides the first atomic-level snapshot of how insect olfactory receptors interact with odor molecules. Her work examines how the South and Central American kissing bug, or Rhodnius prolixus, experiences its sense of smell. Rhodnius prolixus is the major vector of Chagas disease, a life-long affliction that currently impacts an estimated 8 million people worldwide and results in at least 12,000 deaths annually. Combining cryo-electron microscopy, neurophysiology, and drug discovery, her work will shed light on the identity and atomic structure of how Rhodnius prolixus detects human odors, with an aim of developing novel pharmacological tools that disrupt insects’ ability to find human hosts.

Smita Gopinath
Assistant professor of immunology and infectious disease (Harvard Chan School) for “The Role of Vaginal Bacteria in Pregnancy and Preterm Birth”

The resident community of microorganisms within the human vagina, known as its microbiome, is critical to human health, but we understand very little about how it affects immune responses. Unlike the vast intestinal microbiome, the vaginal microbiome consists of a small set of defined communities in two categories: it is either dominated by Lactobacilli with a low diversity of other organisms, or low in Lactobacilli with a high diversity of other organisms. While researchers have been aware of the presence of vaginal Lactobacilli for over a century, little is understood about how they affect our immune responses and physiology. Smita Gopinath hypothesizes that Lactobacilli help control their hosts’ immune response to reduce inflammation, increase resistance to pathogens, and promote host health. She cites that Lactobacilli-dominant vaginal bacterial communities are strongly correlated with pregnancies carried to term (>39 weeks), whereas Lactobacilli-low communities are strongly correlated with pre-term birth. With this project, Gopinath will extend her research group’s initial findings into the field of maternal-fetal immunology to understand how vaginal bacteria influence host health in pregnancy and childbirth.

Heidi Kletzien
Postdoctoral fellow in the Wagers Lab (FAS-SCRB) for “Uncovering Clonal Mechanisms of Head and Neck Cancer Initiation and Progression”

Head and neck cancer (HNC) is one of the 10 most common cancers, and cases are often recurrent with very poor prognoses. Incidence rates have remained relatively unchanged over the past four decades and are expected to rise 66 percent in people over the age of 60 by 2030, due in part to an increase in human papilloma virus (HPV) associated with HNCs. Treatments for HNCs are largely ineffective, with severe side effects that often impact the patient’s quality of life. However, due to poor understanding of the genetic background of HNC and how it originates, treatments have remained static over the past century. Using gene editing technology, Heidi Kletzien will introduce mutations in head and neck tissue stem cells order to observe and understand the particular genes and pathways that cause HNC. Kletzien aims to uncover the mechanisms of how these cancers develop, with the goal of developing more innovative and effective treatments.

Richard Liu
Assistant professor of chemistry and chemical biology (FAS) for “Organic Molecules That Mimic Transition-Metal Catalysts for Sustainable Chemical Synthesis”

Catalysts based on noble metals such as palladium and rhodium have become indispensable tools for manufacturing pharmaceuticals and other chemical substances. However, their use can pose difficulties, including supply chain issues due to geopolitical conflicts and increasing scarcity and (although there are strict regulations in place to protect human and environmental health) their toxicity. Discovering sustainable alternative catalysts is a critically important objective in the field of synthetic chemistry. Richard Liu proposes a unique strategy: the design of organic pseudotransition materials, or metal-free molecules capable of performing the same chemical reactions noble metals do. In addition to the practical advantage of a sustainable replacement, Liu also envisions an opportunity to fundamentally reimagine basic principles of bonding and reactivity of metal-based compounds. He hopes not only to imitate the chemistry of noble metals but to invent pseudometals with wholly unprecedented properties and behavior.

Haichao Wu
Postdoctoral fellow in the Aizenberg Lab (SEAS) for “Microrobots-Embedded Self-Cleaning Membranes for Rationally Designed Separation Processes”

Filtration systems in industrial settings such as water treatment plants, pharmaceutical sterilization facilities, and beverage and dairy processing use a process called membrane separation, where a membrane filters out specific substances. Although membrane separation is widely used, the procedure suffers from performance limitations due to fouling of the membrane during filtration, which reduces its lifespan and limits effectiveness. Drawing upon the concept of self-propulsion, in which microorganisms convert energy from their environment into motion, Wu will introduce self-propelling mechanisms into the filtering process. This concept has already been applied in micro- and nanobot technology, with success in biomedical applications like drug delivery and molecular diagnosis. Wu posits that self-propulsion technology can effectively halt internal membrane deterioration, and that the addition of microrobots will facilitate the separation process, leading to enhanced efficiency. His work aims to inform the development of next-generation membranes with self-cleaning properties.

NASA’s $10 billion James Webb Space Telescope is expected to tell the story of the universe with unprecedented clarity over the next decade. But what if we misread the details?

In a study published in Nature Astronomy, researchers from Harvard and MIT warn that the models astronomers use to decode light-based signals from the atmospheres of exoplanets may not be precise enough to accurately represent the data the new telescope is capturing. They say that if these models aren’t improved, the tools will run into an accuracy wall and, as a result, calculations on planetary properties such as temperature, pressure, and elemental composition could be off by an order of magnitude.

“What we have to do is simulate the atmosphere with our computational models and compare that to the reality of what JWST sees on these planets, but if our models are incomplete or incorrect, then you can imagine that this comparison of the model to reality won’t quite work and will lead to incorrect interpretations,” said Clara Sousa-Silva, an assistant physics professor at Bard College and a former fellow at the Center for Astrophysics | Harvard & Smithsonian, where much of the research took place.

“Our study does show that if we want to maximize the number and the quality of these insights that we can get from the amazing JWST data, then we still have a lot of work to do on Earth because there’s just no standardized, foolproof way to interpret our observations of alien atmospheres,” Sousa-Silva added.

CfA scientists Iouli Gordon, Robert J. Hargreaves, and Roman V. Kochanov also worked on the study. It was led by Prajwal Niraula and Julien de Wit of MIT.

The scientists say the problem lies with the opacity models astronomers use to describe and predict the composition of exoplanet atmospheres. The process starts with starlight. As a planet passes its star, stellar light passes through its atmosphere. Observatories such as the Webb measure this light, absorbing specific colors and wavelengths that correspond to different atoms and molecules in the atmosphere.

Astronomers break down the first layer of this data to see if something like water vapor is present. Then come opacity models, which measure how light interacts with matter to reveal atmospheric properties. This is where researchers detected the problem.

When they mocked up levels of data the Webb might collect on exoplanets and ran them through the most commonly used opacity models, they found that the models weren’t up to par with the Webb’s advanced precision.

The opacity models produced figures on atmospheric conditions that were deemed “good fits” with the data but could result in multiple interpretations. The researchers found measurements were off by about 0.5 to 1 dex, otherwise known as an order of magnitude, a number multiplied to the tenth power. They say this creates an incredible range of possibilities, and current models can’t distinguish those that are accurate or wrong.

For example, one group could determine a planet’s temperature is about 80 degrees F, a balmy paradise. Another group, looking at that same planet, could interpret the data to say the planet is a scorching wasteland at 572 degrees F. The current models also wouldn’t be able to tell whether a planet’s atmosphere is 5 or 25 percent water.

The implications of misinterpretations like this could make the difference in determining whether an exoplanet could support life.

The paper provides some ideas for refining current models or creating better ones, but none are ready to go. To get there, the researchers say it will require gathering much more Webb planetary atmosphere measurements, and a lot of laboratory and theoretical work carrying out new measurements and calculations to refine our understanding of how light interacts with various molecules.

“These data will then have to be validated and disseminated through spectroscopic databases,” Gordon said. “This will take a few years, but it is definitely a feasible solution.”

Astrophysicists have performed a powerful new analysis that places the most precise limits yet on the composition and evolution of the universe. With this analysis, dubbed Pantheon+, cosmologists find themselves at a crossroads.

Pantheon+ convincingly finds that the cosmos is composed of about two-thirds dark energy and one-third matter — mostly in the form of dark matter — and is expanding at an accelerating pace over the last several billion years. However, Pantheon+ also cements a major disagreement over the pace of that expansion that has yet to be solved.

By putting prevailing modern cosmological theories, known as the Standard Model of Cosmology, on even firmer evidentiary and statistical footing, Pantheon+ further closes the door on alternative frameworks accounting for dark energy and dark matter. Both are bedrocks of the Standard Model of Cosmology but have yet to be directly detected and rank among the model’s biggest mysteries. Following through on the results of Pantheon+, researchers can now hone explanations for the ostensible cosmos.

“With these Pantheon+ results, we are able to put the most precise constraints on the dynamics and history of the universe to date,” says Dillon Brout, an Einstein Fellow at the Center for Astrophysics | Harvard & Smithsonian. “We’ve combed over the data and can now say with more confidence than ever before how the universe has evolved over the eons and that the current best theories for dark energy and dark matter hold strong.”

Brout is the lead author of a series of papers describing the new Pantheon+ analysis, published jointly today in a special issue of The Astrophysical Journal.

Pantheon+ is based on the largest dataset of its kind, comprising more than 1,500 stellar explosions called Type Ia supernovae. These bright blasts occur when white dwarf stars — remnants of stars like our sun — accumulate too much mass and undergo a runaway thermonuclear reaction. Because Type Ia supernovae outshine entire galaxies, the stellar detonations can be glimpsed at distances exceeding 10 billion light years, or back through about three-quarters of the universe’s total age. Given that the supernovae blaze with nearly uniform intrinsic brightnesses, scientists can use the explosions’ apparent brightness, which diminishes with distance, along with redshift measurements as markers of time and space. That information, in turn, reveals how fast the universe expands during different epochs, which is then used to test theories of the fundamental components of the universe.

The breakthrough discovery in 1998 of the universe’s accelerating growth was thanks to a study of Type Ia supernovae in this manner. Scientists attribute the expansion to an invisible energy, therefore monikered dark energy, inherent to the fabric of the universe itself. Subsequent decades of work have continued to compile ever-larger datasets, revealing supernovae across an even wider range of space and time, and Pantheon+ has now brought them together into the most statistically robust analysis to date.

“In many ways, this latest Pantheon+ analysis is a culmination of more than two decades’ worth of diligent efforts by observers and theorists worldwide in deciphering the essence of the cosmos” says Adam Riess, one of the winners of the 2011 Nobel Prize in physics for the discovery of the accelerating expansion of the universe and the Bloomberg Distinguished Professor at Johns Hopkins University and the Space Telescope Science Institute in Baltimore, Maryland. Riess is also an alum of Harvard University, holding a Ph.D. in astrophysics.

Brout’s own career in cosmology traces back to his undergraduate years at JHU, where he was taught and advised by Riess. There Brout worked with then-Ph.D.-student and Riess-advisee Dan Scolnic, who is now an assistant professor of physics at Duke University and another co-author on the new series of papers.

Several years ago, Scolnic developed the original Pantheon analysis of approximately 1,000 supernovae.

Now, Brout and Scolnic and their new Pantheon+ team have added some 50 percent more supernovae data points in Pantheon+, coupled with improvements in analysis techniques and addressing potential sources of error, which ultimately has yielded twice the precision of the original Pantheon.

Taking the data as a whole, the new analysis holds that 66.2 percent of the universe manifests as dark energy, with the remaining 33.8 percent being a combination of dark matter and matter. To arrive at even more comprehensive understanding of the constituent components of the universe at different epochs, Brout and colleagues combined Pantheon+ with other strongly evidenced, independent and complementary measures of the large-scale structure of the universe and with measurements from the earliest light in the universe, the cosmic microwave background.

Another key Pantheon+ result relates to one of the paramount goals of modern cosmology: nailing down the current expansion rate of the universe, known as the Hubble constant. Pooling the Pantheon+ sample with data from the SH0ES (Supernova H0 for the Equation of State) collaboration, led by Riess, results in the most stringent local measurement of the current expansion rate of the universe.

Pantheon+ and SH0ES together find a Hubble constant of 73.4 kilometers per second per megaparsec with only 1.3 percent uncertainty. Stated another way, for every megaparsec, or 3.26 million light years, the analysis estimates that in the nearby universe, space itself is expanding at more than 160,000 miles per hour.

However, observations from an entirely different epoch of the universe’s history predict a different story. Measurements of the universe’s earliest light, the cosmic microwave background, when combined with the current Standard Model of Cosmology, consistently peg the Hubble constant at a rate that is significantly less than observations taken via Type Ia supernovae and other astrophysical markers. This sizable discrepancy between the two methodologies has been termed the Hubble tension.

The new Pantheon+ and SH0ES datasets heighten this Hubble tension. In fact, the tension has now passed the important 5-sigma threshold (about one-in-a-million odds of arising due to random chance) that physicists use to distinguish between possible statistical flukes and something that must accordingly be understood. Reaching this new statistical level highlights the challenge for both theorists and astrophysicists to try and explain the Hubble constant discrepancy.

“We thought it would be possible to find clues to a novel solution to these problems in our dataset, but instead we’re finding that our data rules out many of these options and that the profound discrepancies remain as stubborn as ever,” says Brout.

The Pantheon+ results could help point to where the solution to the Hubble tension lies. “Many recent theories have begun pointing to exotic new physics in the very early universe, however such unverified theories must withstand the scientific process and the Hubble tension continues to be a major challenge,” says Brout.

Overall, Pantheon+ offers scientists a comprehensive lookback through much of cosmic history. The earliest, most distant supernovae in the dataset gleam forth from 10.7 billion light years away, meaning from when the universe was roughly a quarter of its current age. In that earlier era, dark matter and its associated gravity held the universe’s expansion rate in check. Such state of affairs changed dramatically over the next several billion years as the influence of dark energy overwhelmed that of dark matter. Dark energy has since flung the contents of the cosmos ever-farther apart and at an ever-increasing rate.

“With this combined Pantheon+ dataset, we get a precise view of the universe from the time when it was dominated by dark matter to when the universe became dominated by dark energy,” says Brout. “This dataset is a unique opportunity to see dark energy turn on and drive the evolution of the cosmos on the grandest scales up through present time.”

Studying this changeover now with even stronger statistical evidence will hopefully lead to new insights into dark energy’s enigmatic nature.

“Pantheon+ is giving us our best chance to date of constraining dark energy, its origins, and its evolution,” says Brout.

Their plot worked perfectly.

Harvard scientists on Monday conspired with one of the nation’s top barbecue chefs to slip some science into his cherry-wood-smoked pork ribs. The academic bits came compliments of David Weitz and Pia Sörensen, organizers of the 13-year-old “Science and Cooking” lecture series. Its latest installment Monday evening was a damp and smoky, affair that, despite the threat of rain, lured an audience of about 80 of the barbecue-curious to the patio outside Harvard’s Laboratory for Integrated Science and Engineering.

The smoke came compliments of Bryan Furman, an Atlanta pitmaster who in 2019 was named one of Food and Wine magazine’s best new chefs. Furman, whose appearance Monday was an encore from a year earlier, is a former welder who has blended his knowledge of the transformative power of heat with an appreciation for the heritage hogs raised on his grandparents’ South Carolina farm, where he spent time growing up.

Furman said science was one of his favorite subjects, but his teachers weren’t able to make it as accessible, practical — and alluring — as he aimed to make his talk, “The Thermodynamics of Barbecue.” Barbecue, he said, could be used as a medium to teach not just science, but art and business as well.

“This wasn’t what they were talking about when I was in school,” Furman said. “When you’re teaching students like this, it keeps them more involved and interested, compared to just sitting in class.”

Weitz, Mallinckrodt Professor of Physics and Applied Physics at the Harvard John A. Paulson School of Engineering and Applied Sciences, kicked off the session with some scientific basics, describing diffusion of compounds and heat, both of which work to impart texture and flavor during the smoking process. He also offered a “Science and Cooking” standard: the equation of the week, which elicited appreciative applause. This particular one describes the distance that heat diffuses into a substance, L=√4Dt, where L is the distance heat diffuses, t is the time heat has to work, and D is the substance’s diffusion coefficient.

Weitz noted that the diffusion coefficients were similar for several very different foods — beef, strawberries, chicken, potatoes, and water — mainly because water is a major component of each.

In the 480 B.C. Battle of Himera, Greek forces defeated the invading Carthaginians in a victory that ushered in a period of peace and prosperity across their world. But while historians such as Herodotus hailed the victory as a triumph of Greek heroism and fortitude, studies of recently discovered mass graves have revealed that the combatants included substantial numbers of non-Greek fighters. A new study found that the men who died violently likely hailed from as far away as the Baltic region and the Eurasian steppe, giving insights into the nature of these wars and movements of people over extraordinarily long distances in the Classical world.

The new paper, “The diverse genetic origins of a Classical period Greek army,” published in Proceedings of the National Academy of Sciences, takes a genomic look at those foreign fighters. A previous study used isotopes to identify three-quarters of those in the mass graves as “non-local.” Now, the archaeologists from that study — including Professor of Genetics and Human Evolutionary Biology David Reich, co-first authors Laurie Rietsema (University of Georgia) and Britney Kyle (University of Northern Colorado), were able to carry out an in-depth dive into genome-wide data from 16 individuals from these mass graves (as well as 38 other ancient people from Sicily). Their analysis revealed that individuals from the mass graves, assumed to be largely mercenaries, hailed from places as far-flung as Ukraine, the Baltic region (modern-day Latvia), and Thrace (modern-day Bulgaria), said Reich.

Going into the study, “We already had an idea that people from lots of regions must have participated in this battle, but there was no clue yet as to where they came from,” said Alissa Mittnik, the postdoc in Reich’s lab who led the genetic analysis and another co-first author.

History was no help. “Much was written about this event from the historical records, but all historical information has biases,” said Reich. Documenting the apparent heroism of the Greeks at this battle, as well as at battles with invading Persians around the same time at Salamis and Thermopylae, the other end of the Greek world, “was important to Greek identity in this period.”

One aspect of these accounts has been the makeup of the armies. “While it is known that in this period in time mercenaries were widely used, Greek historians didn’t mention the participation of mercenaries at Himera,” said Mittnik. “They would have been people that would have been considered by the Greeks as foreign barbarians.”

Using DNA mined from bones and teeth, the team provides surprising information about the origins of these non-Greek fighters. “We have data from tens of thousands, and sometimes even more than a million positions in the genome,” explained Reich. “Such data is similar in quality data to what one gets from sending your DNA to a personal ancestry testing company.” The data allowed the team to compare the ancestry of the people from ancient Sicily with the ancestry of others with “exquisite accuracy,” said Reich.

“Combining the genetic and the isotopic results tells us about the genetic ancestry of people and gives powerful clues about where they grew up.” For example, he said, “Two individuals have ancestry typical of the Baltic region at the time, two have ancestry typical of the Northern Balkans, and two have ancestry typical of the steppes north of the Black Sea.”

These findings shed light on patterns of movement through the ancient world. “This provides direct evidence of people traveling long distances in their lifetime and shows that a motivation for such travel would have been not just trade but participation in warfare,” said Mittnik.

“War,” added Reich, “seems to have drawn people from particularly far-flung places.”

For Mittnik, who has started her own research group in Germany, this work fits well within a larger program. “I’m interested in using ancient DNA to gain insight into the dynamics of communities,” she said.” “I also work on reconstructing family trees and studying patterns in these pedigrees to learn what they can show about social organization.”

Reich said the possibilities are global. “Genetic data complement isotopic and archaeological data, and by combining them, we obtain a richer and more nuanced understanding of the past.”

In October 2018, a small star was ripped to shreds when it wandered too close to a black hole in a galaxy located 665 million light years away from Earth. Though it may sound thrilling, the event did not come as a surprise to astronomers who occasionally witness these violent incidents while scanning the night sky.

But nearly three years after the massacre, the same black hole is lighting up the skies again — and it hasn’t swallowed anything new, scientists say.

“This caught us completely by surprise — no one has ever seen anything like this before,” says Yvette Cendes, a research associate at the Center for Astrophysics | Harvard & Smithsonian (CfA) and lead author of a new study analyzing the phenomenon.

The team concludes that the black hole is now ejecting material traveling at half of the speed of light, but are unsure why the outflow was delayed by several years. The results, described this week in the Astrophysical Journal, may help scientists better understand black holes’ feeding behavior, which Cendes likens to “burping” after a meal.

The team spotted the unusual outburst while revisiting tidal disruption events (TDEs) — when encroaching stars are spaghettified by black holes — that occurred over the last several years.

Radio data from the Very Large Array (VLA) in New Mexico showed that the black hole had mysteriously reanimated in June 2021. Cendes and the team rushed to examine the event more closely.

“We applied for Director’s Discretionary Time on multiple telescopes, which is when you find something so unexpected, you can’t wait for the normal cycle of telescope proposals to observe it,” Cendes explains. “All the applications were immediately accepted.”

The team collected observations of the TDE, dubbed AT2018hyz, in multiple wavelengths of light using the VLA, the ALMA Observatory in Chile, MeerKAT in South Africa, the Australian Telescope Compact Array in Australia, and the Chandra X-Ray Observatory and the Neil Gehrels Swift Observatory in space.

Radio observations of the TDE proved the most striking.

“We have been studying TDEs with radio telescopes for more than a decade, and we sometimes find they shine in radio waves as they spew out material while the star is first being consumed by the black hole,” says Edo Berger, professor of astronomy at Harvard University and the CfA, and co-author on the new study. “But in AT2018hyz there was radio silence for the first three years, and now it’s dramatically lit up to become one of the most radio luminous TDEs ever observed.”

Sebastian Gomez, a postdoctoral fellow at the Space Telescope Science Institute and co-author on the new paper, says that AT2018hyz was “unremarkable” in 2018 when he first studied it using visible light telescopes, including the 1.2-m telescope at the Fred Lawrence Whipple Observatory in Arizona.

Gomez, who was working on his doctoral dissertation with Berger at the time, used theoretical models to calculate that the star torn apart by the black hole was only one tenth the mass of our Sun.

“We monitored AT2018hyz in visible light for several months until it faded away, and then set it out of our minds,” Gomez says.

TDEs are well-known for emitting light when they occur. As a star nears a black hole, gravitational forces begin to stretch, or spaghettify, the star. Eventually, the elongated material spirals around the black hole and heats up, creating a flash that astronomers can spot from millions of light years away.

Some spaghettified material occasionally gets flung out back into space. Astronomers liken it to black holes being messy eaters — not everything they try to consume makes it into their mouths.

But the emission, known as an outflow, normally develops quickly after a TDE occurs — not years later. “It’s as if this black hole has started abruptly burping out a bunch of material from the star it ate years ago,” Cendes explains.

In this case, the burps are resounding.

The outflow of material is traveling as fast as 50 percent the speed of light. For comparison, most TDEs have an outflow that travels at 10 percent the speed of light, Cendes says.

“This is the first time that we have witnessed such a long delay between the feeding and the outflow,” Berger says. “The next step is to explore whether this actually happens more regularly and we have simply not been looking at TDEs late enough in their evolution.”

Additional co-authors on the study include Kate Alexander and Aprajita Hajela of Northwestern University; Ryan Chornock, Raffaella Margutti and Daniel Brethauer of the University of California, Berkley; Tanmoy Laskar of Radboud University; Brian Metzger of Columbia University; Michael Bietenholz of York University and Mark Wieringa of the Australia Telescope National Facility.