The world of black holes has long been divided into three categories: stellar-mass black holes (about five to 50 times the mass of the sun), supermassive black holes (millions to billions of times the mass of the sun), and intermediate-mass black holes with masses somewhere in between. While we know that intermediate-mass black holes should exist, little is known about their origins or characteristics – they are considered the rare “missing links” in black hole evolution.

However, four new studies have shed new light on this mystery. The research was led by a team in the lab of Assistant Professor Karan Jani, who also serves as the founding director of the Vanderbilt Lunar Labs Initiative. The work was funded by the National Science Foundation and the Vanderbilt Office of the Vice Provost for Research and Innovation.

The primary paper, “Properties of ‘Lite’ Intermediate-Mass Black Hole Candidates in LIGO-Virgo’s Third Observing Run,” was published in Astrophysical Journal Letters and led by Lunar Labs postdoctoral fellow Anjali Yelikar and astrophysics Ph.D. candidate Krystal Ruiz-Rocha. The team reanalyzed data from the Nobel-Prize winning Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors in the U.S. and the Virgo detector in Italy.

The researchers found that these waves corresponded to mergers of black holes greater than 100 to 300 times the mass of the sun, making them the heaviest gravitational-wave events recorded in astronomy. “Black holes are the ultimate cosmic fossils,” Jani said. “The masses of black holes reported in this new analysis have remained highly speculative in astronomy. This new population of black holes opens an unprecedented window into the very first stars that lit up our universe.”

Earth-based detectors like LIGO capture only a split second of the final collision of these “lightweight” intermediate-mass black holes, making it challenging to determine how the universe creates them. To tackle this, Jani’s lab turned to the upcoming European Space Agency and NASA’s Laser Interferometer Space Antenna (LISA) mission, launching in the late 2030s.

In two additional studies published in Astrophysical Journal, “A Sea of Black Holes: Characterizing the LISA Signature for Stellar-origin Black Hole Binaries,” led by Ruiz-Rocha, and “A Tale of Two Black Holes: Multiband Gravitational-wave Measurement of Recoil Kicks,” led by former summer research intern Shobhit Ranjan, the team showed LISA can track these black holes years before they merge, shedding light on their origin, evolution, and fate.

Detecting gravitational waves from black hole collisions requires extreme precision – like trying to hear a pin drop during a hurricane. In a fourth study also published in Astrophysical Journal, “No Glitch in the Matrix: Robust Reconstruction of Gravitational Wave Signals under Noise Artifacts,” the team showcased how artificial intelligence models guarantee that signals from these black holes remain uncorrupted from environmental and detector noise in the data. The paper was led by postdoctoral fellow Chayan Chatterjee and expands upon Jani’s AI for New Messengers Program, a collaboration with the Data Science Institute.

“We hope this research strengthens the case for intermediate-mass black holes as the most exciting source across the network of gravitational-wave detectors from Earth to space,” Ruiz-Rocha said. “Each new detection brings us closer to understanding the origin of these black holes and why they fall into this mysterious mass range.”

Moving forward, Yelikar said the team will explore how intermediate-mass black holes could be observed using detectors on the moon.

“Access to lower gravitational-wave frequencies from the lunar surface could allow us to identify the environments these black holes live in – something Earth-based detectors simply can’t resolve,” she said.

In addition to continuing this research, Jani will also be working with the National Academies of Sciences, Engineering, and Medicine on a NASA-sponsored study to identify high-value lunar destinations for human exploration to address decadal-level science objectives. As part of his participation in this study, Jani will be contributing to the Panel on Heliophysics, Physics, and Physical Science, to identify and articulate the science objectives related to solar physics, space weather, astronomy, and fundamental physics that would be most enabled by human explorers on the moon.

“This is an exciting moment in history – not just to study black holes, but to bring scientific frontiers together with the new opportunity of training the next generation of students whose discoveries will be shaped by, and made from, the moon,” Jani said.

The discovery of an object called ASKAP J1832-0911 has left astronomers puzzled. This mysterious entity emits pulses of radio waves and X-rays for two minutes every 44 minutes. What makes this finding even more intriguing is that it’s the first time such an object, known as a long-period transient (LPT), has been detected in X-rays.

The team behind this discovery used the ASKAP radio telescope to detect the radio signals, which they then correlated with X-ray pulses detected by NASA’s Chandra X-ray Observatory. This coincidence of observations allowed them to confirm that ASKAP J1832-0911 is indeed emitting both types of radiation.

LPTs are a relatively recent discovery, with only ten such objects found so far. Scientists still have no clear explanation for what causes these signals or why they ‘switch on’ and ‘switch off’ at such long, regular intervals. Some theories suggest that ASKAP J1832-0911 could be a magnetar or a pair of stars in a binary system with one star being a highly magnetised white dwarf.

However, even these theories don’t fully explain what’s being observed. This discovery might indicate the existence of new types of physics or models of stellar evolution. By detecting objects like ASKAP J1832-0911 using both X-rays and radio waves, scientists hope to find more examples and gain a better understanding of their nature.

The discovery of ASKAP J1832-0911 is not only significant for the scientific community but also showcases an incredible teamwork effort between researchers across the globe. The study’s findings have been published in Nature, and the object itself is located in our Milky Way galaxy about 15,000 light-years from Earth.

A landmark study published in Nature has established a new benchmark in modeling the universe’s most extreme events: the collisions of black holes and neutron stars. This research, led by Professor Jan Plefka at Humboldt University of Berlin and Queen Mary University London’s Dr Gustav Mogull, provides unprecedented precision in calculations crucial to understanding gravitational waves.

Using cutting-edge techniques inspired by quantum field theory, the team calculated the fifth post-Minkowskian (5PM) order for observables such as scattering angles, radiated energy, and recoil. A groundbreaking aspect of the work is the appearance of Calabi-Yau three-fold periods – geometric structures rooted in string theory and algebraic geometry – within the radiative energy and recoil.

These structures, once considered purely mathematical, now find relevance in describing real-world astrophysical phenomena. With gravitational wave observatories like LIGO entering a new phase of sensitivity and next-generation detectors such as LISA on the horizon, this research meets the increasing demand for theoretical models of extraordinary accuracy.

Dr Mogull explained the significance: “While the physical process of two black holes interacting and scattering via gravity we’re studying is conceptually simple, the level of mathematical and computational precision required is immense.” Benjamin Sauer, PhD candidate at Humboldt University of Berlin adds: “The appearance of Calabi-Yau geometries deepens our understanding of the interplay between mathematics and physics. These insights will shape the future of gravitational wave astronomy by improving the templates we use to interpret observational data.”

This precision is particularly important for capturing signals from elliptic bound systems, where orbits more closely resemble high-velocity scattering events, a domain where traditional assumptions about slow-moving black holes no longer apply.

Gravitational waves, ripples in spacetime caused by accelerating massive objects, have revolutionized astrophysics since their first detection in 2015. The ability to model these waves with precision enhances our understanding of cosmic phenomena, including the “kick” or recoil of black holes after scattering – a process with far-reaching implications for galaxy formation and evolution.

Perhaps most tantalizingly, the discovery of Calabi-Yau structures in this context connects the macroscopic realm of astrophysics with the intricate mathematics of quantum mechanics. “This could fundamentally change how physicists approach these functions,” said team member Dr Uhre Jakobsen of Max Planck Institute for Gravitational Physics and Humboldt University of Berlin. “By demonstrating their physical relevance, we can focus on specific examples that illuminate genuine processes in nature.”

The project utilized over 300,000 core hours of high-performance computing at the Zuse Institute Berlin to solve the equations governing black hole interactions, demonstrating the indispensable role of computational physics in modern science. “The swift availability of these computing resources was key to the success of the project,” adds PhD candidate Mathias Driesse, who led the computing efforts.

Professor Plefka emphasized the collaborative nature of the work: “This breakthrough highlights how interdisciplinary efforts can overcome challenges once deemed insurmountable. From mathematical theory to practical computation, this research exemplifies the synergy needed to push the boundaries of human knowledge.”

This breakthrough not only advances the field of gravitational wave physics but also bridges the gap between abstract mathematics and the observable universe, paving the way for discoveries yet to come. The collaboration is set to expand its efforts further, exploring higher-order calculations and utilizing the new results in future gravitational waveform models. Beyond theoretical physics, the computational tools used in this study, such as KIRA, also have applications in fields like collider physics.

This achievement was the result of extensive international collaboration and advanced mathematical and computational methods. The groundwork for the study was laid in Plefka’s group at Humboldt University of Berlin, where the Worldline Quantum Field Theory formalism was pioneered together with Dr Gustav Mogull. Over time, the collaboration expanded to include world-leading specialists such as Dr Johann Usovitsch, who moved from CERN to Humboldt University of Berlin and is the developer of the KIRA software, as well as mathematical physicists Dr Christoph Nega (Technical University of Munich) and Professor Albrecht Klemm (University of Bonn), leading experts on Calabi-Yau manifolds.

The project received key funding through Professor Plefka’s ERC Advanced Grant GraWIToH, the DFG-funded research unit “Gravitational Physics,” and Dr Mogull’s Royal Society University Research Fellowship, Gravitational Waves from Worldline Quantum Field Theory.