Current Research Highlights

The space around galaxies might not glow brightly in telescopes, but it is, in fact, filled with gases at vastly different temperatures. From plasma at a million degrees Celsius to much colder, tiny, cold clouds at temperatures that can be found on Earth. Understanding how these gases interact is key to explaining how galaxies grow, form stars, and evolve. But the vast temperature difference has proved to be a significant challenge for simulations, as it also results in a big difference in densities.  A team of scientists from MPA and AIP (Potsdam) has now developed a new model, MOGLI, that can track these interactions in unprecedented detail. By treating hot and cold gas as two coupled components that exchange material and energy, a multifluid approach, developed in engineering circles for numerous terrestrial applications, allows large cosmological simulations to capture the hidden life of cold gas. more

When two stars orbit close together, one star can transfer material to its companion, dramatically changing both stars' evolution. However, how much of this transferred material actually stays with the receiving star has remained one of the biggest mysteries in binary star physics. Using a new sample of 16 carefully studied binary systems, MPA scientists have now discovered that binary stars are much more efficient at keeping transferred material than previously thought, with many systems retaining more than half of the mass that was donated. This finding challenges decades of theoretical assumptions and has profound implications for our understanding of stellar evolution, affecting everything from the types of supernovae we observe to the formation of gravitational wave sources, X-ray binaries, and exotic stellar objects like blue stragglers. more

Black holes with masses between the stellar and supermassive regime are among the most elusive objects in the Universe. These intermediate-mass black holes are believed to reside in many dwarf galaxies. Using new, high-resolution supercomputer simulations, MPA scientists discovered that nuclear star clusters — compact, massive clusters of stars at the centres of galaxies — may be key to enabling these black holes to grow, thus shedding light on the origins of supermassive black holes. more

Quasars are active supermassive black holes located at the centres of massive galaxies that emit energy levels that far exceed the binding energy of their host galaxies. This substantial amount of energy has the potential to impact the gas within and around the galaxies, thereby influencing their evolution. While the importance of this process is acknowledged, its details are still the subject of significant debate. An international team of researchers led by MPA scientists has now obtained observations of the most extensive sample of hydrogen structures surrounding quasars in the early universe to better understand this feedback process. The data reveal how the gas responds to the energy released by the supermassive black holes over distances of several hundred thousand light years, providing a new way to study the impact of quasars on galaxy evolution. 
  more

Imagine a star not crashing into a supermassive black hole in a fiery explosion, but instead slowly spiraling in, circling closer and closer to its horizon. This is the story of a sub-giant star that is stripped of its hydrogen layer by a black hole companion with a few million solar masses. The left-over helium core is gently drawn in due to strong gravitational wave emission and can be placed so close to the supermassive black hole that it becomes a promising gravitational wave source for the future detector LISA (Laser Interferometer Space Antenna). This scenario has been recently investigated by a team at MPA. more

Galaxies are surrounded by a large reservoir of gas called the circumgalactic medium (CGM), where they refuel and recycle the gas for forming stars and growing in mass. This gas is extremely dim, with current observations being limited to spectral lines that are hard to interpret. It is therefore challenging to understand the mass, distribution, and physical conditions prevalent in the CGM. Recently, a group of researchers at MPA serendipitously discovered bright oxygen emission around a massive galaxy group in the distant universe using the James Webb Space Telescope (JWST). In collaboration with other international scientists and by combining various observations, the study provides a detailed and unprecedented view of the CGM, showing how galaxies influence the gas and their environment. more

Ground-based gravitational wave detectors like LIGO and Virgo have brought significant attention to binary systems composed of black holes and neutron stars as gravitational wave sources. However, two white dwarfs in a binary system are expected to be far more numerous. In particular, the pre-merger phase of double white dwarfs could lead to high-energy astrophysical events that would emit gravitational waves detectable by the European Space Agency’s upcoming Laser Interferometer Space Antenna (LISA) mission. Understanding how these double white dwarfs form is essential to interpreting the future LISA data. For the first time, researchers at the Max Planck Institute for Astrophysics (MPA) have now quantitatively assessed the impact of triple evolution on LISA sources. This study underscores the importance of triple interactions in the formation of double white dwarfs, revealing previously unexplored pathways that contribute to the gravitational-wave sources LISA will observe.
  more

The nature of dark matter is still very much unknown; viable candidates range from microsopic elementary particles to black holes with masses many times that of the Sun. Researchers at MPA, Carnegie Observatories, and the University of Sussex have recently made concrete and reliable predictions for how the Universe would look if dark matter consists entirely of massive black holes: they performed the first self-consistent study of how structure would form in such a Universe, and how many of these black holes merge and emit observable gravitational waves. more

The expansion rate of the Universe, quantified by the Hubble constant (H₀), remains one of the most debated quantities in cosmology. Measurements based on nearby objects yield a higher value than those inferred from observations of the early Universe—a discrepancy known as the "Hubble tension". Researchers at the Max Planck Institute for Astrophysics and their collaborators have now presented a new, independent determination of H₀ using Type II supernovae. By modeling the light from these exploding stars with advanced radiation transport techniques, they were able to directly measure distances without relying on the traditional distance ladder. The resulting H₀ value agrees with other local measurements and adds to the growing body of evidence for the Hubble tension, offering an important cross-check and a promising path toward resolving this cosmic puzzle. more

Most stars form in clusters, deeply embedded in the densest and coldest cores of giant molecular gas clouds. A few million years into the formation of a cluster the remaining gas is finally expelled by supernova explosions. Thereafter the clusters lose stars in the galactic tidal field and eventually disrupt. This entire life-cycle is very difficult to observe. Star clusters begin their lives deeply embedded in their birth clouds and are invisible to most observatories and the disruption of a single cluster can take tens of millions of years or more. An international team led by researchers at MPA has presented a new high-resolution supercomputer simulation, which can follow entire galactic star cluster life-cycles from birth to disruption and sheds light on the unobservable phases of star cluster evolution. more

The formation and evolution of galaxies are among the most complex challenges in astrophysics. Recent advancements with instruments like JWST and ALMA have shed light on high-redshift galaxies – those that existed billions of years ago. However, most theoretical models are tuned to match galaxies in the local universe. Researchers from the Max Planck Institute for Astrophysics and the University of Bonn now comprehensively evaluated the Munich semi-analytical model L-GALAXIES using the latest observations and found that while the model aligns well with the properties of local galaxies, it struggles with key aspects of high-redshift galaxies. Particularly, the study highlights critical issues with the model’s predictions of quenched galaxies, those that have ceased star formation. Their results suggest a need to revise the implementation of processes driving star formation quenching, including supermassive black hole feedback and galaxy mergers.
  more

The distribution of matter in the universe is predicted by supercomputer simulations to occur in a network of filaments, known as the "cosmic web", where galaxies form and evolve. The vast majority of this intricate structure is in the form of diffuse hydrogen gas, so rarefied that it is extremely challenging to observe it directly. A collaboration led by MPA researchers has targeted the active supermassive black holes of galaxy pairs at close separations to reveal the connecting filamentary structures of the cosmic web in the early universe. The results are promising and unveil evidence for such structures stretching between the observed pairs, ultimately providing excellent targets for future ultra-deep observations. more