In January, Prof. Dr. Tobias Bonhoeffer, Advisor to the MPG President on Africa Affairs, visited the Partner Group of the Max Planck Institute for Astrophysics at Kyambogo University in Uganda, led by Dr. Benard Nsamba. Prof. Bonhoeffer met with the university's top management and participated in a productive collaborative board meeting, discussing future research initiatives and opportunities for deeper cooperation.
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In recent years, a tantalizing hint of new physics was found in polarization data of the cosmic microwave background from the WMAP and Planck space missions. The so called “cosmic birefringence” is violating parity symmetry, however, the validity of the result was questioned, because the analysis method depends on the modeling of Galactic dust emission. Now, the cosmological interpretation of the signal gains strength as MPA scientists find a comparable effect in the newest data release from the Atacama Cosmology Telescope without relying on Galactic emission. If further independent observations confirm this result as a genuine cosmological signal, it would have profound implications for the fundamental laws of physics and shed light on the mysterious nature of dark matter and dark energy. more

A pan-European group of astronomers has used newly developed computer technology to solve a 100 year-old puzzle. While most galaxies in our neighborhood move away from us almost as expected for an unperturbed cosmic expansion, our nearest giant neighbour is approaching at high speed. Systematic numerical experimentation demonstrates this rapid approach is due to massive dark matter haloes surrounding both Andromeda and our own Milky Way, but this mass does not slow down somewhat more distant galaxies because its effects are counteracted by more distant dark matter which lies in a vast flattened sheet out to distances well beyond the neighboring galaxies considered.   more

Million–Solar-Mass Enigma Shows Traits of a Tiny Galaxy—But Its Inner Structure Defies Explanation more

More and more black holes are found orbiting a luminous massive stellar companion. The future of these systems holds a fundamental puzzle: once the companion star expands and begins to lose mass onto the black hole, will the interaction remain stable or will the black hole plunge into the star and destroy it from within? Using state-of-the-art computational models, a team led at MPA has identified a surprisingly simple rule: the interaction is stable as long as the distance between the black hole and the star remains larger than about ten times the radius of the Sun. The newly found separation threshold will play a key role in determining which systems survive to form gravitational-wave sources and will help interpret the growing population of LIGO/Virgo/Kagra detections. Binaries that fail to remain stable, however, are no less remarkable. Such black hole-star mergers could be the explanation for luminous fast blue optical transients, linking these rare and powerful explosions to the violent end states of binary evolution. more

For her excellent graduate studies, Claude Cournoyer-Cloutier, who is now a postdoctoral fellow at the Max Planck Institute for Astrophysics, received the Governor General’s Academic Gold Medal at the McMaster University in Hamilton, Canada at the end of November. more

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