Stellar News

Although dark matter makes up most of the matter in the universe, what it is made of remains one of the biggest open questions in physics. One indirect clue to its particle nature is how clumpy it is on small scales, such as in dwarf galaxies and smaller. The smallest of these clumps are associated with few or no stars and cannot be seen directly; however, their gravity can perturb stellar streams, thin trails of stars that act as sensitive probes. MPA scientists have now demonstrated that analysing both the location and the movement of stellar stream's stars can pinpoint the scale at which dark matter stops clumping several times more precisely, achieving a level of sensitivity comparable to the most advanced methods currently available. more

The IAU has announced the winners of its annual PhD prizes, including MPA postdoc Claude Cournoyer-Cloutier, who was recognised for her thesis on the 'Dynamics and Feedback of Massive Binaries in Young Massive Star Clusters'.
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Sun-like stars form within turbulent molecular clouds, encircled by disks of gas and dust - the birthplaces of planets. While the earliest phases of the disk assembly process are obscured by the surrounding dense gas, ALMA can observe proto-stellar disks shortly after their formation. In a project supported by the Excellence Cluster ORIGINS, researchers from MPA, MPE, Harvard, and the University of Cologne performed high-resolution non-ideal magneto-hydrodynamical simulations that self-consistently follow proto-stellar disk formation from their parental turbulent molecular clouds down to stellar scales, spanning over 10 orders of magnitude. The study uncovers the complex paths by which disks assemble and demonstrates that magnetic fields play a central role in their formation and early evolution.
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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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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

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

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.
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