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There is an ongoing debate as to whether ultra-diffuse galaxies are regular dwarf galaxies with low star formation or massive ‘failed’ objects that quenched their star formation in the early Universe. Current evidence seems to support the former scenario.
The Milky Way, Andromeda and Centaurus A host flattened arrangements of satellite dwarf galaxies with correlated kinematics. The rarity of similar structures in cosmological simulations constitutes a major problem for the ΛCDM model, with no obvious solution in sight.
The existence of planes of satellites has been a cosmological surprise. However, evidence for stable, long-lived satellite planes is generally tenuous, and they are unexpected in all current models of galaxy formation.
In the past 20 years, the discovery and characterization of the smallest galaxies have pushed the edges of observational endeavours and theoretical advancements alike, and they will continue to be at the forefront of this field for years to come.
Alongside its role in astronomical research, the newly commissioned 32-m radio telescope is being used as an outreach tool for astronomy education in Ghana. The observatory also serves as a facility for international postgraduate programmes.
Averting the imminent climate crisis requires large reductions in greenhouse gas emissions within this decade. To provide a benchmark for reduction and to identify the main sources, we estimate the carbon footprint of astronomy research in the Netherlands over 2019.
Although often not publicly identified, the personalities and life experiences of our referees affect their reviewing practices. Therefore having the most diverse set of reviewers possible underpins our efforts to ensure a fair peer review process.
Recent work has questioned whether nature can extract the rotational energy of a black hole via electromagnetic fields. Although we show that the Blandford–Znajek effect is sound, the deeper physics of the electric nature of black holes remains unresolved.
The question of the possibility of life beyond Earth, as framed by the Drake equation, can be quantified to show that habitable environments for life as we know it are commonplace in the Galaxy.