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Galaxies and clusters are the ensembles of stars and other astronomical objects bound together by gravitational forces. Galaxies are ordered into galaxy groups, which are in turn organised into clusters. The Earth is in a galaxy called the Milky Way, which is in the Local Group in the Virgo Supercluster.
Computer simulations based on the prevailing cosmological model, ΛCDM, reproduce many observed properties of our Universe. But a study of coherent satellite motions in galaxy clusters yields discrepancies that challenge the definition of ‘today’.
Decametre radio observations are challenging due to the presence of the ionosphere. Here Groeneveld et al. present a strategy to correct for the ionosphere that allows them to make sharp decametre radio images from the ground with the LOFAR telescope.
Ten stars in the Large Magellanic Cloud exhibit very low elemental abundances, suggesting that they have experienced enrichment by the earliest generations of stars only. These stars provide a window into a distant region of the high-redshift universe.
JWST detections of Si, C and Fe absorption lines in a bright z = 9.31 galaxy with a two-component clump structure suggest that mergers contributed to the rapid build-up of mass and chemical enrichment soon after the Big Bang.
Analysis of the JWST/NIRSpec spectrum of the recently observed Lyman-break galaxy JADES-GS+53.15508-27.80178 revealed a redshift of z = 7.3, a Balmer break and a complete absence of nebular emission lines, indicating that quenching occurred only 700 million years after the Big Bang.
An analysis of eight ultra-faint galaxies during the epoch of reionization with absolute magnitudes between −17 mag and −15 mag shows that most of the photons that reionized the Universe come from dwarf galaxies.
Computer simulations based on the prevailing cosmological model, ΛCDM, reproduce many observed properties of our Universe. But a study of coherent satellite motions in galaxy clusters yields discrepancies that challenge the definition of ‘today’.
Volker Springel created the original GADGET code more than 25 years ago. Now it supports some of the largest simulations in astrophysics, and is being developed to do vastly more.
The Lyman-α emission line of hydrogen should be absorbed and thus not seen from galaxies in the early Universe — and yet it is observed. Now detailed images from JWST coupled with magnetohydrodynamical simulations show that interactions between galaxies are facilitating the escape of this radiation.