Research articles

A model reconstructs the radiation dose from both protons and electrons on Europa’s surface. Using laboratory data on irradiated amino acids, it shows that organics can be preserved at detectable levels at depths of just a few centimetres at mid-to-high latitudes and in young (<10-Myr-old) terrains.

M31’s massive and metal-rich stellar halo appears to indicate that a single dominant merger with a large galaxy took place about 2 Gyr ago, co-temporal with M31’s global burst of star formation. M32 is likely to be the stripped core of the disrupted galaxy.

The X-ray-induced photodesorption of water from astrophysical ices, intact, has been little studied. However, it could be a key process in producing the cold water vapour that is seen in these regions. Here, the yield of such a mechanism is experimentally quantified.

Reconstructing matter density from the velocities of local galaxies in a linear manner is standard practice. Averaging over the density fields of an ensemble of nonlinear simulations reveals a stronger galaxy ‘bias’ than in the linear regime, providing insights into the distribution of dark matter and the formation of galaxies.

The strong gravitational lensing signal around the massive cluster PSZ2 G099.86+58.45 indicates environment matter density in notable excess of the cosmological mean and implies that enhancing mechanisms around high-mass halos can be very effective.

Late-time optical and near-infrared observations of the binary neutron star merger GW170817 are at odds with kilonova models but match a Gaussian-structured relativistic jet, which would have launched a high-luminosity short gamma-ray burst to an aligned observer.

All inner main-belt asteroids, and not just those belonging to a specific family as previously thought, originate from the splintering of a few large asteroids. The history of such precursors determines the compositional variety we observe in asteroids and meteorites.

Using high-resolution spectra, the CARMENES survey detects a hydrogen atmosphere around KELT-9b, the hottest exoplanet ever discovered. This hydrogen envelope almost entirely fills the Roche lobe, indicating intense atmospheric loss.

Massive binary star Eta Carinae drives the strongest colliding wind shock in the solar neighbourhood. Using NuSTAR and XMM-Newton data, Eta Car has now been convincingly shown to accelerate non-thermal particles, contributing to the Galactic cosmic ray flux.

A method of atmospheric retrieval for exoplanets that uses supervised ‘random forest’ machine learning, less time-consuming than standard techniques, is presented. Tests on Hubble spectra of WASP-12b give results consistent with standard atmospheric retrievals.

The X-ray polarization properties of the black hole binary Cygnus X-1 in its hard state, combined with spectral and timing data, reveals that the accretion disk corona is either an extended structure or located far from the black hole.

In simulations, young massive star clusters in the present-day Universe form naturally in giant molecular clouds, despite the influence of radiative feedback. The same process occurred in earlier epochs, for instance, when globular clusters were born.

Evidence for the earliest phase of planet formation, dust grain growth, has been seen in the very young and massive circumstellar disk around low-mass protostar TMC1A. Such systems, still rich in gas, are responsible for the high-mass end of the exoplanet mass distribution.

A bright X-ray outburst from a massive star cluster 12.5 kpc from a galactic centre fits the profile of a tidal disruption event (TDE), indicating the likely presence of an intermediate-mass black hole (IMBH). TDEs could be the most effective way of identifying IMBHs.

By studying the properties of almost 200 disk galaxies, it is shown that modified Newtonian dynamics (MOND), or MOND-like alternative theories of gravity based on the existence of a fundamental acceleration scale, are ruled out as fundamental theories for galaxies at more than 10σ.

The presence of nanodiamonds in protoplanetary disks correlates strongly with the detection of anomalous microwave emission from the same disks, implying that spinning nanodiamonds rather than polycyclic aromatic hydrocarbons are the source of this puzzling ~30 GHz emission feature.

The Waves instrument on board the Juno spacecraft has detected ~1,600 lightning strokes in roughly 1 year of close approaches to Jupiter, indicated by low-dispersion rapid whistlers much shorter than those detected by Voyager 1 in Io’s plasma torus.

Cassini magnetic field and plasma observations find evidence of magnetic reconnection on the dayside of Saturn’s magnetosphere, which can explain local auroral pulsations and play a role in the transport of energetic particles within rapidly rotating magnetospheres.

Images of 67P's nucleus from the Rosetta spacecraft, together with numerical simulations, show that the jet-like features of cometary comae can be produced by diffuse activity focused by the nucleus topography as well as non-uniform insolation over the surface.

The suite of small moons orbiting close to Saturn exhibits a variety of shapes that provide clues to moon formation processes. A model shows that all of these shapes can be obtained with a single mechanism: merging collisions among similar-sized moonlets.