Articles

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.

Ground-based near-infrared spectra of Uranus detected hydrogen sulfide (H₂S) above the main cloud deck (at a pressure of 1.2–3 bar), suggesting that the bulk sulfur/nitrogen ratio in Uranus’s atmosphere exceeds unity and that the clouds are dominated by H₂S ice.

How does Titan’s thick brownish haze chemically evolve as it is transported from the upper atmosphere observed by Cassini to the lower regions sampled by Huygens? Laboratory vacuum ultraviolet experiments may explain the observed changes in nitrogen chemistry.

Titan's detached haze, a distinct layer on top of the main haze that provides a measure of the seasonal activity in the mesosphere, disappeared from 2012–2016, after equinox. Studying this transition will help us understand the dynamical and microphysical processes at work.

An individual star at z = 1.49 is gravitationally lensed and highly magnified by a foreground galaxy cluster. Fluctuations in the star’s emission provide insight on the mass function of intracluster stars, compact objects and the presence of dark-matter subhaloes.

Two unusual transient events, discovered by Hubble behind a strong-lensing galaxy cluster, can be explained as separate eruptions of a luminous blue variable star or a recurrent nova, or as an unrelated pair of stellar microlensing events.

Laboratory analyses on six carbonaceous chondrites suggest the presence of two water sources with different deuterium (D) enrichment levels in the protoplanetary disk: a D-poor inner reservoir and a D-rich water component transferred inward from the outer disk.

Pyrene, a polycyclic aromatic hydrocarbon composed of four fused benzene rings, is putatively a key molecule in the formation of 2D carbonaceous structures. Using experimental and computational techniques, Zhao et al. show that pyrene can form in circumstellar conditions.

A model for the non-thermal emission of pulsars can fit their γ- and X-ray spectra using just four physical parameters. The model explains several spectral features, and can be used to predict the detectability of pulsars in X-rays given the γ-ray emission, and vice versa.

The nuclear region of NGC 1097 is found to be dominated by non-thermal pressure. An anti-correlation between the star formation efficiency of molecular clouds and the magnetic field strength indicates that the formation of massive stars is quenched.

We calculate the continuous nanohertz gravitational-wave emission from individual supermassive black hole binaries and the gravitational-wave background they generate, which will be observable with pulsar timing arrays.

The authors present a photon detector suitable for terahertz astronomy, with very high sensitivity, low power consumption and the ability to be configured into arrays. This device is demonstrably able to count individual far-infrared photons.

The inner four planets of the TRAPPIST-1 system experienced induction heating due to magnetic interaction with their host star. This led them to experience increased volcanic activity, outgassing and potentially a subsurface magma ocean.

Experiments are presented that indicate that methane can be produced abiotically on Mars through the photocatalytic reaction of CO₂, in a process called methanogenesis. Methane can then be shocked (through impacts) to form RNA nucleobases and glycine.

By assessing the ionization fraction of the environment around Tycho’s (type Ia) supernova, the authors have constrained the properties of its progenitor enough to rule out a hot, luminous white dwarf. A double white dwarf binary merger is allowed.

A candidate dual supermassive black hole system with a projected separation of 0.35 pc is found in the gas-rich interacting spiral galaxy NGC 7674, evidenced by a ∼0.7 kpc Z-shaped radio jet and two, possibly inverted-spectrum, compact radio cores.

The authors present a spectrophotometric and hydrodynamical study of supernova OGLE-2014-SN-073, which had remarkably high inferred ejecta mass and energy, potentially higher than can be explained with canonical core-collapse neutrino-driven explosions.

Rotation of the Galactic bar at the centre of the Milky Way can explain gaps and asymmetries in stellar stream Palomar 5. Similar streams close to the Galactic Centre are therefore unfit for probing the dark matter subhalo interactions in our Galaxy.

A previously unidentified class of variable stars has been found in OGLE survey data, characterized by periodic brightness variations on ~30-min timescales, amplitudes of ~0.3 mag and temperatures of ~30,000 K. They are potentially evolved low-mass stars.

Ultrarelativistic photons and neutrinos from gamma-ray bursts offer a testbed for quantum gravity effects that would lead to an energy dependence of the travel times. A statistical analysis of astrophysical data shows that this behaviour may have been observed.