Articles

Methane ice has been presumed to form via the sequential hydrogenation of carbon atoms on dust grains for many years, but now Qasim et al. have performed the experiment, with and without the presence of water. Methane forms more rapidly in the polar ice phase.

Laboratory experiments show that the inclusion of even small quantities of sulfur in the atmospheres of exoplanets at 800 K significantly increases photochemical complexity, both in the vapour and in the solid phase: many sulfur gas products are created (including potential biosignature gases) and the production of organic haze particles increases threefold.

The European Southern Observatory trialled a distributed peer-review system—augmented by automated reviewer assignment—for its telescope time allocation process, finding that it worked as well as the standard process but resulted in a smaller burden on reviewers.

A magnetohydrodynamic model of the interaction between the solar wind and the interstellar medium shows that our heliosphere has a round shape, not a tail-like shape as usually assumed. The model reproduces the observations from Cassini, New Horizons and the two Voyager probes.

Parsons et al. calculate masses and radii for both members of a double white dwarf system, where the less-massive member is exhibiting non-radial g-mode pulsations, making it a prime target for asteroseismic analyses.

HD 74423 is an unusual binary star system containing two λ Boötis pulsators. TESS photometry reveals that one of the pair is pulsating along its tidal axis—but only in one hemisphere. Such an odd arrangement provides an interesting laboratory in which to study stellar pulsations and tidal distortion.

The combination of electromagnetic and gravitational-wave observations of binary neutron-star merger GW170817 with systematic sets of neutron-star equations of state has produced a tightly constrained radius of 11 km for a 1.4 M_⊙ neutron star. This constraint suggests that a neutron star–black hole merger is unlikely to produce an electromagnetic counterpart.

Radio observations of black hole MAXI J1820+070’s 2018 outburst captured an isolated radio flare that the authors connect with the launch of bipolar relativistic ejecta. Following the oncoming ejecta for more than half a year reveals that black hole jet energetics have been systematically underestimated.

Observations of the Faraday rotation towards pulsars in the halo globular cluster 47 Tucanae have been used to constrain the magnetic field strength in the Galactic halo, finding that it is unexpectedly strong.

Juno’s microwave radiometer data could measure the water concentration in the deep atmosphere of Jupiter (0.7 to 30 bar) at the equator: \(2.7^{+2.4}_{-1.7}\) times the solar O/H abundance, with a thermal vertical structure compatible with a moist adiabat.

A commonly held view is that presolar grains could not survive the high temperatures of the protoplanetary disk close to the Sun, where calcium–aluminium-rich inclusions (CAI) formed. Yet a detailed noble gas isotopic composition analysis of a CAI shows evidence of presolar SiC incorporated in it that could withstand high-temperature processing.

The pyrolysis experiments of the SAM instrument on board the Curiosity rover reconstruct the origin of organics at Gale crater. Some of them come from meteorites, but others have been formed in situ, with widespread past formation of carbonates via cryogenesis. More than 0.5 bar of CO₂ might have precipitated from the atmosphere.

A dust impact event detected by the ROSINA mass spectrometer towards the end of the Rosetta mission brings evidence of the presence of ammonium salts in comets. Ammonium salts can store enough nitrogen to explain the observed nitrogen depletion in comets and may have a role in amino acid formation.

Fragile et al. study the physics of accretion onto a neutron star from a thin accretion disk when interacting with an X-ray burst. A number of processes occur in the inner disk, including a reflexive retreat of the inner edge of the disk from the star, on the timescale of the burst.

Star DMPP-1 hosts a compact, four-planet system comprising three irradiated super-Earth-mass planets and one Neptune-mass planet, discovered through radial velocity measurements and the star’s anomalously low chromospheric emission.

This Article provides an overview of the Dispersed Matter Planet Project, a programme to discover close-in exoplanets being ablated by their host stars by means of the stars’ anomalously low chromospheric emission. One example is presented here: DMPP-2 hosts a sub-Jupiter-mass planet around a γ Doradus pulsator.

The third target of the Dispersed Matter Planet Project, DMPP-3, is an unusual binary system containing a solar-type star ablating a super-Earth-mass planet, along with a very low mass secondary.

Dust in the Solar System originates primarily in two locations: the interstellar medium and stellar outflows. On the basis of measurements of palladium isotopes in iron meteorites, Ek et al. suggest that the interstellar component was destroyed in the inner Solar System, revealing an enhancement of s-process isotopes from stardust.

Coupling a global surface hydrology model to an existing atmospheric model of Titan reproduces the observed variable climate and distribution of surface liquid, with possible implications for an unobserved methane reservoir on Titan.

The large-scale spatial distribution of local active galactic nuclei can constrain the black hole–stellar mass relation and their mean radiative efficiency to 10–20%, suggesting moderate to high spins for the vast majority of supermassive black holes.