Articles

Low-mass, low-metallicity cool subdwarf stars are rare in the solar neighbourhood, and therefore their properties are not well constrained observationally. Here the authors report both a mass and radius determination of a cool subdwarf in an eclipsing binary system, providing a valuable data point.

The abundance of primordial black holes in the Galactic halo is constrained through their microlensing of stars in M31. Despite monitoring tens of millions of stars, only a single candidate event is found, providing stringent upper bounds on their abundance.

A coupled thermal, geophysical and dynamical simulation covering 4.5 Gyr of evolution of Saturn’s inner mid-sized moons shows that, with the possible exception of Mimas, they formed early in Saturn’s history. A complex game of resonances has impacted the four older moons, shaping their geology and interior.

By conducting chemical reactions involving a single pair of reactants within helium nanodroplets, Henning and Krasnokutski have measured the energetics of simple reactions relevant to astrochemistry. This approach allows the reaction pathways of surface reactions to be predicted with more accuracy than before.

Ultracompact stellar clusters in the Galactic Centre are likely to be major contributors to the Galactic cosmic ray flux in the multi-TeV energy range. Observations of the diffuse gamma-ray emission from the Galactic Centre and two young massive star clusters correlate with the cosmic-ray distribution.

Bennu’s surface presents evidence of a variety of particle sizes, from fine regolith to metre-sized boulders. Its moderate thermal inertia suggests that the boulders are very porous or blanketed by thin dust. Bennu’s boulders exhibit high albedo variations, indicating different origins and/or ages.

Signatures of phyllosilicate-like hydrated minerals are widespread on Bennu’s surface, indicating significant aqueous alteration. The lack of spatial variations in the spectra down to the scale of ~100 m indicates both a relatively uniform particle size distribution and a lack of compositional segregation, possibly due to surficial redistribution processes.

Bennu’s surface has experienced continuous changes, mostly induced by its accelerating spin rate, which could have resulted in a collapse of its interior in the past. This scenario is also supported by the heterogeneity of Bennu’s internal mass distribution.

The iodine–xenon record in meteorites can be used to probe late-time processes within the Solar System, during the dissipation of its debris disk. Most primitive meteorites were processed and heated by impacts during this ~50 Myr period, rather than by the decay of ²⁶Al.

LOFAR radio observations, complemented by ultraviolet and visible light images, of the powerful class-X8.2 solar flare of 10 September 2017 pinpoint the location of multiple shock signatures of electron beams (herringbones) along the expanding coronal mass ejection.

A model of optical polarization provides a framework for studying the composition and dynamical evolution of the ejecta from the kilonova explosion accompanying the gravitational-wave event GW 170817, as well as future kilonovae.

Blue supergiant stars (BSGs) can undergo core collapse, resulting in a type II supernova explosion. Here, Tobias Fischer et al. identify a novel phase transition from nuclear matter to a quark–gluon plasma for particularly massive BSGs (>50 M_☉) that explains their explosion.

Small polycyclic aromatic hydrocarbons (PAHs) are thought to be nucleation sites for the growth of Titan’s haze layers. Using laboratory experiments and electronic structure calculations, Zhao et al. show that small PAHs can by synthesized by rapid, barrierless reactions in Titan’s low-temperature environments.

The James Webb Space Telescope may detect and distinguish a young galaxy that hosts a direct-collapse black hole and nearby massive metal-free star formation at redshift 15 with as little as a 20,000-second total exposure time across four filters.

The shock breakout (SBO) is the first electromagnetic signature of a supernova (SN) explosion. Förster et al. find that in nearly all type II SNe they survey that the SBO occurs on a timescale of days, indicating that the progenitors were surrounded by thick circumstellar matter when they exploded.

A 3D magnetohydrodynamic model forecasted the state of the solar corona during the eclipse that occurred on 21 August 2017, using observations taken ten days before the eclipse as boundary conditions. The agreement between the predicted images and those observed during the eclipse is very good.

An image-template analysis of eight years of Fermi-LAT data shows that the anomalous emission of gigaelectronvolt energies close to the centre of our Galaxy is better fitted with a boxy-shaped bulge generated by stars — possibly millisecond pulsars — than with a dark matter signal.

The MAVEN spacecraft observed brightening in the Lyman-α line correlated with solar wind activity, which can be attributed to auroral activity by solar wind protons interacting with the Martian neutral hydrogen corona. Proton aurorae are normally seen at Earth only.

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.

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.