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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.
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.
