Articles

Using an atomic gas aggregation process in the laboratory to simulate the conditions in the inner regions of a carbon-rich evolved star, Martínez, Santoro, Merino and colleagues. show that aromatic species and fullerenes form surprisingly inefficiently, and that amorphous carbon nanograins and aliphatic clusters dominate.

A series of four storms appeared on Saturn’s northern polar region in 2018, unusually close to each other in space and time. By their dimension and the energy needed to form them, they appear to be a hitherto unobserved kind of storm at Saturn, intermediate between the regional- and the global-sized ones.

Graur et al. present near-infrared light curves of five type Ia supernovae based on Hubble Space Telescope data that show plateaux at late times (>150 days) rather than the expected ‘infrared catastrophe’. The authors suggest that the year-long plateaux are produced by the scattering of ultraviolet photons.

Asteroid families created by collisions in the last ~100 Myr have a higher fraction of subfamilies than older ones. The impact produces highly rotating fragments that generate such subfamilies by fission and subsequently disperse. The final appearance of an asteroid family is thus the product of a drawn-out evolution.

The range of sizes of old star clusters in the LMC does not necessarily imply the presence of binary black holes within them; the spread can be explained as a consequence of internal dynamical evolution and formation conditions. Looking at five old LMC clusters, Ferraro et al. find signs of dynamical youth.

An extensive survey to search for members of the only known Kuiper belt family, named after the parent body Haumea, found no family members fainter than absolute magnitude H_r = 7.9, significantly brighter than the detection limit (H_r = 9.5). This lack of small members is inconsistent with a catastrophic disruption as the origin of the Haumea family.

Radial velocity data of the young β Pictoris system acquired by HARPS and spanning 15 years show evidence of β Pic c, a gas giant of ~9 Jupiter masses orbiting on an eccentric orbit at ~2.4 au from the star, near the theoretical snowline. Both β Pic b and c, located close to the star, may have formed in situ by core accretion.

A glitch experienced by the Vela pulsar in 2016 has been studied in detail, revealing a curious slowdown of the neutron star’s rotation immediately before the event, and confirming some theoretical predictions of neutron-star physics.

The measured magnetic field strengths of four close-in gas giant planets are reported, using a technique based on magnetic star–planet interactions. Values range from 20 G to 120 G, close to estimates based on planetary internal heat flux, but ~10–100 times larger than predicted by dynamo scaling laws.

Full cosmological hydrodynamical simulations employing modified gravity find that disk galaxies can form and their stellar properties are only mildly affected. Modified gravity leaves signatures on large-scale structure observable with the Square Kilometre Array.

Tamanini and Danielski show that LISA will be sensitive enough to detect (massive) exoplanets orbiting double white-dwarf systems using gravitational waves. This population of exoplanets cannot be probed by other means, and detections will reveal potentially significant numbers of planets in the Galaxy and Magellanic Clouds.

Fragkou et al. present multiple pieces of evidence for the association of planetary nebula BMP J1613-5406 with Galactic open star cluster NGC 6067. Stars in the cluster evolve off the main sequence at about 5 solar masses, suggesting that this planetary nebula had a massive progenitor and supporting theoretical predictions of the mass range of planetary nebula progenitors.

A stacked series of lithographed polymer disks could provide a lightweight and modular optics system for a future hard X-ray telescope, retaining the angular resolution of current telescopes, but improving on effective area.

The velocity gradient technique is used to measure the magnetic field orientations and magnetization of five low-mass star-forming molecular clouds, also finding that collapsing regions constitute a small fraction of the volume in these clouds.

Leveraging the precision of K2 and TESS, Bowman et al. have detected variability in galactic and Magellanic blue supergiants that is due to low-frequency gravity waves in their interiors.

A predominance of small grains (tens of nanometres in size) over larger grains and the corresponding near- to mid-infrared excess radiation from H ii regions around massive stars and supernovae has been difficult to explain. Hoang et al. propose a radiative torque disruption method for large dust grains that fits with the observational constraints.

A principal component analysis of Cassini’s infrared spectral maps of Titan reveals the main features of Titan’s equatorial surface, effectively removing the obscuring atmospheric effects. A 6,300-kilometre-long strip of exposed icy bedrock—uncorrelated with topography or measurements of the subsurface—is visible, surrounded by organic deposits.

Stellar streams are the outstretched remnants of globular clusters torn apart by tidal forces. A data-driven search method for identifying streams finds stream material from ω Centauri, the most massive globular cluster within the Milky Way.

Diurnal and seasonal temperature variations of comet 67P’s nucleus are monitored by Rosetta’s imaging spectrometer VIRTIS during two months in 2014. The nucleus appears thermally homogeneous, with the temperature fluctuations mainly controlled by self-heating and heliocentric distance.

Bathymetric radar measurements of several lacustrine features on Titan’s northern polar region were obtained during the last Cassini flyby in April 2017. These 100-m-deep and methane-dominated lakes are probably carved and replenished by local rainfall and regulated by subsurface flows.