A kink in the Keplerian flow of gas in a protoplanetary disk, observed in CO lines with ALMA, and a corresponding gap in the dust continuum emission, indicate the presence of an embedded massive planet within the gap. Therefore, some gaps, at least, are carved by orbiting planets.

See Pinte et al.

After 41 years of travel, Voyager 2 exited the heliosphere on 5 November 2018 at a distance of 119 au. This issue features five papers reporting plasma, particle and magnetic field measurements from the heliosheath, heliopause and interstellar medium, and their implications for our knowledge of the heliosphere.

See Krimigis et al., Burlaga et al., Stone et al., Richardson et al., Gurnett and Kurth, and News & Views by Strauss.

Just a few centimetres of silica aerogel can keep regions on Mars (pictured) above the melting point of water all year long and protect them from ultraviolet radiation. If deployed on areas with ice on the surface or subsurface, it can create a local habitat conducive to microorganism survival.

See Wordsworth et al. News & Views by Rivera-Valentín.

The ubiquitous population of Kuiper belt binaries holds clues to the mechanisms driving planetary formation. A 3D hydrodynamical model can reproduce the observed inclination distribution, as well as the dominance of prograde orbits, of Kuiper belt binaries by including planetesimal formation by the streaming instability.

See Nesvorný et al.

A snapshot from a hydrodynamical simulation of a three-solar-mass star, which shows gravity waves generated by turbulent core convection propagating throughout the star's interior. Gravity waves in stars can be observationally identified by space missions such as Kepler/K2 and TESS, which, when combined with asteroseismic modelling, provide key constraints on the physical properties of stellar interiors.

See Bowman et al.

The Rosetta mission obtained high-resolution temperature maps of the nucleus of comet 67P/Churyumov–Gerasimenko as it approached the Sun. The nucleus appears quite uniform, with observed temporal variations being driven by a shallow active layer at the surface, indicative of a pristine interior below depths of a few metres.

See Tosi et al.

Titan is the only known world beyond Earth with stable surface liquid bodies, composed of a mixture of hydrocarbons and concentrated in the northern polar region. Recent Cassini observations from the radar and the infrared spectrometry instruments (pictured overlaid) underscore the diversity of Titan’s lakes. They found shallow but spatially extended ponds that can form during winter and disappear in the space of a season, as well as 100-m-deep lakes created thousands of years ago by methane rain that replenishes them every year.

See MacKenzie et al.

A short burst of intense mass-loss near the end of a red giant’s life is known as a superwind — a picture increasingly at odds with observations. Now ALMA data reveal a spiral pattern in the outflow of two red giants, associated with binary interaction. Their companions gravitationally focus material, mimicking an intense superwind.

See Decin et al.

The OSIRIS-REx spacecraft has begun reconnoitring near-Earth asteroid Bennu. The first results unveil a global composition dominated by hydrated minerals, a diverse surface with an abundance of boulders and a shape indicative of continuous surficial change throughout its history.

See Scheeres et al.

The time series of the sunspot number — long used as a proxy for solar activity — covers more than 400 years of observations. However, earlier data suffer from temporal gaps and variable quality. These issues are taken into account in the creation of a way to visualize long-term solar variability.

See Muñoz-Jaramillo and Vaquero

A coherent history of the composition of Ceres’s surface from the conflicting information collected from different instruments on board the Dawn spacecraft is emerging: carbonaceous material, from impacts with other asteroids and/or from Ceres’s primordial composition, is mixed with products of widespread aqueous alteration events, such as clays and organics, producing a surface abundance of up to 20% carbon.

See Marchi et al.

Blazars, powered by an accreting supermassive black hole, launch collimated relativistic outflows (pictured) that are among the brightest persistent radiation sources in the Universe. The recent IceCube detection of a very-high-energy neutrino from the blazar TXS0506 + 056 in coincidence with a multi-wavelength flare implies that blazars can accelerate cosmic rays beyond petaelectronvolt energies, challenging conventional theoretical models.

See Gao et al. and News & Views by Pian