Articles in 2019

The global geological map of Saturn’s moon Titan, created using radar observations from Cassini, shows a clear latitudinal dependence, with young dune fields dominant at the equator, plains at mid-latitudes and lakes and old dissected terrains at the poles. Titan’s geomorphology is controlled mostly by climate and topography.

A pair of seminal papers developed key numerical methods and made the first predictions for the non-linear evolution of cold dark matter, ushering in the era of hierarchical cosmology and modern computational galaxy formation.

Every 10 years, X-ray astronomers gather in Bologna, Italy, to review the state of the field. After 30 years of these meetings, is there really still a separate field of X-ray astronomy?

The China Square Kilometre Array (SKA) team recently completed the first SKA regional centre prototype, marking an important leap forward towards a future large-scale deployment, explain Tao An, Xiang-Ping Wu and Xiaoyu Hong.

As Nature turns 150, we look back on its close connection to the Nobel Prize in Physics and some of the most epoch-defining papers in astronomy.

After 41 years of travel, the Voyager 2 spacecraft joins its twin in interstellar space. A suite of papers report Voyager 2’s experience of its transition through the heliosheath and heliopause to what lies beyond.

On its departure from the heliosphere, the plasma experiment on Voyager 2 observed changes corresponding to a 1.5-au-wide boundary region, followed by a much thinner boundary layer, before reaching the heliopause. Outside the heliopause, the very local interstellar medium is found to be hotter than expected. [The summary that originally appeared was incorrect and has been updated.]

This paper reports measurements of the magnetic fields and energetic particles detected by the Voyager 2 spacecraft as it passed from the heliosphere, through the heliosheath and heliopause, to the interstellar medium. As predicted by models, Voyager 2 encountered a ‘magnetic barrier’ before reaching the heliopause.

This Article reports measurements from the plasma wave instruments of the Voyager spacecraft as they passed from the heliosphere into interstellar space. The Voyager 2 instrument recorded an electron density jump of a factor of 20, similar to that from Voyager 1 several years previously.

As it crossed the heliopause, Voyager 2 observed a sharp decrease in measurements of the low-energy ions that originate within the heliosphere, and an increase in the cosmic rays from the Milky Way, without any of the precursor flux tubes that Voyager 1 experienced. Outside the heliopause, a boundary layer exists.

Measurements of energetic ions and electrons with the Low-Energy Charged Particle instrument on Voyager 2 are presented from the boundary of the heliosphere and from the interstellar medium. Voyager 2’s heliopause crossing bears some similarity to that of Voyager 1, despite differing solar wind conditions.

The standard cosmological model assumes a flat Universe, but some model inconsistencies appear when curvature is allowed, as supported by the latest Planck Legacy 2018 power spectra. Is it time to consider new physics?

The Crab Nebula, formed from a supernova recorded in 1054 ad, is the brightest object in the TeV (teraelectronvolt) gamma-ray sky. Measuring the extension of the gamma-ray nebula helps us to understand particle acceleration and interaction at the highest photon energies.

Accretion onto neutron stars can generate photon luminosities well in excess of the Eddington limit. Now it has been shown that it can also produce outflows with similar mechanical power, requiring a rethink of the interaction between accretion flows and neutron star magnetospheres.

An angular extension at gamma-ray energies of 52 arcseconds is detected for the Crab nebula, revealing the emission region of the highest-energy gamma rays; simulations of the electromagnetic emission provide a non-trivial test of our understanding of particle acceleration in the Crab nebula.