Reviews & Analysis

After an initial period of activity, the formation of stars in the Galactic Centre has remained dormant for billions of years. The hibernation ended by a star-formation episode that could be due to the Milky Way interacting with other galaxies.

Cosmochemical measurements reveal the existence of two distinct reservoirs of non-carbonaceous and carbonaceous materials, originating from the inner and outer protoplanetary disk, respectively, which separated after the first million years after the birth of the Solar System, possibly due to the rapid growth of Jupiter’s core.

The Parker Solar Probe spacecraft completed the first two of its 24 scheduled orbits around the Sun on 18 June 2019, making history by flying halfway between Mercury and the Sun.

Volcanic and tectonic global maps of the inner planets and the Moon allow conclusions about the long-term volcanic behaviour of terrestrial planets and hint at the most promising extrasolar planets to look for active, radiogenically driven volcanism.

Years of dedicated efforts to tackle gender inequality in Europe show positive trends, but equality has not yet been achieved. This Perspective reports on the most recent initiatives in science and technology, with a special focus on the field of astronomy.

PhD bridge programmes provide an asset-based model to improve access and inclusion for students from underrepresented groups. Several well-known PhD bridge programmes in the United States are described and lessons learned from their experiences are discussed.

An overview of the nationwide programmes that are making an impact on diversity, culture and climate in Australia is presented, along with the most promising and innovative initiatives in Australian universities and institutions.

The convoluted challenges that stifle equity in academia can be understood in terms of dynamical systems descriptions of conflict developed in the social sciences, explaining the persistence of exclusive cultures and the inadequacy of simple fixes.

After George Gamow first proposed the idea of a hot Big Bang in 1948, it took 15 years for the burgeoning cosmology community to recognize his contribution for what it was.

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?

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.

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.

Seventy years after the first detection of interstellar magnetic fields, experts met in Newcastle upon Tyne, UK, on 10–14 June 2019, to discuss new perspectives on interstellar magnetic fields from small to large scales, from the Milky Way to distant galaxies and from observations to theories and simulations.

For years, much of our understanding of the formation of circumstellar aromatic molecules has been based on laboratory flame studies. Now, results acquired using a novel experimental technique suggest that circumstellar aromatics might not be formed under the conditions we thought they were.

Large-scale structures can probe the laws of gravity at scales that they have not yet been tested at, but these tests demand accurate modelling of complex galaxy formation processes in competing gravitational theories.

The peculiar carbon isotopic compositions of carbonates in the Tagish Lake meteorite suggest that D-type asteroids accreted in the outer part of the protoplanetary disk — beyond 10 au — before being dispersed sunwards to the main asteroid belt.

Present-day Mars is thought to be unsuitable for life as we know it. However, a thin coating of silica aerogel on the Martian surface may be enough to induce local, potentially habitable subsurface environments.

A Kavli Institute for Theoretical Physics workshop in July 2019 directed attention to the Hubble constant discrepancy. New results showed that it does not appear to depend on the use of any one method, team or source. Proposed solutions focused on the pre-recombination era.