Reviews & Analysis

The discovery of giant X-ray bubbles above and below the centre of the Milky Way confirms that the central supermassive black hole was once more than 100 million times brighter than its current state.

This Review Article summarizes our current understanding of ionized outflows in active galactic nuclei, observed in absorption in the ultraviolet and X-ray wavelengths, including the most relevant observations as well as their origin and acceleration mechanisms.

The commercial development of small satellites provides a unique opportunity to the astronomical community to overcome terrestrial limitations such as geography, atmosphere and planetary motion at a fraction of the cost of traditional space-based astronomy missions.

Recently, nanosatellite capabilities, driven by commercial and scientific innovation, have led to the development of high-performance satellite payloads and subsystems. This article reflects on the history, current state and future of the field.

In the context of near-Earth space becoming increasingly privatized and crowded due to the launch of satellite constellations, space must be viewed as an ancestral global commons that contains the heritage and future of humanity’s scientific and cultural practices.

The number of small satellites has grown hugely in the past decade, from tens of satellites per year in the mid-2010s to a projection of tens of thousands in orbit by the mid-2020s. This presents both problems and opportunities for observational astronomy. Small satellites offer complementary cost-effective capabilities to both ground-based astronomy and larger space missions. Compared with ground-based astronomy, these advantages are not just in the accessibility of wavelength ranges where the Earth’s atmosphere is opaque, but also in stable, high-precision photometry, long-term monitoring and improved areal coverage. Astronomy has a long history of new observational parameter spaces leading to major discoveries. Here we discuss the potential for small satellites to explore new parameter spaces in astrophysics, drawing on examples from current and proposed missions, and spanning a wide range of science goals from binary stars, exoplanets and Solar System science to the early Universe and fundamental physics.

Radio observations from the Low Frequency Radio Array suggest that magnetic fields in high-redshift clusters are of similar strength as their local counterparts. This finding implies that magnetic fields evolve differently than predicted by cosmological simulations.

On a magnetar’s surface, magnetic fields can create permanent sunspot-like structures. Accounting for heat diffusion and magnetic evolution in a magnetar’s crust in the latest simulations improves agreement with observations.

Comparing microphysical models of aerosol production to Hubble Space Telescope transit spectra reveals a surprisingly simple transition between atmospheres with hydrocarbon hazes, silicate clouds and clear skies.

In the Spitzer Space Telescope’s 16 years of operation, it observed many Solar System objects and environments. In this first Review Article of a pair, Spitzer’s insights into comets, centaurs and Kuiper belt objects—all remnants of the Solar System’s formation—are summarized.

In the Spitzer Space Telescope’s 16 years of operation, it observed many Solar System objects and environments. In this second Review Article of a pair, Spitzer’s insight into asteroids, dust clouds and rings and the ice giant planets are summarized.

A starburst galaxy from the peak epoch of cosmic star-formation history is found to have a significant ionizing ultraviolet emission. This finding will help better constrain the process of reionization in the early Universe.

The European Astronomical Society awarded its most prestigious prizes during its annual meeting held from 29 June to 3 July 2020. The meeting was entirely virtual and the largest such gathering of astrophysicists so far.

The Hayabusa2 and OSIRIS-REx teams have unexpectedly found bright boulders on their respective dark asteroids, Ryugu and Bennu, which provide solid clues about the composition and origin of impacting bodies in their formation history.

The upper atmospheres of all the giant planets are hotter than models predict. Analysis of Cassini Grand Finale observations of Saturn provide evidence that heat generated by the aurora is responsible.

Australian astronomers generate more greenhouse emissions than the average Australian citizen, thereby exacerbating the climate crisis. By quantifying contributions from different activities such as supercomputing and air travel, as presented here, astronomers can focus on reducing emissions by changing their practices in the most critical areas.

The annual Fast Radio Burst conference was held as an entirely virtual event on 6–9 July inclusive, with talks spread over three time zones and an online communication channel for discussions.

A periodic gamma-ray signal detected from the micro-quasar SS 433 cannot be associated with its jet. Instead, a new mechanism capable of channelling most of SS 433’s kinetic power to large distances is needed to explain the observations.

A Galactic wind blowing from the Milky Way nucleus has swept up a few hundred clouds of atomic gas. New observations reveal dense molecular cores in two of these clouds, indicating a high loss rate of interstellar gas from the Galactic centre.

Far-infrared polarimetric observations reveal the small-scale magnetic field structure within dense gas filaments. Gravity-induced gas flows in filaments supports a scenario in which gravitational collapse and star cluster formation occur even in the presence of relatively strong magnetic fields.