Volume 5

  • No. 12 December 2021

    Dwarf galaxies punching above their weight

    Despite their diminutive size (the Wolf–Lundmark–Melotte galaxy, pictured on the cover, is one tenth the size of the Milky Way), dwarf galaxies have emerged as key laboratories for studying open questions in several areas of astrophysics. This issue launches a Collection of short articles on dwarf galaxies, to which we will add both short and long pieces over time.

    See the Collection on dwarf galaxies

  • No. 11 November 2021

    The testing search for technosignatures

    Artist's impression of artificial lights on a hypothetical Earth-like planet in the Proxima Centauri system. Breakthrough Listen's search for technosignatures (signs of technology developed by extraterrestrial intelligence) scanned the Proxima Centauri system for artificial radio signals using the Parkes Telescope in Australia. Two papers in this issue of Nature Astronomy report the analysis of "BLC1", a candidate technosignature found in the data.

    See Price et al.

  • No. 10 October 2021

    Nearest radio galaxy tuned in

    Nearby Centaurus A contains a supermassive black hole that powers a jet of relativistic particles. Using the Event Horizon Telescope, Michael Janssen et al. image substructures down to the base of the jet, revealing a hollow bi-cone with extremely bright edges — much like the jet in the more massive M87.

    See Janssen et al.

  • No. 9 September 2021

    Super-stars go supernova

    At the end of their lives, so-called super-asymptotic giant branch stars of main sequence mass 8–10 solar masses are expected to explode via an electron-capture mechanism. Here Hiramatsu et al. identify a supernova that exhibits all six of their hallmarks of electron-capture supernovae.

    See Hiramatsu et al.

  • No. 8 August 2021

    Voyager 1 in the interstellar medium

    Voyager 1’s Plasma Wave System previously relied on coronal mass ejection-driven shock excitation of plasma to measure the density of the medium through which it was passing. However, as reported here, a very weak, narrowband, plasma oscillation has now been identified that enables the continuous measurement of the density of the interstellar medium beyond the heliosphere.

    See Ocker et al.

  • No. 7 July 2021

    Coronal dimmings as signatures of stellar ejections

    The image depicts coronal dimmings that occurred in association with a fast coronal mass ejection (CME) and X-class solar flare on 7 March 2012. The three-colour image combines observations at extreme-UV wavelengths by the Atmospheric Imaging Assembly (AIA), sensitive to different temperatures of the solar corona. Dark areas show the depletion of large regions of the corona due to the ejected CME plasma.

    See Veronig et al.

  • No. 6 June 2021

    Magnetic field properties in a galactic merger remnant

    Centaurus A is the remnant of a galactic merger that hosts an active galactic nucleus. Observations by the Stratospheric Observatory for Infrared Astronomy of its polarized light reveal a large-scale warped magnetic field that was probably generated from small-scale turbulent magnetic fields amplified through a dynamo process.

    See Lopez Rodriguez et al.

  • No. 5 May 2021

    New sources of neutrinos

    Observations of a high-energy neutrino led astronomers to identify a tidal disruption event as its likely source. The event was triggered by a star passing too close to a supermassive black hole. A mildly relativistic outflow was detected, confirming that the black hole can accelerate these cosmic particles.

    See Stein et al.

  • No. 4 April 2021

    The long and the short of turbulence

    The formation of stars through the collapse of molecular clouds is strongly influenced by turbulence. New high-resolution hydrodynamic simulations reveal the turbulent properties of the interstellar medium from subsonic to supersonic scales, in the process providing quantitative constraints for models of turbulent star formation.

    See Federrath et al.

  • No. 3 March 2021

    Subsurface ice on Mars

    The SWIM project maps the likelihood of finding water ice in the shallow subsurface of Mars, which could be used for future resource utilization. By putting together information from five different detection techniques, they identify the Arcadia Planitia and Deuteronilus Mensae regions as the most promising at mid-latitudes.

    See Morgan et al.

  • No. 2 February 2021

    Quantum sensor networks for exotic astrophysics

    Cataclysmic astrophysical events, such as black hole mergers, could release energy in unexpected forms. Emitted exotic low-mass fields would lag behind gravitational waves and cause feeble signals in quantum sensor networks, such as the atomic clocks comprising the GPS constellation.

    See Derevianko et al.

  • No. 1 January 2021

    Bright intruders

    The Hayabusa2 spacecraft has observed bright boulders on the surface of carbonaceous asteroid Ryugu. These boulders belong to a different body than Ryugu’s parent body and shed light on Ryugu’s collisional history. Similar bright boulders have been observed on asteroid Bennu by OSIRIS-REx.

    See Tatsumi et al.