Browse Articles

  • Obituary |

    A pioneer of millimetre-wave astronomy, Norio Kaifu was an incomparable leader, person of spirit, colleague and friend.

    • Masahiko Hayashi
  • Editorial |

    The stunning picture of a black hole shadow that was released by the Event Horizon Telescope highlights the power of collaborative projects, as no single person, telescope or nation could have captured such an image.

  • News & Views |

    After 30 years of searching, the helium hydride ion, the first chemical bond that was formed in the Universe, has finally been detected outside the laboratory, in the interstellar medium. It was seen in planetary nebula NGC 7027 using the GREAT spectrometer aboard the Stratospheric Observatory for Infrared Astronomy.

    • Stephen Lepp
  • Mission Control |

    SCExAO is an instrument on the Subaru Telescope that is pushing the frontiers of what is possible with ground-based direct imaging of terrestrial exoplanets, explains Thayne Currie, on behalf of the SCExAO team.

    • Thayne Currie
  • News & Views |

    While the measurements of the Hubble constant from the local distance ladder and the cosmic microwave background radiation appear to disagree, given a sufficient number of localized detections, gravitational waves may possibly shed light on the tension.

    • Hsin-Yu Chen
  • Article |

    Leveraging the precision of K2 and TESS, Bowman et al. have detected variability in galactic and Magellanic blue supergiants that is due to low-frequency gravity waves in their interiors.

    • Dominic M. Bowman
    • , Siemen Burssens
    • , May G. Pedersen
    • , Cole Johnston
    • , Conny Aerts
    • , Bram Buysschaert
    • , Mathias Michielsen
    • , Andrew Tkachenko
    • , Tamara M. Rogers
    • , Philipp V. F. Edelmann
    • , Rathish P. Ratnasingam
    • , Sergio Simón-Díaz
    • , Norberto Castro
    • , Ehsan Moravveji
    • , Benjamin J. S. Pope
    • , Timothy R. White
    •  & Peter De Cat
  • Article |

    A predominance of small grains (tens of nanometres in size) over larger grains and the corresponding near- to mid-infrared excess radiation from H ii regions around massive stars and supernovae has been difficult to explain. Hoang et al. propose a radiative torque disruption method for large dust grains that fits with the observational constraints.

    • Thiem Hoang
    • , Le Ngoc Tram
    • , Hyeseung Lee
    •  & Sang-Hyeon Ahn
  • Comment |

    South Africa is looking forward to hosting the IAU General Assembly in 2024 — the first on the African continent. The meeting will come at a time of burgeoning scientific prosperity for the growing community of indigenous South African and African astronomers.

    • David A. H. Buckley
  • Review Article |

    This article reviews radio emission mechanisms in radio-quiet active galactic nuclei (AGNs), from star formation and AGN winds, to free-free emission from photoionized gas and AGN disk coronal activity. These mechanisms can be probed by sensitive radio observatories.

    • Francesca Panessa
    • , Ranieri Diego Baldi
    • , Ari Laor
    • , Paolo Padovani
    • , Ehud Behar
    •  & Ian McHardy
  • Letter |

    PlanetNet, a new deep learning algorithm, can quickly and accurately map spatial and spectral features across large, heterogeneous areas of a planet. The major components of the 2008 storm on Saturn are delineated, indicating regions to be probed more deeply with radiative transfer models.

    • I. P. Waldmann
    •  & C. A. Griffith
  • Article |

    A principal component analysis of Cassini’s infrared spectral maps of Titan reveals the main features of Titan’s equatorial surface, effectively removing the obscuring atmospheric effects. A 6,300-kilometre-long strip of exposed icy bedrock—uncorrelated with topography or measurements of the subsurface—is visible, surrounded by organic deposits.

    • Caitlin A. Griffith
    • , Paulo F. Penteado
    • , Jake D. Turner
    • , Catherine D. Neish
    • , Giuseppe Mitri
    • , Nicholas J. Montiel
    • , Ashley Schoenfeld
    •  & Rosaly M. C. Lopes
  • Letter |

    Carbon-rich and oxygen-rich material coexist in a presolar grain originated by an outburst of a CO nova and found within the LaPaz Icefield 031117 meteorite. Condensation of both carbon and oxygen can thus happen in the same circumstellar environment, contrary to previous assumptions.

    • Pierre Haenecour
    • , Jane Y. Howe
    • , Thomas J. Zega
    • , Sachiko Amari
    • , Katharina Lodders
    • , Jordi José
    • , Kazutoshi Kaji
    • , Takeshi Sunaoshi
    •  & Atsushi Muto
  • Letter |

    The Milky Way is thought to have accreted dwarf galaxies and their stellar content. Here, Xing et al. study a Galactic halo star enhanced in r-process elements and depleted in α-elements, indicating that it likely formed in a recently accreted dwarf galaxy similar to Ursa Minor.

    • Qian-Fan Xing
    • , Gang Zhao
    • , Wako Aoki
    • , Satoshi Honda
    • , Hai-Ning Li
    • , Miho N. Ishigaki
    •  & Tadafumi Matsuno
  • Article |

    Diurnal and seasonal temperature variations of comet 67P’s nucleus are monitored by Rosetta’s imaging spectrometer VIRTIS during two months in 2014. The nucleus appears thermally homogeneous, with the temperature fluctuations mainly controlled by self-heating and heliocentric distance.

    • F. Tosi
    • , F. Capaccioni
    • , M. T. Capria
    • , S. Mottola
    • , A. Zinzi
    • , M. Ciarniello
    • , G. Filacchione
    • , M. Hofstadter
    • , S. Fonti
    • , M. Formisano
    • , D. Kappel
    • , E. Kührt
    • , C. Leyrat
    • , J.-B. Vincent
    • , G. Arnold
    • , M. C. De Sanctis
    • , A. Longobardo
    • , E. Palomba
    • , A. Raponi
    • , B. Rousseau
    • , B. Schmitt
    • , M. A. Barucci
    • , G. Bellucci
    • , J. Benkhoff
    • , D. Bockelée-Morvan
    • , P. Cerroni
    • , J.-Ph. Combe
    • , D. Despan
    • , S. Erard
    • , F. Mancarella
    • , T. B. McCord
    • , A. Migliorini
    • , V. Orofino
    •  & G. Piccioni
  • News & Views |

    Measurement of the diffraction pattern of starlight during an asteroid occultation opens up new territory in stellar angular size determinations.

    • Gerard T. van Belle
  • Letter |

    Three mysterious features at Titan’s northern polar region appear as lakes when observed with Cassini’s radar during winter but as land when observed in the infrared during spring, providing evidence of liquid removal on Titan at seasonal scale.

    • Shannon M. MacKenzie
    • , Jason W. Barnes
    • , Jason D. Hofgartner
    • , Samuel P. D. Birch
    • , Matthew M. Hedman
    • , Antoine Lucas
    • , Sebastien Rodriguez
    • , Elizabeth P. Turtle
    •  & Christophe Sotin
  • Letter |

    Molecular emission lines originating in Titan’s relatively unexplored upper mesosphere and thermosphere reveal a strong prograde jet that reaches speeds of 340 m s–1 at 1,000 km altitude.

    • E. Lellouch
    • , M. A. Gurwell
    • , R. Moreno
    • , S. Vinatier
    • , D. F. Strobel
    • , A. Moullet
    • , B. Butler
    • , L. Lara
    • , T. Hidayat
    •  & E. Villard
  • Article |

    The composition and characteristics of a C-rich clast within the LaPaz Icefield 02342 meteorite suggests that the clast is composed of materials related to comets and icy bodies. The clast probably formed in the outer Solar System, was transported inward and finally accreted into LaPaz’s parent body.

    • Larry R. Nittler
    • , Rhonda M. Stroud
    • , Josep M. Trigo-Rodríguez
    • , Bradley T. De Gregorio
    • , Conel M. O’D. Alexander
    • , Jemma Davidson
    • , Carles E. Moyano-Cambero
    •  & Safoura Tanbakouei
  • Letter |

    Using large-aperture Cherenkov telescopes, Benbow et al. have measured the angular sizes of two stars through timely occultations by asteroids, achieving an order of magnitude improvement in resolution over the lunar occultation method.

    • W. Benbow
    • , R. Bird
    • , A. Brill
    • , R. Brose
    • , A. J. Chromey
    • , M. K. Daniel
    • , Q. Feng
    • , J. P. Finley
    • , L. Fortson
    • , A. Furniss
    • , G. H. Gillanders
    • , C. Giuri
    • , O. Gueta
    • , D. Hanna
    • , J. P. Halpern
    • , T. Hassan
    • , J. Holder
    • , G. Hughes
    • , T. B. Humensky
    • , A. M. Joyce
    • , P. Kaaret
    • , P. Kar
    • , N. Kelley-Hoskins
    • , M. Kertzman
    • , D. Kieda
    • , M. Krause
    • , M. J. Lang
    • , T. T. Y. Lin
    • , G. Maier
    • , N. Matthews
    • , P. Moriarty
    • , R. Mukherjee
    • , D. Nieto
    • , M. Nievas-Rosillo
    • , S. O’Brien
    • , R. A. Ong
    • , N. Park
    • , A. Petrashyk
    • , M. Pohl
    • , E. Pueschel
    • , J. Quinn
    • , K. Ragan
    • , P. T. Reynolds
    • , G. T. Richards
    • , E. Roache
    • , C. Rulten
    • , I. Sadeh
    • , M. Santander
    • , G. H. Sembroski
    • , K. Shahinyan
    • , I. Sushch
    • , S. P. Wakely
    • , R. M. Wells
    • , P. Wilcox
    • , A. Wilhelm
    • , D. A. Williams
    •  & T. J. Williamson
  • Article |

    Bathymetric radar measurements of several lacustrine features on Titan’s northern polar region were obtained during the last Cassini flyby in April 2017. These 100-m-deep and methane-dominated lakes are probably carved and replenished by local rainfall and regulated by subsurface flows.

    • M. Mastrogiuseppe
    • , V. Poggiali
    • , A. G. Hayes
    • , J. I. Lunine
    • , R. Seu
    • , G. Mitri
    •  & R. D. Lorenz
  • Article |

    Low-mass, low-metallicity cool subdwarf stars are rare in the solar neighbourhood, and therefore their properties are not well constrained observationally. Here the authors report both a mass and radius determination of a cool subdwarf in an eclipsing binary system, providing a valuable data point.

    • Alberto Rebassa-Mansergas
    • , Steven G. Parsons
    • , Vikram S. Dhillon
    • , Juanjuan Ren
    • , Stuart P. Littlefair
    • , Thomas R. Marsh
    •  & Santiago Torres
  • Letter |

    An intensification of the 7.8-µm methane emission at Jupiter’s poles is observed in coincidence with the arrival of a solar-wind compression in January 2017, highlighting the strong coupling between Jupiter’s magnetosphere and its neutral stratosphere.

    • J. A. Sinclair
    • , G. S. Orton
    • , J. Fernandes
    • , Y. Kasaba
    • , T. M. Sato
    • , T. Fujiyoshi
    • , C. Tao
    • , M. F. Vogt
    • , D. Grodent
    • , B. Bonfond
    • , J. I. Moses
    • , T. K. Greathouse
    • , W. Dunn
    • , R. S. Giles
    • , F. Tabataba-Vakili
    • , L. N. Fletcher
    •  & P. G. J. Irwin
  • Mission Control |

    The OSIRIS-REx mission has reached its target, asteroid Bennu, and is engaging in reconnaissance and early science observations in preparation for sample collection. Principal investigator team Heather Enos and Dante Lauretta provide an overview.

    • H. L. Enos
    •  & D. S. Lauretta
  • Comment |

    The new generation of sample return missions from small bodies will deliver to us fresh witnesses from the early Solar System. In-depth laboratory analysis of retrieved samples will allow us to look in unprecedented detail at the formation and evolution of organic materials in asteroids.

    • Rosario Brunetto
    •  & Cateline Lantz
  • Comment |

    On 27 June 2018 the Hayabusa2 spacecraft arrived at the carbonaceous asteroid Ryugu — a top-shaped asteroid with a very dark surface and many boulders. After a careful search for a safe and flat landing site, the first touchdown successfully took place on 22 February 2019.

    • Hikaru Yabuta
  • Comment |

    Japanese and US missions returning samples from the carbon-rich asteroids Ryugu and Bennu are the latest steps in probing our Solar System’s smallest bodies, near and far, for clues to our own origins and directions for our future exploration.

    • Richard P. Binzel
  • Comment |

    After the return of Hayabusa from asteroid Itokawa in 2010, the Japanese space agency JAXA developed a plan to investigate how our planet became habitable. The Hayabusa2 spacecraft mission to the asteroid Ryugu is just one part of this exploration that aims to track water and organics throughout our Solar System.

    • Masaki Fujimoto
    •  & Elizabeth J. Tasker
  • News & Views |

    In 1951, three separate research groups established radio astronomy as a contender to the dominance of optical astronomy. Using the interstellar 21-cm line, they provided a method to look deeper into our own Galaxy and back in time to the birth of all galaxies.

    • Emma Chapman
  • Editorial |

    NASA’s spacecraft OSIRIS-REx is planning to bring back a sample from a near-Earth asteroid in 2023, and it has just delivered its first scientific results. It is only one of the projects from various space agencies that will put small bodies and sample return into the spotlight in the upcoming decade.

  • Article |

    A coupled thermal, geophysical and dynamical simulation covering 4.5 Gyr of evolution of Saturn’s inner mid-sized moons shows that, with the possible exception of Mimas, they formed early in Saturn’s history. A complex game of resonances has impacted the four older moons, shaping their geology and interior.

    • Marc Neveu
    •  & Alyssa R. Rhoden
  • Letter |

    High-precision polarization observations of the binary star system Spica reveal that the amount of light from the primary component that is reflected off the secondary component (and vice versa) is a few per cent of the incident light. Such observations will be useful in identifying close binary systems.

    • Jeremy Bailey
    • , Daniel V. Cotton
    • , Lucyna Kedziora-Chudczer
    • , Ain De Horta
    •  & Darren Maybour
  • Article |

    The abundance of primordial black holes in the Galactic halo is constrained through their microlensing of stars in M31. Despite monitoring tens of millions of stars, only a single candidate event is found, providing stringent upper bounds on their abundance.

    • Hiroko Niikura
    • , Masahiro Takada
    • , Naoki Yasuda
    • , Robert H. Lupton
    • , Takahiro Sumi
    • , Surhud More
    • , Toshiki Kurita
    • , Sunao Sugiyama
    • , Anupreeta More
    • , Masamune Oguri
    •  & Masashi Chiba
  • Comment |

    Do black holes rotate, and if yes, how fast? This question is fundamental and has broad implications, but still remains open. There are significant observational challenges in current spin determinations, but future facilities offer prospects for precision measurements.

    • Ari Laor
  • Article |

    Ultracompact stellar clusters in the Galactic Centre are likely to be major contributors to the Galactic cosmic ray flux in the multi-TeV energy range. Observations of the diffuse gamma-ray emission from the Galactic Centre and two young massive star clusters correlate with the cosmic-ray distribution.

    • Felix Aharonian
    • , Ruizhi Yang
    •  & Emma de Oña Wilhelmi
  • Letter |

    There are three different evolutionary pathways leading to post-starburst galaxies in the EAGLE simulations, all consistent with observationally motivated scenarios. These multiple pathways explain the observational diversity of post-starburst galaxies.

    • M. M. Pawlik
    • , S. McAlpine
    • , J. W. Trayford
    • , V. Wild
    • , R. Bower
    • , R. A. Crain
    • , M. Schaller
    •  & J. Schaye
  • Article |

    By conducting chemical reactions involving a single pair of reactants within helium nanodroplets, Henning and Krasnokutski have measured the energetics of simple reactions relevant to astrochemistry. This approach allows the reaction pathways of surface reactions to be predicted with more accuracy than before.

    • Thomas K. Henning
    •  & Serge A. Krasnokutski
  • Comment |

    The PLOAD — Portuguese Language Office of Astronomy for Development — was established in 2015 by the International Astronomical Union (IAU) with the goal of promoting astronomy as a tool for sustainable development in Portuguese-speaking countries.

    • Alan Alves-Brito
    • , Patrícia F. Spinelli
    • , Valente A. Cuambe
    • , Ivanilda Cabral
    • , Joana Latas
    •  & Rosa Doran