• Comment |

    The historic launch of the first several hundred out of 12,000 planned Starlink satellites heralds the arrival of the era of ultra-large satellite constellations. If it will bring new opportunities or insurmountable challenges to astronomy will probably depend on whether you are conducting your observations in space or from the surface of the Earth.

    • Igor Levchenko
    • , Shuyan Xu
    • , Yue-Liang Wu
    •  & Kateryna Bazaka
  • Comment |

    eROSITA, a new X-ray telescope currently performing an all-sky survey of unprecedented depth, aims to provide insights into dark energy, dark matter, black holes and perhaps new phenomena that have so far been invisible.

    • Andrea Merloni
    • , Kirpal Nandra
    •  & Peter Predehl
  • Comment |

    The Spitzer Space Telescope returned infrared images and spectra with unprecedented sensitivity and resolution, enabling the characterization of the dust-enshrouded star formation of and within galaxies. This has yielded indicators of total star formation, used as unbiased tracers of the stellar production across cosmic times.

    • Daniela Calzetti
  • Comment |

    A recent national survey on behalf of the French Society of Astronomy and Astrophysics highlights the elitism and gender discrimination faced by women — particularly women educated in universities rather than grandes écoles — when applying for permanent positions in astronomy in France.

    • Olivier Berné
    •  & Alexia Hilaire
  • Comment |

    The support of the international astronomical community to the 2030 Agenda for Sustainable Development is fundamental to advance the rights and needs of the most vulnerable groups of our global society. Among these groups are the refugees.

    • Sandra Benítez Herrera
    •  & Jorge Rivero González
  • Comment |

    Growing evidence suggests that synchrotron radiation plays a significant role in shaping the spectra of most γ-ray bursts. The relativistic jets producing them are likely to carry a significant fraction of energy in the form of a Poynting flux.

    • Bing Zhang
  • Comment |

    The recent disclosure regarding possible biological consequences of the Beresheet hard landing on the Moon raises concerns relating to planetary protection policies. Here we analyse legal and regulatory aspects of the landing of tardigrades and other biological material on the Moon and suggest possible ways to manage challenges arising therefrom.

    • Keren Shahar
    •  & Dov Greenbaum
  • Comment |

    Soon after Einstein’s calculation of the effect of the Sun’s gravitational field on the propagation of light in 1911, astronomers around the world tried to measure and verify the value. If the first attempts in Brazil in 1912 or Imperial Russia in 1914 had been successful, they would have proven Einstein wrong.

    • Luís C. B. Crispino
    •  & Santiago Paolantonio
  • Comment |

    Black hole feeding and feedback are often studied disjointly in both observations and simulations. We encourage the adoption of three physically motivated scales, linking them in a tight multiphase self-regulated loop. We pinpoint the key open questions of this unification problem and advocate for a multiwavelength, multiscale and interdisciplinary community.

    • Massimo Gaspari
    • , Francesco Tombesi
    •  & Massimo Cappi
  • Comment |

    The fundamental aim of inclusive astronomy is to bring astronomy to diverse groups of people while at the same time broadening the viewpoints of astronomy communicators. Building domestic and international networks is essential to disseminate inclusive activities and resources.

    • Kumiko Usuda-Sato
    • , Shin Mineshige
    •  & Lina Canas
  • Comment |

    The struggles of marginalized students, mentees and peers in astronomy and physics can be amplified by negative ‘fixed’ mindsets. Here are ways we can address mindset in our labs, our classrooms and ourselves.

    • Adam J. Burgasser
  • Comment |

    Astronomy across world cultures is rooted in indigenous knowledge. We share models of partnering with indigenous communities involving collaboration with integrity to co-create an inclusive scientific enterprise on Earth and in space.

    • Aparna Venkatesan
    • , David Begay
    • , Adam J. Burgasser
    • , Isabel Hawkins
    • , Ka’iu Kimura
    • , Nancy Maryboy
    •  & Laura Peticolas
  • Comment |

    The International Astronomical Youth Camp has benefited thousands of lives during its 50 year history. We explore the pedagogy behind this success, review a survey taken by more than 300 previous participants and discuss some of the challenges the camp faces in the future.

    • Hannah S. Dalgleish
    •  & Joshua L. Veitch-Michaelis
  • Comment |

    Researchers are debating whether habitability is a binary concept or not. We propose that the habitability of environments is a continuum defined by a series of binary questions.

    • Charles S. Cockell
    • , Adam H. Stevens
    •  & R. Prescott
  • Comment |

    In 1919 scientists from rival nations collaborated to test predictions made by Albert Einstein’s general theory of relativity during a solar eclipse expedition.

    • Stephen Pompea
    •  & Pedro Russo
  • Comment |

    Machine learning and related methods will be crucial for automatically classifying transients as they happen in order to best allocate follow-up resources. Such techniques cannot be used off the shelf, but must be developed by the community as a whole.

    • Emille E. O. Ishida
  • Comment |

    Besides supernovae, few astrophysical processes can release close to 1051 erg of energy. A growing number of stellar outbursts are now recognized to have energy releases matching those of faint supernovae. These transients can be triggered by various mechanisms, and their discrimination is sometimes a tricky issue.

    • Andrea Pastorello
    •  & Morgan Fraser
  • Comment |

    We all benefit when astronomy, and other sciences, are deconstructed and re-imagined in a different light to create activities accessible to all, independent of age, nationality, socioeconomic status, location, educational level, or mental or physical ability.

    • Mario A. De Leo-Winkler
  • Comment |

    Astrobiologists hope to detect signs of life on ocean worlds such as Europa. But the major challenge will actually come if such detections are successful — how to prove they are real and not artefacts of contamination or exotic chemistry?

    • Ralph D. Lorenz
  • Comment |

    Although a major objective in Mars exploration is the search for life, there are many scenarios that could lead to the recovery of lifeless samples. What could lifeless samples tell us about Mars and its habitability?

    • Charles S. Cockell
    •  & Sean McMahon
  • 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
  • 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
  • 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
  • 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
  • Comment |

    The existence of Earth’s Trojan asteroids is not well constrained and represents a major gap in our inventory of small bodies in near-Earth space. Their discovery would be of high scientific and human interest.

    • Renu Malhotra
  • Comment |

    Scientific outreach involving people with disabilities does not require specific techniques for specific conditions. An inclusive approach involving complementary senses not only helps those with disabilities but everyone else as well.

    • Enrique Pérez-Montero
  • Comment |

    Canadian astronomers and facilities have had a significant impact in wide-field astronomy. With community planning exercises underway this looks set to continue, with new capabilities and international collaborations in the near future.

    • Alan W. McConnachie
    • , Daryl Haggard
    • , Renée Hložek
    • , Will J. Percival
    •  & Michael Balogh
  • Comment |

    The surface of Mars has been well mapped and characterized, yet the subsurface — the most likely place to find signs of extant or extinct life and a repository of useful resources for human exploration — remains unexplored. In the near future this is set to change.

    • V. Stamenković
    • , L. W. Beegle
    • , K. Zacny
    • , D. D. Arumugam
    • , P. Baglioni
    • , N. Barba
    • , J. Baross
    • , M. S. Bell
    • , R. Bhartia
    • , J. G. Blank
    • , P. J. Boston
    • , D. Breuer
    • , W. Brinckerhoff
    • , M. S. Burgin
    • , I. Cooper
    • , V. Cormarkovic
    • , A. Davila
    • , R. M. Davis
    • , C. Edwards
    • , G. Etiope
    • , W. W. Fischer
    • , D. P. Glavin
    • , R. E. Grimm
    • , F. Inagaki
    • , J. L. Kirschvink
    • , A. Kobayashi
    • , T. Komarek
    • , M. Malaska
    • , J. Michalski
    • , B. Ménez
    • , M. Mischna
    • , D. Moser
    • , J. Mustard
    • , T. C. Onstott
    • , V. J. Orphan
    • , M. R. Osburn
    • , J. Plaut
    • , A.-C. Plesa
    • , N. Putzig
    • , K. L. Rogers
    • , L. Rothschild
    • , M. Russell
    • , H. Sapers
    • , B. Sherwood Lollar
    • , T. Spohn
    • , J. D. Tarnas
    • , M. Tuite
    • , D. Viola
    • , L. M. Ward
    • , B. Wilcox
    •  & R. Woolley
  • Comment |

    The masses of supermassive black holes, key to many cosmological studies, are highly uncertain beyond our local Universe. The main challenge is to establish the spatial and kinematic structure of the broad-line emitting gas in active galactic nuclei.

    • Marianne Vestergaard
  • Comment |

    The detection of a gravitational-wave background at nanohertz frequencies can tell us if and how supermassive black holes merge, and inform our knowledge of galaxy merger rates and supermassive black hole masses. All we have to do is time pulsars.

    • Chiara M. F. Mingarelli
  • Comment |

    Intermediate-mass black holes (BHs) in local dwarf galaxies are considered the relics of the early seed BHs. However, their growth might have been impacted by galaxy mergers and BH feedback so that they cannot be treated as tracers of the early seed BH population.

    • Mar Mezcua
  • Comment |

    There are efforts to establish a modern astronomical observatory on Timor Island, East Nusa Tenggara in Indonesia. This future observatory aims to answer fundamental astronomical questions and to strengthen the nation through education, research, science and technology.

    • Emanuel Sungging Mumpuni
    • , Lucky Puspitarini
    • , Rhorom Priyatikanto
    • , Clara Y. Yatini
    •  & Mahasena Putra
  • Comment |

    The field of gamma-ray burst astronomy arguably went through three decades of growing pains before reaching maturity. What development lessons can be learned for the adolescent field of fast radio burst astronomy?

    • S. R. Kulkarni
  • Comment |

    Fast radio bursts were discovered just over a decade ago, and their origin remains a mystery. Despite this disadvantage, astronomers have been using them to investigate the matter through which their bright, impulsive radiation travels.

    • Jean-Pierre Macquart
  • Comment |

    To date, one repeating and many apparently non-repeating fast radio bursts have been detected. This dichotomy has driven discussions about whether fast radio bursts stem from a single population of sources or two or more different populations. Here we present the arguments for and against.

    • Manisha Caleb
    • , Laura G. Spitler
    •  & Ben W. Stappers
  • Comment |

    Physical constraints on the sources of fast radio bursts are few, and therefore viable theoretical models are many. However, no one model can match all the available observational characteristics, meaning that these radio bursts remain one of the most mysterious phenomena in astrophysics.

    • Ue-Li Pen
  • Comment |

    Multi-wavelength and multi-messenger astronomy will reveal the phenomena that produce fast radio bursts, turning fast radio bursts into sharper tools with which to probe extragalactic plasma.

    • Sarah Burke-Spolaor
  • Comment |

    The detection of biosignatures on extrasolar planets would allow us to explore the predictability of evolution. What could we learn without directly obtaining a sample of life?

    • Charles S. Cockell
  • Comment |

    The National Astronomical Observatory of Japan has been working to increase public familiarity with astronomy. Here we introduce our outreach activities, including the development of interactive tools that make NAOJ data visible to the public.

    • Kumiko Usuda-Sato
    • , Hiroko Tsuzuki
    •  & Hitoshi Yamaoka
  • Comment |

    Understanding how and why star formation turns off in massive galaxies is a major challenge for studies of galaxy evolution. Many theoretical explanations have been proposed, but a definitive consensus is yet to be reached.

    • Allison Man
    •  & Sirio Belli
  • Comment |

    The next-generation observatory Lynx will provide an unprecedented X-ray view of the otherwise invisible Universe, directly observing the dawn of supermassive black holes, revealing the drivers of galaxy formation, tracing stellar activity including effects on planet habitability, and transforming our knowledge of the endpoints of stellar evolution.

    • Feryal Özel
  • Comment |

    LUVOIR is a concept for a powerful, flexible space observatory to enable the first survey for exoplanets most similar to the Earth, search for signs of life in our Solar System and beyond, and revolutionize astrophysics in the twenty-first century.

    • Aki Roberge
    •  & Leonidas A. Moustakas
  • Comment |

    The Habitable Exoplanet Observatory (HabEx) is a conceptual space-based 4-m telescope with the means to image and characterize potentially habitable planets orbiting Sun-like stars, and with ultraviolet to near-infrared imaging and spectroscopic capabilities suited to general observatory science.

    • B. Scott Gaudi
    • , Sara Seager
    • , Bertrand Mennesson
    • , Alina Kiessling
    • , Keith R. Warfield
    • , Kerri Cahoy
    • , John T. Clarke
    • , Shawn Domagal-Goldman
    • , Lee Feinberg
    • , Olivier Guyon
    • , N. Jeremy Kasdin
    • , Dimitri Mawet
    • , Peter Plavchan
    • , Tyler Robinson
    • , Leslie Rogers
    • , Paul Scowen
    • , Rachel Somerville
    • , Karl Stapelfeldt
    • , Chris Stark
    • , Daniel Stern
    •  & Margaret Turnbull
  • Comment |

    The Origins Space Telescope, one of four large Mission Concept Studies sponsored by NASA for review in the 2020 US Astrophysics Decadal Survey, will open unprecedented discovery space in the infrared, unveiling our cosmic origins.

    • Cara Battersby
    • , Lee Armus
    • , Edwin Bergin
    • , Tiffany Kataria
    • , Margaret Meixner
    • , Alexandra Pope
    • , Kevin B. Stevenson
    • , Asantha Cooray
    • , David Leisawitz
    • , Douglas Scott
    • , James Bauer
    • , C. Matt Bradford
    • , Kimberly Ennico
    • , Jonathan J. Fortney
    • , Lisa Kaltenegger
    • , Gary J. Melnick
    • , Stefanie N. Milam
    • , Desika Narayanan
    • , Deborah Padgett
    • , Klaus Pontoppidan
    • , Thomas Roellig
    • , Karin Sandstrom
    • , Kate Y. L. Su
    • , Joaquin Vieira
    • , Edward Wright
    • , Jonas Zmuidzinas
    • , Johannes Staguhn
    • , Kartik Sheth
    • , Dominic Benford
    • , Eric E. Mamajek
    • , Susan G. Neff
    • , Sean Carey
    • , Denis Burgarella
    • , Elvire De Beck
    • , Maryvonne Gerin
    • , Frank P. Helmich
    • , S. Harvey Moseley
    • , Itsuki Sakon
    •  & Martina C. Wiedner