Review Articles

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  • This article reviews the developments on the topic of so-called changing-look active galactic nuclei from the past ten years or so. These active galactic nuclei show dramatic flux and spectral changes at X-ray, ultraviolet and optical wavelengths, due to either obscuration or changes in accretion rate.

    • Claudio Ricci
    • Benny Trakhtenbrot
    Review Article
  • Continuous gravitational waves represent an exciting new frontier for multi-messenger astrophysics. This overview discusses their origins and the results obtained in the LIGO–Virgo–KAGRA O3 observing run, highlighting their potential for future studies.

    • B. Haskell
    • M. Bejger
    Review Article
  • Mars hosted hundreds of lakes, most of which formed earlier than 3.7 billion years ago and lasted only a limited amount of time. This overview of their characteristics and mineralogy highlights the importance of the Martian lakes as a record of ancient climate and potential for biogenesis.

    • Joseph R. Michalski
    • Timothy A. Goudge
    • Sarah Stewart Johnson
    Review Article
  • Light pollution is a growing problem affecting the night sky. This Review takes a comprehensive look at the factors contributing to elevated brightness at night, the measurement techniques and the ongoing assessment of sky quality.

    • John C. Barentine
    Review Article
  • A number of recent laboratory studies—summarized in this Review—have improved our understanding of the origin of presolar grains, with at least a quarter of presolar grains now being understood to originate in supernovae and their progenitors.

    • Peter Hoppe
    • Jan Leitner
    • Anthony P. Jones
    Review Article
  • This review summarizes our understanding of early-type dwarfs, which are the end-points of the evolution of low-mass galaxies. Their primeval stellar populations provide a unique laboratory for studying the physical conditions on small scales at epochs beyond z = 2.

    • Vasily Belokurov
    • N. Wyn Evans
    Review Article
  • Galaxies and their dark-matter haloes have posed several challenges to the dark energy plus cold dark matter (ΛCDM) cosmological model. This Review discusses the most notable challenges to ΛCDM regarding dwarf galaxies and the insights provided by recent cosmological numerical simulations.

    • Laura V. Sales
    • Andrew Wetzel
    • Azadeh Fattahi
    Review Article
  • This article reviews the properties of the dwarf galaxies of the Local Group from the point of view of their stellar dynamics and dark matter content and distribution, as inferred from the combination of observed data and dynamical models.

    • Giuseppina Battaglia
    • Carlo Nipoti
    Review Article
  • This Review looks at how the most recent results on intracluster light—the faint glow between galaxies within a galaxy cluster—fit into the current understanding of the field and provides a global perspective on the direction of future studies.

    • Mireia Montes
    Review Article
  • This Review summarizes what is known of the stellar and chemical properties of nearby (<20 Mpc) star-forming dwarf galaxies. These objects resemble the earliest formed galaxies and may thus represent a window on the distant, early Universe.

    • Francesca Annibali
    • Monica Tosi
    Review Article
  • 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.

    • Sibasish Laha
    • Christopher S. Reynolds
    • Daniel Proga
    Review Article
  • 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.

    • Carey Lisse
    • James Bauer
    • Charles Woodward
    Review Article
  • 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.

    • David E. Trilling
    • Carey Lisse
    • Anne Verbiscer
    Review Article
  • The Spitzer Space Telescope launched when the study of exoplanets was in its infancy, and yet it was remarkably successful in characterizing both exoplanet and brown dwarf systems through their mid-infrared emissions. This Review collates the highlights of Spitzer-based research in these fields.

    • Drake Deming
    • Heather A. Knutson
    Review Article