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  • Harnessing the power of citizen science and machine learning, this study takes in 20 years of Hubble Space Telescope images, of which 2.7% show satellite streaks, and predicts that this fraction will increase by up to an order of magnitude in the next decade.

    • Sandor Kruk
    • Pablo García-Martín
    • Mark J. McCaughrean
    LetterOpen Access
  • Data from the gravitational wave event GW190521 can be explained by a semi-analytical model of two stellar-mass, nonspinning black holes on highly eccentric, hyperbolic orbits that undergo two close encounters before merging into an intermediate-mass black hole.

    • R. Gamba
    • M. Breschi
    • A. Nagar
  • Early Martian surface and subsurface were probably habitable for methanogenic microorganisms with a hydrogen-based metabolism, according to an ecological model coupled with a geochemical simulation. Feedback effects of such a biosphere on the atmosphere might have driven strong global cooling.

    • Boris Sauterey
    • Benjamin Charnay
    • Régis Ferrière
  • Topographic signatures typical of subglacial lakes on Earth are observed over the south pole area of Mars, where MARSIS found possible signatures of similar bodies of water. Modelling shows that such signatures can be generated in 0.5–5 Myr, depending on the intensity of the geothermal heating.

    • N. S. Arnold
    • F. E. G. Butcher
    • M. R. Balme
  • Fast radio bursts (FRBs) can be used as sensitive probes of diffuse gas in galaxy dark-matter haloes. Here the authors analyse several fast radio bursts that intersect galaxy dark-matter haloes within 40 Mpc, finding that the additional dispersion provided by the diffuse gas (presumably the intragroup medium) is in excess of 90 pc cm−3.

    • Liam Connor
    • Vikram Ravi
  • In 1933, Fritz Zwicky's measurement of the Coma cluster's mass led him to infer the existence of dark matter. The present work applies a new deep learning approach to revisit Zwicky's original measurement and demonstrate the progress of modern astronomy.

    • Matthew Ho
    • Michelle Ntampaka
    • Hy Trac
  • In February 2020, Betelgeuse experienced a historical minimum that became known as the Great Dimming. A meteorological satellite with mid-infrared capabilities caught the event in its observations of the Earth, and these provide insights into the causes: a decrease in effective temperature coupled with dust formation.

    • Daisuke Taniguchi
    • Kazuya Yamazaki
    • Shinsuke Uno
    LetterOpen Access
  • The offset degeneracy in gravitational microlensing observations, found by analysing various microlensing events with an approach driven by machine learning, unifies previous mathematical degeneracies and points to a deeper symmetry in the mathematics of two-body lensing.

    • Keming Zhang
    • B. Scott Gaudi
    • Joshua S. Bloom
  • A unified theoretical framework for wind transport of grains and dune formation, which takes into account the various exotic conditions present across the Solar System, is presented. The results are consistent with experimental observations and give insight into the different behaviour of sediments and dunes in Solar System bodies.

    • Andrew Gunn
    • Douglas J. Jerolmack
  • Detection of the 2021 outburst of the nova RS Oph in very-high-energy gamma rays by the MAGIC telescopes is reported. Investigation of the gamma-ray emission provides evidence for acceleration of protons within the nova shock, which then propagate outwards to create bubbles of enhanced cosmic ray density.

    • V. A. Acciari
    • S. Ansoldi
    • P. Valisa
  • The seasonal colour variations of comet 67P’s nucleus observed in the visible wavelengths by the VIRTIS mapping spectrometer throughout the whole Rosetta mission are driven by the evolution of metre-scale water-enriched blocks homogeneously distributed across the nucleus, periodically exposed to sunlight by CO2 sublimation.

    • Mauro Ciarniello
    • Marco Fulle
    • Gabriele Arnold
  • Well-observed gamma-ray binary system LS I +61° 303 consists of a high-mass star and a compact object whose nature is unknown. Here, transient radio pulsations detected with the sensitive FAST telescope suggest that the compact object is a rotating neutron star.

    • Shan-Shan Weng
    • Lei Qian
    • Qi-Rong Yuan
  • Alkaline conditions in icy worlds favour aqueous alteration processes even at subzero temperatures. As a consequence of geologically rapid alterations, the rocky cores of all icy bodies larger than 500 km in diameter should be largely composed by altered hydrated minerals formed within a few hundred million years after formation.

    • Amber Zandanel
    • Roland Hellmann
    • Gabriel Tobie
  • Ultrahot giant planet WASP-121b has a stratosphere that warms up with altitude during the day and cools down with altitude during the night. This trend is in agreement with predictions from circulation models in chemical equilibrium. Efficient vertical mixing hinders condensation of at least some refractory materials.

    • Thomas Mikal-Evans
    • David K. Sing
    • Jessica J. Spake
    LetterOpen Access
  • The lunar samples brought back by the Chinese Chang’e-5 mission have an age of 2.030 ± 0.004 billion years, providing valuable new constraints on the cratering chronology used to date most Solar System surfaces. Here an updated chronology model is presented and compared with other models currently in use.

    • Zongyu Yue
    • Kaichang Di
    • Ziyuan Ouyang