Letters

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.

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.

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.

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.

A model of CO ice formation in protoplanetary disks shows that surface energy effects, such as the Kelvin effect, in ice nucleation and condensation must be considered to reproduce the observed distribution, abundances and evolution of gaseous CO.

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.

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.

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.

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.

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.

Spectroscopic and astrometric characterization of a quadruple star system composed of a pair of binary stars shows that the components will eventually merge to form white dwarfs, before potentially generating a sub-Chandrasekhar type Ia supernova.

Using a binary population synthesis model, the population of millisecond pulsars resulting from the accretion-induced collapse of O–Ne white dwarfs in the Galactic bulge is shown to reproduce characteristics of the Galactic Centre gamma-ray excess.

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.

Using asteroseismology to analyse 7,000 helium-burning red giants observed by NASA’s Kepler mission results in the separation of two classes of stars that must have undergone considerable mass loss, presumably due to stripping in binary interactions.

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.

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.

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.

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.

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.

The presence of a scalar charge around a small compact object during its final inspiral into a supermassive black hole could be detected by LISA, providing a way to test deviations from general relativity and the existence of new fields in nature.