An amendment to this paper has been published and can be accessed via a link at the top of the paper.

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.

On 3 May 2020 the Greek and extended international astronomy community lost Professor Emeritus John Hugh Seiradakis, a highly impactful, wide-reaching researcher and educator, and mentor to generations of students.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The oxygen emission at 557.7 nm is a ubiquitous component of the spectrum of the terrestrial polar aurora and the reason for its usual green colour1. It is also observed as a thin layer of glow surrounding the Earth near 90 km altitude in the dayside atmosphere2,3 but it has so far eluded detection in other planets. Here we report dayglow observations of the green line outside the Earth. They have

The space and planetary science community lost a great leader, Professor Weixing Wan, on 20 May 2020, aged 62. He was a world-leading space scientist and a pioneer in China’s planetary science programme.

On the anniversary of ROSAT’s launch, we reflect on the relevance and promise of X-ray observations in all fields of astronomy. Properly laying out a plan for the future of the field will allow it to continue flourishing.

No confirmed counterparts during LIGO and Virgo’s third observing run bring more questions than answers to the active multi-messenger community, which is adapting collaboratively and technically as expectations evolve and more data are taken.

The measure of Titan’s incredibly large migration speed away from Saturn reveals that tidal dissipation depends on the orbital frequency. This new paradigm has many implications for the internal structure of Saturn and the history of its satellite system.

Saturn is orbited by dozens of moons, and the intricate dynamics of this complex system provide clues about its formation and evolution. Tidal friction within Saturn causes its moons to migrate outwards, driving them into orbital resonances that pump their eccentricities or inclinations, which in turn leads to tidal heating of the moons. However, in giant planets, the dissipative processes that determine

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.

Key questions about ice on the red planet, its climate record and its potential for habitability were the subject of the seventh edition of the International Conference on Mars Polar Science and Exploration, held for the first time in the Southern Hemisphere.

For more than six decades, the quest to understand the formation of hot (about 20,000−30,000 K) extreme horizontal branch (EHB) stars in Galactic globular clusters has remained one of the most elusive in stellar evolutionary theory. Here we report on two discoveries that challenge the idea of the stable luminosity of EHB stars. The first mode of EHB variability is periodic and cannot be ascribed to

The discovery of four bright fast radio bursts with accurate localization on the sky and association with nearby galaxies enabled a statistical estimate of the baryon content in the intergalactic medium and intervening galaxy halos by measuring the amount of ionized gas towards these sources.

Satellites orbiting disk galaxies can induce phase space features such as spirality, vertical heating and phase-mixing in their disks. Such features have also been observed in our own Galaxy, but the complexity of the Milky Way disk has only recently been fully mapped by Gaia Data Release 2 (DR2) data. This complex behaviour is mainly ascribed to repeated perturbations induced by the Sagittarius dwarf

Magnetohydrodynamic turbulence is a ubiquitous and fundamental ingredient underlying many astrophysical phenomena. The multiphase nature of the interstellar medium and the diversity of driving mechanisms give rise to spatial variation of turbulence properties, particularly plasma properties. There has been no observational diagnosis of the plasma modes beyond the solar system so far. Here we report

Solar filaments, also called solar prominences when appearing above the solar limb, are cold, dense materials suspended in the hot tenuous solar corona, consisting of numerous long, fibril-like threads. These threads are the key to disclosing the physics of solar filaments. Similar structures also exist in galaxy clusters. Besides their mysterious formation, filament threads are observed to move with

Aerosols are common in the atmospheres of exoplanets across a wide swath of temperatures, masses and ages1,2,3. These aerosols strongly impact observations of transmitted, reflected and emitted light from exoplanets, obfuscating our understanding of exoplanet thermal structure and composition4,5,6. Knowing the dominant aerosol composition would facilitate interpretations of exoplanet observations and

Induced magnetospheres form around conductive non-magnetized planetary objects (such as the ionospheres of Mars, Venus, Titan, Pluto and comets) in the electrodynamic interaction with a magnetized flowing plasma, such as the solar wind. The resulting induced currents couple the ionosphere and the deflected plasma, thus they provide insight into the solar wind’s role in powering the heating, escape

The detection of a ring galaxy at a redshift of z = 2.2, potentially a product of a past collision with a companion galaxy, provides new insights on ring formation and the evolution of disk galaxies in the early Universe.

In the local (redshift z ≈ 0) Universe, collisional ring galaxies make up only ~0.01% of galaxies1 and are formed by head-on galactic collisions that trigger radially propagating density waves2,3,4. These striking systems provide key snapshots for dissecting galactic disks and are studied extensively in the local Universe5,6,7,8,9. However, not much is known about distant (z > 0.1) collisional rings10

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

We are living in exceptional circumstances. It is not business as usual. There is no script, and where we end up after the global pandemic is partly up to us.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Observations of extrasolar planets were not projected to be a substantial part of the Spitzer Space Telescope’s mission when it was conceived and designed. Nevertheless, Spitzer was the first facility to detect thermal emission from a hot Jupiter-sized planet, and the range of its exoplanetary investigations grew to encompass transiting planets, microlensing, brown dwarfs, and direct imaging searches

The cosmic origin of the heaviest elements in the periodic table remains a mystery. Estimates of the physical locations of element-producing events within small galaxies that formed in the early Universe are now providing new clues.

PolarLight is the first dedicated soft X-ray polarimeter in space since the 1970s and is attempting to reopen this long-awaited window in astronomy, explain Principal Investigator Hua Feng and Ronaldo Bellazzini.

Luminous and ultraluminous infrared galaxies have been an active area of galaxy research since their discovery more than three decades ago. With its vast increase in sensitivity in the infrared, Spitzer played a major role in exploring these galaxies in the local Universe, and at high redshifts. In this Review, we highlight some of the discoveries made with the Infrared Spectrograph on Spitzer, through

The Curiosity rover is unveiling the persistence of habitable environments more than three-billion years ago at Gale crater, Mars. New analyses of Gale’s ancient sediments show that chemical processing of organic material occurred on a liquid-water rich and freezing early Mars.

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.

When did galaxies start forming stars? What is the role of distant galaxies in galaxy formation models and the epoch of reionization? What are the conditions in typical star-forming galaxies at redshifts ≳4? Why is galaxy evolution dependent on environment? The Spitzer Space Telescope has been a crucial tool for addressing these questions. Accurate knowledge of stellar masses, ages and star formation

Measurements with a CubeSat gas pixel detector reveal a change in the Crab pulsar polarization after a glitch in the spin period, suggesting that starquakes alter the magnetosphere.

Accurately constraining the formation and evolution of the lunar magnesian suite is key to understanding the earliest periods of magmatic crustal building that followed accretion and primordial differentiation of the Moon. However, the origin and evolution of these unique rocks is highly debated. Here, we report on the microstructural characterization of a large (~250-μm) baddeleyite (monoclinic-ZrO2)

Special Regions on Mars are defined as environments able to host liquid water that simultaneously meets certain temperature and water activity requirements that allow known terrestrial organisms to replicate1,2 and therefore could be habitable. Such regions would be of concern for planetary protection policies owing to the potential for forward contamination (biological contamination from Earth). Pure

The Crab nebula is so far the only celestial object with a statistically significant detection in soft X-ray polarimetry1,2,3,4, a window that has not been explored in astronomy since the 1970s. However, soft X-ray polarimetry is expected to be a sensitive probe of magnetic fields in high-energy astrophysical objects, including rotation-powered pulsars5,6,7 and pulsar wind nebulae8. Here we report

In the event of accidental transmission of microbes to other planets, we must consider whether the local conditions would allow their proliferation. Whereas temperatures on Mars are usually hostile to life, liquid water is available from deliquescing salts.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Theory and observation for the search for life on exoplanets via atmospheric ‘biosignature gases’ is accelerating, motivated by the capabilities of the next generation of space- and ground-based telescopes. The most observationally accessible rocky planet atmospheres are those dominated by molecular hydrogen gas, because the low density of H2 gas leads to an expansive atmosphere. The capability of

Galaxy clusters are the most massive collapsed structures in the Universe, with potential wells filled with hot, X-ray-emitting intracluster medium (ICM). Observations, however, show that a substantial number of clusters (the so-called cool-core clusters) also contain large amounts of cold gas in their centres, some of which is in the form of spatially extended filaments spanning scales of tens of

Exoplanetary and Solar System science lost a major figure with the sudden passing of Professor Adam Showman on 16 March 2020 at the age of 51. He was recognized as the world’s leading authority in the field of atmospheric dynamics of exoplanets.

The Spitzer Space Telescope recently ceased operations, powering down its remaining detector after more than a decade and a half of revealing the infrared Universe. Its legacy will be continued by far more expensive missions that will have big boots to fill.