Articles in 2020

The Almahata Sitta 202 meteorite fragment hosts evidence of aqueous alteration at intermediate pressures and temperatures, indicative of a hitherto unknown Ceres-sized parent body. Such intermediate conditions, also seen in the Allende meteorite, might have been more common than our biased meteorite collection indicates.

Pluto’s haze could have a major icy component created by the condensation of organic molecules such as C₄H₂. This is different from Titan whose haze, despite a similar atmospheric composition, is mostly macromolecular aggregates. Triton’s haze, instead, should be dominated by ices, particularly C₂H₄.

Flares from K and M dwarf stars drive change, and sustain an altered atmospheric chemistry, in orbiting rocky planets, according to a suite of three-dimensional climate models. The atmospheres of rocky planets around G dwarfs rapidly return to their pre-flare states, however.

A globular cluster-like system in the Galactic bulge hosts two stellar populations with remarkably different ages, identifying it as a site of recent star formation and providing observational proof for the hierarchical assembly of the Milky Way spheroid.

The detection of three ultraviolet emission lines from GN-z11 can be interpreted as the [C iii] λ1907, C iii] λ1909 doublet and O iii] λ1666 at z = 10.957 ± 0.001, confirming GN-z11 as the most distant galaxy known to date and revealing the properties of its dense ionized gas.

A peculiar near-infrared transient with an observed duration shorter than 245 s, coincident with the luminous star-forming galaxy GN-z11 at z ≈ 11, might have arisen from a rest-frame ultraviolet flash associated with a long gamma-ray burst in GN-z11.

The discovery of giant X-ray bubbles above and below the centre of the Milky Way confirms that the central supermassive black hole was once more than 100 million times brighter than its current state.

The BICEP Array will bring a new level of sensitivity to observations of cosmic microwave background polarization patterns on large angular scales, says Clem Pryke on behalf of the BICEP/Keck Collaboration.

The ‘new normal’ way of life for coping with the COVID-19 outbreak is a work in progress. When we move on, we should keep some of our adaptations rather than return to the old ways, for a more open and equitable way of working.

Solar imaging and spectral data indicate that impulsive heating through magnetic reconnection in transition region loops is responsible for observed transient brightenings, consistent with ion cyclotron turbulence due to strong currents at the reconnection sites.

The observed oriented directions of galaxy angular momentum vectors correlate with predicted directions based on the initial density field reconstructed from the positions of Sloan Digital Sky Survey galaxies, opening a way to probe fundamental physics in the early Universe.

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.

One of the giants of planetary science, H. J. Melosh, died unexpectedly on 11 September 2020 at age 73. Through his students, postdocs and collaborators, he brought a high level of physical rigour to the growing field of planetary geology.

The Milky Way disk is found to be moving with respect to the outer halo of the Galaxy as a result of the gravitational pull of the Large Magellanic Cloud as it falls into the Milky Way. Dynamical models of our Galaxy need to take this effect into account.

Two further radio bursts associated with magnetar SGR 1935+2154 have been detected with a Westerbork 25 m dish, bringing the total to four. These observations demonstrate that SGR 1935+2154, a putative Galactic analogue of a fast radio burst source, can emit bursts across seven orders of magnitude in energy.