Articles in 2021

The planetary architecture of the Solar System and its isotopic dichotomy can be reproduced using a protoplanetary disk model structured with rings and gaps, as commonly seen in protoplanetary disks around other stars.

Observations of some so-called ‘water fountain’ stars show that they appear to have lost a large fraction of their initial mass in a very short time (hundreds of years). This leads Khouri et al. to suggest that these sources have undergone the poorly understood process of common-envelope evolution, where the envelope of one star engulfs that of its companion.

Magnetospheres of exoplanets are vast, tenuous and hard to detect. Deep blue-shifted absorption lines observed in the extended region around HAT-P-11 b may provide evidence for a magnetosphere and magnetotail.

This Article reports the detection of oscillations in the massive star β Crucis using polarized light. Such oscillatory modes provide information about stellar structure; in this case the stellar mass, inclination of the rotation axis and size of the convective core.

Water and hydroxyl enrichment in the solar-wind-irradiated rim of an olivine grain from asteroid Itokawa suggests that its regolith could contain ~20 l m⁻³ of water from solar wind—a potential water source for airless planetary bodies.

Up to 40% of ultra-diffuse galaxies could have formed via stripping of material by ram pressure. A study on 11 low-mass post-starburst galaxies in the Coma and Abell 2147 clusters shows ubiquitous marks of ram-pressure stripping and recent star formation, and most of them will evolve into ultra-diffuse galaxies in the next 10 Gyr.

Wet chemistry experiments performed in situ by the Curiosity rover in the sand of Bagnold Dunes detected an array of organic molecules including aromatic benzoic acid, nitrogen-bearing organics and other unidentified compounds.

A sensitive Breakthrough Listen search for technosignatures towards Proxima Centauri has resulted in a viable narrowband signal. The observational approach, using the Parkes Murriyang telescope, is described here, while the signal of interest is analysed in a companion paper by Sheikh et al.

A radio signal detected in the direction of Proxima Centauri in a Breakthrough Listen programme is analysed for signs that it was transmitted by extraterrestrial intelligent life, using a newly developed framework. However, the signal ‘blc1’ is likely to be terrestrial radio-frequency interference.

A brightness dip in the extragalactic X-ray binary M51-ULS-1 can be well fit by a planet transit model in which the eclipser is most likely Saturn-sized. The locations of possible orbits are consistent with the survival of a planet bound to a mass-transfer binary.

The impact flux in the inner Solar System just after its formation is studied by looking at the highly siderophile element abundance of Vesta. Results show that leftover planetesimals from the terrestrial planet region have been the major impactor source, indicative of a skewed mass distribution in the primordial inner Solar System.

Rather than cooling down according to a well-established rate, some ~70% of the white dwarfs in globular cluster M13 are delaying their stellar demise by burning left-over hydrogen conserved by skipping the third dredge-up event.

Chemical inhomogeneities between the two members of a binary star system, where the stars presumably are formed from the same material, could be due to planetary engulfment. Such a fate has befallen planets around a quarter of Sun-like (in temperature and surface gravity) stars, according to this sample of more than 100 binary systems.

Annular (zonally symmetric) atmospheric modes, common on Earth, are found on both Mars and Titan via observations and general circulation models. On Mars, they have considerable impact on dust activity and could be used to predict dust storms. On Titan, they could be linked to sporadic cloud outbursts.

Multi-spacecraft observations of temperature, dust and water ice opacities, water vapour abundances, and thermospheric hydrogen in the atmosphere of Mars during a local dust storm show that even such regional events, much more frequent than global dust storms, can boost global atmospheric escape by a factor of five to ten.

A long-duration campaign to image the Sun’s middle corona—a region about 1.5–3 solar radii from the centre—reveals three dynamical processes that shape and restructure the middle corona. The dynamics can influence the global coronal structure and beyond.

Far-UV observations from the Hubble Space Telescope provide evidence of water vapour in the tenuous atmosphere of Ganymede. Atmospheric water originates from surface ice sublimation, with an enrichment in the subsolar region and substantial asymmetry between the leading and trailing hemispheres.

Modelling shows that impact gardening on Europa has the potential to churn the shallow subsurface material down to 30 cm very efficiently and globally, thus destroying potential habitable niches just below the surface. Some areas where both gardening and radiation are relatively weak are, however, identified.

Fully three-dimensional magnetohydrodynamic simulations show that solar eruptions can be simply and efficiently initiated in a single bipolar configuration through photospheric shearing motion alone, without the need of any additional special topology.

Photochemical hazes in exoplanet atmospheres work as opacity barriers, hindering characterization of the atmospheres themselves. Here laboratory experiments quantify the haze surface energies that factor into the removal of hazes from atmospheres, which, when added to existing data on haze production, give a greater understanding of haze properties.