Letters in 2017

The brightest galaxy in a cluster is known to align with its host filament in the local Universe. Here this correlation is extended to when the Universe was just a third of its current age. With this, the privileged history of brightest cluster galaxies is reinforced.

Using Si¹⁸O as a velocity tracer, evidence is reported for a rotating outflow driven by a magneto-centrifugal disk wind launched by a high-mass young stellar object. This rotation is a signature of the removal of angular momentum by an outflow.

Disk winds from the surfaces of protoplanetary disks remove angular momentum from radii outside ~10 au. Lee et al. show that residual angular momentum is removed at radii <10 au via highly collimated jets launched at the 0.05 au scale, enabling accretion.

Coevolving millions of cold dark matter particles and neutrinos within one N-body simulation, TianNu, shows that regions of similar dark matter density can have different neutrino densities. These density variations may have an effect on the cosmic structure.

Gender discrimination is very much an issue in academia generally and in astronomy specifically. Through machine learning techniques, astronomy papers authored by women are shown to have 10% systematically fewer citations than those authored by men.

Oxygen isotope measurements from unequilibrated enstatite chondrites produce a steep slope on a three-isotope plot. This can be explained by the occurrence of silicate–SiO reactions in the early stages of the Solar System’s protoplanetary disk.

Orbital parameters for the seventh Earth-sized transiting planet around star TRAPPIST-1 are reported, along with an investigation into the complex three-body resonances linking every member of this planetary system.

A magnetohydrodynamic model is able to explain the peak brightness point offset variations in the atmosphere of the hot giant exoplanet HAT-P-7 b with wind variability. A minimum field strength of 6 G is required to reproduce the observations.

ALMA observations of TW Hydrae in the 13C18O J = 3–2 molecular line probe the mid-plane of the circumstellar disk where giant planets are expected to form. With other lines, the gas mass distribution, temperature and the gas-to-dust ratio are determined.

Cassini’s camera observed Titan from orbit at different angles (0–166°) and found that the planet looks brighter towards the night than at midday. This effect, linked to the scattering properties of Titanian haze, can also be present in exoplanets.

The detection of a metal-polluted G star in a binary system with an invisible X-ray source offset from the centre of a supernova remnant leads to the suggestion that this was the progenitor pair behind a core-collapse supernova in RCW 86.

The authors put together measurements of ions and neutral atoms from Cassini and the two Voyagers and find that the heliosphere responds quickly (with a lag of 2–3 years) to the solar cycle and that it is bubble-shaped and not tail-shaped, as usually schematized.

A faint galaxy has been detected in the very early Universe thanks to deep observations and a massive cluster gravitationally magnifying its emission. One out of only five such galaxies known, this detection constrains how the Universe was reionized.

The discovery of several Kuiper belt objects (KBOs) with anomalous properties (they are blue-coloured, whereas KBOs of the same type are red, and they are all binaries) gives constraints on formation processes in the outermost region of the Solar System.

Global-scale Rossby waves develop in planets’ atmospheres and influence their weather. Now, similar waves, driven by magnetism, are unambiguously detected on the Sun. They can possibly help the forecasting of solar activity and related space weather.

Magnetic energy powers explosive flares on the Sun. Now, observations of unprecedented resolution identify the precursors of such flares in the lower solar atmosphere. These findings will help to constrain theoretical models of flare formation.

A bright outburst of activity from the nucleus of comet 67P, observed by Rosetta in July 2015, is traced back to a cliff that partially collapsed at the same time as the outburst, establishing a link between the two events. The collapse has also exposed the fresh ice present under the surface.

The abundance of Be and V isotopes in calcium–aluminium-rich inclusions (CAIs), the oldest solids in the Solar System, shows that CAIs were irradiated by a gradual flux of radiation from solar flares when the Sun was young and more energetic, for a short time (300 yr) and at close distance (≈0.1 au).

Cassini’s RADAR has surveyed a region close to Enceladus’s ‘tiger stripes’. It finds a temperate subsurface with warm cracks, indicating that the moon’s icy crust is only a few kilometres thick at these points. A dormant crack hints at episodic geological activity.

Using asteroseismology to measure the spin axes of stars in two old open star clusters, Corsaro et al. find alignment between significant numbers of stars. It is thought that this is an imprint of the original angular momentum of the parent molecular cloud.