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High-resolution gravity data from Dawn’s second extended mission could probe the global and local structure of Ceres’s crust. The results show significant spatial and vertical variations of crustal density and porosity, associated with ice features and ice-related processes driven from the interior, and impacts.
High-resolution data of Ceres’s bright spots (faculae), obtained by Dawn’s second extended mission, suggest the existence of a deep brine-rich reservoir that emerged to the surface through long-lived cryovolcanic activity as a consequence of the impact that created Occator crater.
Global images of helium and hydrogen emission are used to directly derive the helium abundance out to 2.2R⊙. The helium abundance is shaped by the large-scale coronal magnetic field. Helium is almost completely depleted near the equator in the quiet Sun.
A large streamer of infalling material joins the dense core with the accretion disk around a young protostar, where the streamer is linked to disk structures. This finding demonstrates the importance of a big-picture viewpoint when studying small-scale accretion features.
Observations of the X8.2 solar flare, which happened on 2017 September 10, could spatially resolve the distribution of the energetic electrons along the reconnection current sheet. More than 99% of them are concentrated at the bottom of the current sheet, not at the reconnection X point.
Stellar intensity interferometry (SII) is undergoing a revival. Here, data from the four 12 m optical reflectors of the VERITAS array are correlated post facto to determine the angular diameter of two stars to a high precision, laying the groundwork for SII at future large Cherenkov arrays.
Conditions in an accretion burst around a high-mass young stellar object (HMYSO) were sufficient to pump two species previously not known to maser. HDO and HNCO were found to trace spiral-arm features in the accretion flow onto the HMYSO.
Low-mass stars are expected to destroy their lithium content as they evolve, but this study of stars in the red clump evolutionary stage shows that their lithium abundance is on average forty times greater than at the end of the previous stage, something not predicted by theory.
Statistical analysis of velocity fluctuations in the interstellar medium (ISM) of the Milky Way and NGC 4321 show that the motion of molecular gas over scales ranging from 0.1 to 1,000 pc is similar, and consistent with that generated by a combination of gravity and turbulence. ISM structure at one scale is therefore linked to structure at other scales.
The oxygen emission at 557.7 nm, responsible for the green colour of auroras on Earth, is present in two layers at 80 and 120 km altitude on the dayside atmosphere of Mars. Simultaneous observations of the oxygen both in this visible line and in the ultraviolet could also constrain the elusive visible/ultraviolet intensity ratio of the auroral emission to a value of 16.5.
Titan is migrating away from Saturn on a much shorter timescale than expected, lending support to the resonance-locking tidal theory. This result motivates a revision of the evolutionary history of Saturn’s moon system and may be relevant to other giant planets.
A detailed microphysical model shows that there are two distinct regimes in the aerosol composition of exoplanetary atmospheres: silicates dominate at atmospheric temperatures above 950 K, whereas hydrocarbons prevail for temperatures below 950 K.
A ring galaxy is found at a look-back time of 10.8 Gyr. The diffuse stellar light outside the star-forming ring, the ring’s radial velocity and a nearby intruder galaxy indicate that this is a collisional ring galaxy.
A map of the stability of brines on Mars, obtained by combining thermodynamic and climate modelling, shows that some brines can stay liquid for longer than previously thought, particularly at high northern latitudes. However, they are not habitable to known terrestrial life, and can be explored without risk of biological contamination from Earth.
A soft X-ray polarimetry capability has been missing from astronomy since the late 1970s. Here a CubeSat polarimeter named PolarLight has detected the Crab nebula and pulsar in the soft X-ray band, measuring their polarized emission. PolarLight observed a pulsar glitch, with an associated polarization change.
High-resolution radiation-hydrodynamic simulations of galaxy clusters show that extended cold gas filaments can form in the centre of clusters through the combination of radiative cooling and ram pressure from feedback driven by the central active galactic nucleus.
A MESSENGER flyby of Venus has detected a difference in N2 composition between the upper and lower atmosphere. The presence of substantially distinct regions within Venus’s atmosphere has implications on remote sensing techniques for exoplanets.
Hubble Space Telescope data show that interstellar comet 2I/Borisov has an unusually high CO/H2O ratio—higher than any other comet that has been seen in the inner regions of our Solar System. This allows us to constrain the nature and location of the circumstellar region from which 2I/Borisov originated.
Interstellar comet Borisov has thus far looked very much like a Solar System comet in terms of its volatile content, but with new data from ALMA that show robust detections of CO and HCN, it is clear that Borisov is rich in CO, helping to pinpoint its origin.
Tidal fragmentation of a planetary body that orbited too close to its star can explain all the peculiar characteristics of the interstellar visitor ‘Oumuamua, a formation model shows. Kilometre-sized comets, super-Earths and sub-Neptune exoplanets around subsolar stars or white dwarfs are the most probable parent bodies.
