Research articles

Cromartie et al. have probably found the most massive neutron star discovered so far by combining NANOGrav 12.5-yr data with radio data from the Green Bank Telescope. Millisecond pulsar J0740+6620 has a mass of 2.14 M_⊙, ~0.1 M_⊙ more massive than the previous record holder, and very close to the upper limit on neutron star masses from Laser Interferometer Gravitational-Wave Observatory measurements.

K2-18 b is a planet with a mass around eight times that of the Earth that lies within the standard habitable zone of its star. Hubble spectra show the presence of an atmosphere around K2-18 b containing significant amounts of water vapour (up to a few tens of per cent, depending on the spectral model), but also a non-negligible amount of H₂–He.

The range of sizes of old star clusters in the LMC does not necessarily imply the presence of binary black holes within them; the spread can be explained as a consequence of internal dynamical evolution and formation conditions. Looking at five old LMC clusters, Ferraro et al. find signs of dynamical youth.

An extensive survey to search for members of the only known Kuiper belt family, named after the parent body Haumea, found no family members fainter than absolute magnitude H_r = 7.9, significantly brighter than the detection limit (H_r = 9.5). This lack of small members is inconsistent with a catastrophic disruption as the origin of the Haumea family.

The X-ray pulsar wind nebula around PSR B0540–69 brightened by about a third after a change in the pulsar’s spin-down rate. This phenomenon, which has not previously been seen in this way in other pulsars, is likely to be due to a sudden change in the pulsar’s magnetosphere.

Phase curves from a sample of 12 hot Jupiters show that this type of planet keeps the same nightside temperature (~1,100 K) regardless of the irradiation they receive from their star. This effect is due to an optically thick layer of the same species of clouds on the nightside hemisphere.

Radial velocity data of the young β Pictoris system acquired by HARPS and spanning 15 years show evidence of β Pic c, a gas giant of ~9 Jupiter masses orbiting on an eccentric orbit at ~2.4 au from the star, near the theoretical snowline. Both β Pic b and c, located close to the star, may have formed in situ by core accretion.

A glitch experienced by the Vela pulsar in 2016 has been studied in detail, revealing a curious slowdown of the neutron star’s rotation immediately before the event, and confirming some theoretical predictions of neutron-star physics.

Pinte et al. report the kinematic detection of a few-Jupiter-mass planet orbiting at 130 au from the young star HD 97048. The radial position of the planet coincides with a gap in both the gas and dust components of the protoplanetary disk, showing that at least some gaps can be linked to the presence of planets.

Graphene doped to the Dirac point can be used to detect signals from 90 to 700 GHz, and prospectively across the entire terahertz range, with high sensitivity. Such a sensor could be used in next-generation space-based telescopes, promising quantum-limited detection that surpasses superconducting technologies.

By using a superconducting integrated circuit to filter incoming millimetre, submillimetre and far-infrared light from distant galaxies, a prototype spectrometer holds promise for wideband spectrometers that are small, sensitive and scalable to wideband spectroscopic imagers.

The Transiting Exoplanet Survey Satellite (TESS) has identified a nearby, bright, quiescent M dwarf star that hosts two sub-Neptune-sized planets and one super-Earth-sized planet. The system is eminently suitable for follow-up studies of transit timing variations, radial velocity measurements and transmission spectroscopy.

The measured magnetic field strengths of four close-in gas giant planets are reported, using a technique based on magnetic star–planet interactions. Values range from 20 G to 120 G, close to estimates based on planetary internal heat flux, but ~10–100 times larger than predicted by dynamo scaling laws.

Stars in the Milky Way halo are older than those in its thick disk, with their ten-billion-year age distribution cutoff marking the accretion of Gaia-Enceladus to the Milky Way. The red-sequence halo stars are those formed first in the Milky Way progenitor, constituting its long-sought in situ halo.

Of the 72 known fast radio burst (FRB) sources only two have been observed to emit repeat bursts. By calculating the volumetric occurrence rate of non-repeating FRBs, Vikram Ravi shows that there are not enough candidate cataclysmic progenitor events for most FRBs to be one-off phenomena, and therefore most FRBs must repeat.

A combination of laboratory experiments and numerical modelling shows that a 2–3 cm-thick layer of silica aerogel deployed over the temperate regions of Mars could maintain a surface environment conducive to liquid water all year round. Such an approach would create a habitable setting for photosynthetic life.

The MASCOT lander observed a boulder on the surface of asteroid Ryugu up close. The boulder’s low thermal inertia is closer to fine regolith or comets rather than stony boulders, indicating high porosity and low tensile strength. Orbit measurements confirm that Ryugu’s surface is covered with similar boulders.

The Juno spacecraft’s observations of magnetic field perturbations in Jupiter’s polar regions show Birkeland currents associated with aurorae that are weaker than anticipated and filamentary in nature. An asymmetry is observed between the northern and southern auroras.

Full cosmological hydrodynamical simulations employing modified gravity find that disk galaxies can form and their stellar properties are only mildly affected. Modified gravity leaves signatures on large-scale structure observable with the Square Kilometre Array.

Tamanini and Danielski show that LISA will be sensitive enough to detect (massive) exoplanets orbiting double white-dwarf systems using gravitational waves. This population of exoplanets cannot be probed by other means, and detections will reveal potentially significant numbers of planets in the Galaxy and Magellanic Clouds.