Research articles

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  • A 4.8σ exomoon candidate is found around gas giant Kepler-1708 b, which orbits at 1.6 au around its star. It is the only candidate from a dedicated survey that analysed 70 cool giant exoplanets discovered by Kepler. Kepler-1708 b-i has a radius of 2.6 Earth radii and orbits its planet at 12 planetary radii.

    • David Kipping
    • Steve Bryson
    • Alex Teachey
    Article Open Access
  • The episodic but protracted delivery of foundering cold material (diapirs) to the lunar core during the first billion years activated vigorous core convection that generated peaks of high intensity in the magnetic field. This process can explain the magnetic record of lunar rocks.

    • Alexander J. Evans
    • Sonia M. Tikoo
    Letter
  • The 2,000-au-long streamer of material from binary protostar Z CMa can be explained by the flyby of an object some 4,700 au away, now revealed through high-spatial-resolution ALMA and JVLA observations.

    • Ruobing Dong
    • Hauyu Baobab Liu
    • Motohide Tamura
    Letter
  • High-spectral-resolution data from the CARMENES spectrometer could resolve the neutral oxygen triple line at 777.4 nm in the atmosphere of ultrahot Jupiter KELT-9b. The results show the presence of non-local thermodynamic equilibrium processes and reveal macro- and microturbulence induced by fast winds with speeds ranging between 3 and 13 km s−1.

    • Francesco Borsa
    • Luca Fossati
    • Denis Shulyak
    Letter
  • An evolutionary model of the solar protoplanetary disk that includes the decrease of its viscosity with time and the accretion of gas from the interstellar medium shows that planetesimals formed simultaneously in two locations: at the water snowline (~5 au) and at the silicate sublimation line (~1 au), explaining the observed isotopic dichotomy of iron meteorites.

    • A. Morbidelli
    • K. Baillié
    • T. Kleine
    Letter
  • The MicrOmega imaging spectrometer performed a first characterization of the sample returned from asteroid Ryugu by Hayabusa2. Compositional homogeneity dominates down to millimetre scales, with signatures of hydrated phases and organics. At the submillimetre scale, NH-rich compounds and alteration products such as carbonates are detected.

    • C. Pilorget
    • T. Okada
    • J.-P. Bibring
    Letter
  • The Hayabusa2 spacecraft returned 5.4 g of material from the asteroid Ryugu. A first analysis of the samples found an estimated density of 1,282 ± 231 kg m−3, considerably lower than even the most porous meteorites. Together with preliminary spectral analysis, these results indicate that Ryugu is similar to CI chondrites, but darker, more porous and more brittle.

    • Toru Yada
    • Masanao Abe
    • Yuichi Tsuda
    Letter Open Access
  • 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.

    • Theo Khouri
    • Wouter H. T. Vlemmings
    • Raghvendra Sahai
    Article
  • An energetic eruptive filament on EK Draconis most probably launched a coronal mass ejection with a mass ten times larger than the largest solar coronal mass ejection. Studying such ejections provides insight into stellar angular momentum loss and the habitability of orbiting planets.

    • Kosuke Namekata
    • Hiroyuki Maehara
    • Kazunari Shibata
    Letter Open Access
  • The Zhurong rover has explored its landing site in Utopia Planitia, Mars, and is travelling south towards the highland–lowland boundary, focusing initially on the composition and physical properties of the rocks along the way.

    • Jianjun Liu
    • Chunlai Li
    • Hongbo Zhang
    Letter Open Access