The current standard model of cosmology successfully describes a variety of measurements, but the nature of its main ingredients, dark matter and dark energy, remains unknown. Euclid is a medium-class mission in the Cosmic Vision 2015–2025 programme of the European Space Agency (ESA) that will provide high-resolution optical imaging, as well as near-infrared imaging and spectroscopy, over about 14 000 deg² of extragalactic sky. In addition to accurate weak lensing and clustering measurements that probe structure formation over half of the age of the Universe, its primary probes for cosmology, these exquisite data will enable a wide range of science. This paper provides a high-level overview of the mission, summarising the survey characteristics, the various data-processing steps, and data products. We also highlight the main science objectives and expected performance.

Aims. Our scientific goal is to provide revised membership lists of the α Per, Pleiades, and Praesepe clusters exploiting the second data release of Gaia and produce five-dimensional maps (α, δ, π, μ_α cos δ, μ_δ) of these clusters. Methods. We implemented the kinematic method combined with the statistical treatment of parallaxes and proper motions to identify astrometric member candidates of three of the most nearby and best studied open clusters in the sky. Results. We cross-correlated the Gaia catalogue with large-scale public surveys to complement the astrometry of Gaia with multi-band photometry from the optical to the mid-infrared. We identified 517, 1248, and 721 bona fide astrometric member candidates inside the tidal radius of α Per, the Pleiades, and Praesepe, respectively. We cross-matched our final samples with catalogues from previous surveys to address the level of completeness. We update the main physical properties of the clusters, including mean distance and velocity, as well as core, half-mass, and tidal radii. We infer updated ages from the white dwarf members of the Pleiades and Praesepe. We derive the luminosity and mass functions of the three clusters and compare them to the field mass function. We compute the positions in space of all member candidates in the three regions to investigate their distribution in space. Conclusions. We provide updated distances and kinematics for the three clusters. We identify a list of members in the α Per, Pleiades, and Praesepe clusters from the most massive stars all the way down to the hydrogen-burning limit with a higher confidence and better astrometry than previous studies. We produce complete 5D maps of stellar and substellar bona fide members in these three regions. The photometric sequences derived in several colour–magnitude diagrams represent benchmark cluster sequences at ages from 90 to 600 Myr. We note the presence of a stream around the Pleiades cluster extending up to 40 pc from the cluster centre.

We present the discovery of a companion near the deuterium burning mass limit located at a very wide distance, at an angular separation of 4.6+/-0.1 arcsec (projected distance of ~ 670 AU) from UScoCTIO108, a brown dwarf of the very young Upper Scorpius association. Optical and near-infrared photometry and spectroscopy confirm the cool nature of both objects, with spectral types of M7 and M9.5, respectively, and that they are bona fide members of the association, showing low gravity and features of youth. Their masses, estimated from the comparison of their bolometric luminosities and theoretical models for the age range of the association, are 60+/-20 and 14^{+2}_{-8} MJup, respectively. The existence of this object around a brown dwarf at this wide orbit suggests that the companion is unlikely to have formed in a disk based on current planet formation models. Because this system is rather weakly bound, they did not probably form through dynamical ejection of stellar embryos.Comment: 10 pages, including 4 figures and 2 table

We have prepared solutions of multiwalled carbon nanotubes in Aroclor 1254, a mixture of polychlorinated biphenyls. The solutions are stable at room temperature. Transport measurements were performed using a scanning-tunneling probe on a sample prepared by spin coating the solution on gold substrates. Conductance steps were clearly seen. A histogram of a high number of traces shows maximum peaks at integer values of the conductance quantum $G_0=2e^2/h$, demonstrating ballistic transport at room temperature along the carbon nanotube over distances longer than $1.4\mu \mathrm{m}$.

Aims. Our scientific goal is to provide a 3D map of the nearest open cluster to the Sun, the Hyades, combining the recent release ofGaiaastrometric data, ground-based parallaxes of sub-stellar member candidates and photometric data from surveys which cover large areas of the cluster.Methods. We combined the secondGaiarelease with ground-basedH-band parallaxes obtained with the infrared camera on the 2 m robotic Liverpool telescope to astrometrically identify stellar and sub-stellar members of the Hyades, the nearest open cluster to the Sun.Results. We find 1764 objects within 70° radius from the cluster centre from theGaiasecond data release, whose kinematic properties are consistent with the Hyades. We limit our study to 30 pc from the cluster centre (47.03 ± 0.20 pc) where we identify 710 candidate members, including 85 and 385 in the core and tidal radius, respectively. We determine proper motions and parallaxes of eight candidate brown dwarf members and confirm their membership. Using the 3D positions and a model-based mass-luminosity relation we derive a luminosity and mass function in the 0.04–2.5M_⊙range. We confirm evidence for mass segregation in the Hyades and find a dearth of brown dwarfs in the core of the cluster. From the white dwarf members we estimate an age of 640₋₄₉⁺⁶⁷Myr.Conclusions. We identify a list of members in the Hyades cluster from the most massive stars down to the brown dwarfs. We produce for the first time a 3D map of the Hyades cluster in the stellar and sub-stellar regimes and make available the list of candidate members.