Discs of gas and dust surrounding young stars are the birthplace of planets. However, the direct detection of protoplanets forming within discs has proved elusive to date. We present the detection of a large, localized deviation from Keplerian velocity in the protoplanetary disc surrounding the young star HD 163296. The observed velocity pattern is consistent with the dynamical effect of a two-Jupiter-mass planet orbiting at a radius ≈ 260 au from the star.

We present Phantom, a fast, parallel, modular and low-memory smoothed particle hydrodynamics and magnetohydrodynamics code developed over the last decade for astrophysical applications in three dimensions. The code has been developed with a focus on stellar, galactic, planetary and high energy astrophysics and has already been used widely for studies of accretion discs and turbulence, from the birth of planets to how black holes accrete. Here we describe and test the core algorithms as well as modules for magnetohydrodynamics, self-gravity, sink particles, dust-gas mixtures, H2 chemistry, physical viscosity, external forces including numerous galactic potentials, Lense-Thirring precession, Poynting-Robertson drag and stochastic turbulent driving. Phantom is hereby made publicly available.

We present 3D hydrodynamical models of the HD142527 protoplanetary disc, a bright and well studied disc that shows spirals and shadows in scattered light around a 100 au gas cavity, a large horseshoe dust structure in mm continuum emission, together with mysterious fast radial flows and streamers seen in gas kinematics. By considering several possible orbits consistent with the observed arc, we show that all of the main observational features can be explained by one mechanism -the interaction between the disc and the observed binary companion. We find that the spirals, shadows and horseshoe are only produced in the correct position angles by a companion on an inclined and eccentric orbit approaching periastron -the 'red' family from Lacour et al. (2016). Dust-gas simulations show radial and azimuthal concentration of dust around the cavity, consistent with the observed horseshoe. The success of this model in the HD142527 disc suggests other mm-bright transition discs showing cavities, spirals and dust asymmetries may also be explained by the interaction with central companions.

We still do not understand how planets form, or why extra-solar planetary systems are so different from our own solar system. But the last few years have dramatically changed our view of the discs of gas and dust around young stars. Observations with the Atacama Large Millimeter/submillimeter Array (ALMA) and extreme adaptive-optics systems have revealed 1 arXiv:1907.02538v1 [astro-ph.SR] 4 Jul 2019 that most -if not all -discs contain substructure, includind rings and gaps 1-3 , spirals 4-6 azimuthal dust concentrations 7 , and shadows cast by misaligned inner discs 5, 8 . These features have been interpreted as signatures of newborn protoplanets, but the exact origin is unknown. Here we report the kinematic detection of a few Jupiter-mass planet located in a gas and dust gap at 130 au in the disc surrounding the young star HD 97048. An embedded planet can explain both the disturbed Keplerian flow of the gas, detected in CO lines, and the gap detected in the dust disc at the same radius. While gaps appear to be a common feature in protoplanetary discs 2, 3 , we present a direct correspondence between a planet and a dust gap, indicating that at least some gaps are the result of planet-disc interactions.A variety of mechanisms have been proposed to explain the formation of rings and gaps in discs, e.g. snow-lines, non-ideal MHD effects, zonal flows, and self-induced dust-traps 9-13 . The most straightforward explanation is that the gaps are the results of forming planets interacting with the disc 14 . Recent ALMA surveys suggest that planets could indeed be responsible for carving out several of the observed gaps 2, 3, 15 , but until now definite evidence has remained elusive. Despite much effort, direct imaging of planets in young discs remains difficult. Many of the claimed detections have been refuted, or require confirmation [16][17][18] . The most promising detection to date is a companion imaged in the cleared inner disc around PDS 70 [19][20][21][22] . However, the mass estimate from photometry remains uncertain, and it is not yet clear if PDS 70 b falls within the planetary regime.Our approach is to search for the dynamical effect of a planet on the surrounding gas disc.

We present evidence for localised deviations from Keplerian rotation, i.e., velocity "kinks", in 8 of 18 circumstellar disks observed by the DSHARP program: DoAr 25, Elias 2-27, GW Lup, HD 143006, HD 163296, IM Lup, Sz 129 and WaOph 6. Most of the kinks are detected over a small range in both radial extent and velocity, suggesting a planetary origin, but for some of them foreground contamination prevents us from measuring their spatial and velocity extent. Because of the DSHARP limited spectral resolution and signal-to-noise in the 12 CO J=2-1 line, as well as cloud contamination, the kinks are usually detected in only one spectral channel, and will require confirmation. The strongest circumstantial evidence for protoplanets in the absence of higher spectral resolution data and additional tracers is that, upon deprojection, we find that all of the candidate planets lie within a gap and/or at the end of a spiral detected in dust continuum emission. This suggests that a significant fraction of the dust gaps and spirals observed by ALMA in disks are caused by embedded protoplanets.