Newly forming proto-planets are expected to create cavities and substructures in young, gas-rich proto-planetary disks [1-3], but they are difficult to detect as they could be confused with disk features affected by advanced image-analysis techniques[4,5]. Recently, a planet was discovered inside the gap of the transitional disk of the T-Tauri star PDS 70[6,7]. Here we report on the detection of strong H-alpha emission from two distinct locations in the PDS 70 system, one corresponding to the previously discovered planet PDS 70 b, which confirms the earlier Hα detection[8], and another located close to the outer-edge of the gap, coinciding with a previously identified bright dust spot in the disk and with a small opening in a ring of molecular emission[6,7,9]. We identify this second Hα peak as a second proto-planet in the PDS 70 system. The Hα emission spectra of both proto-planets indicate ongoing accretion onto the proto-planets[10,11], which appear to be near a 2:1 mean motion resonance. Our observations show that adaptive-optics-assisted, medium-resolution, integral-field spectroscopy with MUSE[12] targeting accretion signatures will be a powerful way to trace ongoing planet formation in transitional disks at different stages of their evolution. Finding more young planetary systems in mean motion resonance would give credibility to the Grand Tack hypothesis in which Jupiter and Saturn migrated in a resonance orbit during the early formation period of our Solar System[13].PDS 70 (V* V1032 Cen) is a young T-tauri star at a distance of 113. 43+-0.52 pc [14,15] with a spectroscopically determined age of 5. . Its proto-planetary disk was first discovered through spectral energy distribution(SED) modelling [16], and later directly imaged at near-infrared and sub-mm wavelengths [9,17,18]. Both the SED modelling and direct imaging show that PDS 70 harbours a transitional disk in which a large radial region from 20 AU -40 AU [6,18], as seen in the near-infrared, is

Context. Ground-based high-dispersion (R ∼ 100 000) spectroscopy (HDS) is proving to be a powerful technique with which to characterize extrasolar planets. The planet signal is distilled from the bright starlight, combining ral and time-differential filtering techniques. In parallel, high-contrast imaging (HCI) is developing rapidly, aimed at spatially separating the planet from the star. While HDS is limited by the overwhelming noise from the host star, HCI is limited by residual quasi-static speckles. Both techniques currently reach planet-star contrast limits down to ∼10 −5 , albeit for very different types of planetary systems. Aims. In this work, we discuss a way to combine HDS and HCI (HDS+HCI). For a planet located at a resolvable angular distance from its host star, the starlight can be reduced up to several orders of magnitude using adaptive optics and/or coronography. In addition, the remaining starlight can be filtered out using high-dispersion spectroscopy, utilizing the significantly different (or Doppler shifted) high-dispersion spectra of the planet and star. In this way, HDS+HCI can in principle reach contrast limits of ∼10 −5 ×10 −5 , although in practice this will be limited by photon noise and/or sky-background. In contrast to current direct imaging techniques, such as Angular Differential Imaging and Spectral Differential Imaging, it will work well at small working angles and is much less sensitive to speckle noise. For the discovery of previously unknown planets HDS+HCI requires a high-contrast adaptive optics system combined with a high-dispersion R ∼ 100 000 integral field spectrograph (IFS). This combination currently does not exist, but is planned for the European Extremely Large Telescope. Methods. We present simulations of HDS+HCI observations with the E-ELT, both probing thermal emission from a planet at infrared wavelengths, and starlight reflected off a planet atmosphere at optical wavelengths. For the infrared simulations we use the baseline parameters of the E-ELT and METIS instrument, with the latter combining extreme adaptive optics with an R = 100 000 IFS. We include realistic models of the adaptive optics performance and atmospheric transmission and emission. For the optical simulation we also assume R = 100 000 IFS with adaptive optics capabilities at the E-ELT. Results. One night of HDS+HCI observations with the E-ELT at 4.8 μm (Δλ = 0.07 μm) can detect a planet orbiting α Cen A with a radius of R = 1.5 R earth and a twin-Earth thermal spectrum of T eq = 300 K at a signal-to-noise (S/N) of 5. In the optical, with a Strehl ratio performance of 0.3, reflected light from an Earth-size planet in the habitable zone of Proxima Centauri can be detected at a S/N of 10 in the same time frame. Recently, first HDS+HCI observations have shown the potential of this technique by determining the spin-rotation of the young massive exoplanet β Pictoris b. Conclusions. The exploration of the planetary systems of our neighbor stars is of great scientific and philosophical value. The HD...

Solar faculae appear as bright small features close to the solar limb. Recent high-resolution images show these brightenings in unprecedented detail. Our analysis of numerical MHD simulations reproduces the observed smallscale features. The simulations reveal that faculae originate from a thin layer within granules just below largely transparent magnetic flux concentrations. This is basically the "bright wall" model of Spruit. The dark, narrow lanes often associated with faculae occur at the opposite side of the magnetic flux concentration and are due to an extended layer with lower-than-average temperature.

A solar photospheric "thermal profiling" analysis is presented, exploiting the infrared (2.3-4.6 µm) rovibrational bands of carbon monoxide (CO) as observed with the McMath-Pierce Fourier transform spectrometer (FTS) at Kitt Peak, and from above the Earth's atmosphere by the Shuttle-borne ATMOS experiment. Visible continuum intensities and center-limb behavior constrained the temperature profile of the deep photosphere, while CO center-limb behavior defined the thermal structure at higher altitudes. The oxygen abundance was self consistently determined from weak CO absorptions (for C/O≡ 0.5). Our analysis was meant to complement recent studies based on 3-D convection models which, among other things, have revised the historical solar oxygen (and carbon) abundance downward by a factor of nearly two; although in fact our conclusions do not support such a revision. Based on various considerations, an ǫ O = 700±100 ppm (parts per million relative to hydrogen) is recommended; the large uncertainty reflects the model sensitivity of CO. New solar isotopic ratios also are reported: 12 C/ 13 C=80±1, 16 O/ 17 O=1700±220, and 16 O/ 18 O=440±6; all significantly lower than terrestrial. CO synthesis experiments utilizing a stripped down version of the 3-D model-which has large temperature fluctuations in the middle photosphere, possibly inconsistent with CO "movies" from the Infrared

Abstract.To clarify the physical nature of the enigmatic scattering polarization in the Na i D1 and D2 line cores we have explored their behavior with full Stokes vector polarimetry in regions with varying degree of magnetic activity near the solar limb. These observations represent the first time that ZIMPOL II, the second generation of our CCD based imaging polarimeter systems, has been used for a scientific program. With ZIMPOL II the four Stokes images can be demodulated and recorded with a single CCD sensor such that the resulting images of the fractional polarization Q/I, U/I, and V /I are entirely free from spurious features due to seeing or flat-field effects. The polarization in the cores of the lines, in particular in D2, exhibits dramatic and unexpected spatial variations in both Q/I and U/I, including polarization self-reversals of the D2 Q/I core peak. As the fluctuations in the Q, U , and V parameters appear to be relatively uncorrelated, we have parametrized the profiles and made scatter plots of the extracted parameters. Comparison with synthetic scatter plots based on different theoretical models suggests that the polarization signals in the cores of the D2 and D1 lines have different physical origins: While the D1 core is likely to be governed by ground-state atomic polarization, the D2 core is dominated by the alignment of the excited state and by effects of partial frequency redistribution.

Aims. We studied the well-known circumstellar disk around the Herbig Ae/Be star HD 97048 with high angular resolution to reveal undetected structures in the disk which may be indicative of disk evolutionary processes such as planet formation. Methods. We used the IRDIS near-IR subsystem of the extreme adaptive optics imager SPHERE at the ESO/VLT to study the scattered light from the circumstellar disk via high resolution polarimetry and angular differential imaging. Results. We imaged the disk in unprecedented detail and revealed four ring-like brightness enhancements and corresponding gaps in the scattered light from the disk surface with radii between 39 au and 341 au. We derived the inclination and position angle as well as the height of the scattering surface of the disk from our observational data. We found that the surface height profile can be described by a single power law up to a separation ∼270 au. Using the surface height profile we measured the scattering phase function of the disk and found that it is consistent with theoretical models of compact dust aggregates. We discuss the origin of the detected features and find that low mass (≤1 M Jup ) nascent planets are a possible explanation.

Context. The Kepler object KIC 12557548 b is peculiar. It exhibits transit-like features every 15.7 h that vary in depth between 0.2% and 1.2%. Rappaport et al. (2012, ApJ, 752, 1) explain the observations in terms of a disintegrating, rocky planet that has a trailing cloud of dust created and constantly replenished by thermal surface erosion. The variability of the transit depth is then a consequence of changes in the cloud optical depth. Aims. We aim to validate the disintegrating-planet scenario by modeling the detailed shape of the observed light curve, and thereby constrain the cloud particle properties to better understand the nature of this intriguing object. Methods. We analyzed the six publicly-available quarters of raw Kepler data, phase-folded the light curve and fitted it to a model for the trailing dust cloud. Constraints on the particle properties were investigated with a light-scattering code.Results. The light curve exhibits clear signatures of light scattering and absorption by dust, including a brightening in flux just before ingress correlated with the transit depth and explained by forward scattering, and an asymmetry in the transit light curve shape, which is easily reproduced by an exponentially decaying distribution of optically thin dust, with a typical grain size of 0.1 μm. Conclusions. Our quantitative analysis supports the hypothesis that the transit signal of KIC 12557548 b is due to a variable cloud of dust, most likely originating from a disintegrating object.

To assess the impact of atmospheric aerosols on health, climate, and air traffic, aerosol properties must be measured with fine spatial and temporal sampling. This can be achieved by actively involving citizens and the technology they own to form an atmospheric measurement network. We establish this new measurement strategy by developing and deploying iSPEX, a low-cost, mass-producible optical add-on for smartphones with a corresponding app. The aerosol optical thickness (AOT) maps derived from iSPEX spectropolarimetric measurements of the daytime cloud-free sky by thousands of citizen scientists throughout the Netherlands are in good agreement with the spatial AOT structure derived from satellite imagery and temporal AOT variations derived from ground-based precision photometry. These maps show structures at scales of kilometers that are typical for urban air pollution, indicating the potential of iSPEX to provide information about aerosol properties at locations and at times that are not covered by current monitoring efforts.