, U. hopp 5,6 , C. Haumea-one of the four known trans-Neptunian dwarf planetsis a very elongated and rapidly rotating body 1-3 . In contrast to other dwarf planets [4][5][6] , its size, shape, albedo and density are not well constrained. The Centaur Chariklo was the first body other than a giant planet known to have a ring system 7 , and the Centaur Chiron was later found to possess something similar to Chariklo's rings 8,9 . Here we report observations from multiple Earth-based observatories of Haumea passing in front of a distant star (a multichord stellar occultation). Secondary events observed around the main body of Haumea are consistent with the presence of a ring with an opacity of 0.5, width of 70 kilometres and radius of about 2,287 kilometres. The ring is coplanar with both Haumea's equator and the orbit of its satellite Hi'iaka. The radius of the ring places it close to the 3:1 mean-motion resonance with Haumea's spin period-that is, Haumea rotates three times on its axis in the time that a ring particle completes one revolution. The occultation by the main body provides an instantaneous elliptical projected shape with axes of about 1,704 kilometres and 1,138 kilometres. Combined with rotational light curves, the occultation constrains the three-dimensional orientation of Haumea and its triaxial shape, which is inconsistent with a homogeneous body in hydrostatic equilibrium. Haumea's largest axis is at least 2,322 kilometres, larger than previously thought, implying an upper limit for its density of 1,885 kilograms per cubic metre and a geometric albedo of 0.51, both smaller than previous estimates 1, 10,11 . In addition, this estimate of the density of Haumea is closer to that of Pluto than are previous estimates, in line with expectations. No global nitrogen-or methane-dominated atmosphere was detected.Within our programme of physical characterization of trans-Neptunian objects (TNOs), we predicted an occultation of the star URAT1 533− 182543 by the dwarf planet (136108) Haumea and arranged observations as explained in Methods. Positive occultation detections were obtained on 2017 January 21, from twelve telescopes at ten different observatories. The instruments and the main features of each station are listed in Table 1.As detailed in Methods (see also Fig. 1), the light curves (the normalized flux from the star plus Haumea versus time) show deep 1 2

To investigate the origin of the features discovered in the exoplanet population, the knowledge of exoplanets' mass and radius with a good precision ( 10 %) is essential. To achieve this purpose the discovery of transiting exoplanets around bright stars is of prime interest. In this paper, we report the discovery of three transiting exoplanets by the SuperWASP survey and the SOPHIE spectrograph with mass and radius determined with a precision better than 15 %. WASP-151b and WASP-153b are two hot Saturns with masses, radii, densities and equilibrium temperatures of 0.31 +0.04 −0.03 M J , 1.13 +0.03 −0.03 R J , 0.22 +0.03 −0.02 ρ J and 1, 290 +20 −10 K, and 0.39 +0.02 −0.02 M J , 1.55 +0.10 −0.08 R J , 0.11 +0.02 −0.02 ρ J and 1, 700 +40 −40 K, respectively. Their host stars are early G type stars (with magV ∼ 13) and their orbital periods are 4.53 and 3.33 days, respectively. WASP-156b is a Super-Neptune orbiting a K type star (magV = 11.6) . It has a mass of 0.128 +0.010 −0.009 M J , a radius of 0.51 +0.02 −0.02 R J , a density of 1.0 +0.1 −0.1 ρ J , an equilibrium temperature of 970 +30 −20 K and an orbital period of 3.83 days. The radius of WASP-151b appears to be only slightly inflated, while WASP-153b presents a significant radius anomaly compared to the model of Baraffe et al. (2008). WASP-156b, being one of the few well characterised Super-Neptunes, will help to constrain the still debated formation of Neptune size planets and the transition between gas and ice giants. The estimates of the age of these three stars confirms an already observed tendency for some stars to have gyrochronological ages significantly lower than their isochronal ages. We propose that high eccentricity migration could partially explain this behaviour for stars hosting a short period planet. Finally, these three planets also lie close to (WASP-151b and WASP-153b) or below (WASP-156b) the upper boundary of the Neptunian desert. Their characteristics support that the ultra-violet irradiation plays an important role in this depletion of planets observed in the exoplanet population.

Four mosaics of deep, continuum‐subtracted, CCD images have been obtained over the extensive Galactic radio continuum shell, W50, which surrounds the remarkable stellar system SS 433. Two of these mosaics in the and [O iii] 5007 Å emission lines, respectively, cover a field of which contains all of W50 but at a low angular resolution of 5 arcsec. The third and fourth mosaics cover the eastern (in [O iii] 5007 Å) and western (in 6548, 6584 Å) filamentary nebulosity, respectively, but at an angular resolution of 1 arcsec. These observations are supplemented by new low‐dispersion spectra and long‐slit, spatially resolved echelle spectra. The [O iii] 5007 Å images show for the first time the distribution of this emission in both the eastern and western filaments while new emission features are also found in both of these regions. Approaching flows of faintly emitting material from the bright eastern filaments of up 100 km s−1 in radial velocity are detected. The present observations also suggest that the heliocentric systemic radial velocity of the whole system is 56 ± 2 km s−1. Furthermore, very deep imagery and high‐resolution spectroscopy of a small part of the northern radio ridge of W50 has revealed for the first time the very faint optical nebulosity associated with this edge. It is suggested that patchy foreground dust along the ≈5 kpc sightline is inhibiting the detection of all of the optical nebulosity associated with W50. The interaction of the microquasar jets of SS 433 with the W50 shell is discussed.

Aims. We present time-resolved photometry of five relatively poorly-studied cataclysmic variables: V1193 Ori, LQ Peg, LD 317, V795 Her, and MCT 2347-3144. Methods. The observations were made using four 1m-class telescopes for a total of more than 250 h of observation and almost 16 000 data points. For LQ Peg WHT spectroscopic data have been analysed as well. Results. The light curves show a wide range of variability on different time scales from minutes to months. We detect for the first time a brightness variation of 0.05 mag in amplitude in V1193 Ori on the same timescale as the orbital period, which we interpret as the result of the irradiation of the secondary. A 20-min quasi-periodic oscillation is also detected. The mean brightness of the system has changed by 0.5 mag on a three-month interval, while the flickering was halved. In LQ Peg a 0.05 mag modulation was revealed with a period of about 3 h. The flickering was much smaller, of the order of 0.025 mag. A possible quasi-periodic oscillation could exist near 30 min. For this object, the WHT spectra are single-peaked and do not show any radial-velocity variations. The data of LD 317 show a decrease in the mean magnitude of the system. No periodic signal was detected but this is certainly attributable to the very large flickering observed: between 0.07 and 0.1 mag. For V795 Her, the 2.8-h modulation, thought to be a superhump arising from the precession of the disc, is present. We show that this modulation is not stable in terms of periodicity, amplitude, and phase. Finally, for MCT 2347-3144, a clear modulation is seen in a first dataset obtained in October 2002. This modulation is absent in August 2003, when the system was brighter and showed much more flickering.