* Astronomy

Title: Millimeter Imaging of the beta Pictoris Debris Disk: Evidence for a Planetesimal Belt
Authors: David J. Wilner (1), Sean M. Andrews (1), A. Meredith Hughes (2) ((1) Harvard-Smithsonian Center for Astrophysics, (2) University of California, Berkeley)

We present observations at 1.3 millimetres wavelength of the beta Pictoris debris disk with beam size 4.3 x 2.6 arcsec (83 x 50 AU) from the Submillimeter Array. The emission shows two peaks separated by ~7 arsec along the disk plane, which we interpret as a highly inclined dust ring or belt. A simple model constrains the belt center to 94±8 AU, close to the prominent break in slope of the optical scattered light. We identify this region as the location as the main reservoir of dust producing planetesimals in the disk.

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Exoplanet Caught on the Move

For the first time, astronomers have been able to directly follow the motion of an exoplanet as it moves from one side of its host star to the other. The planet has the smallest orbit so far of all directly imaged exoplanets, lying almost as close to its parent star as Saturn is to the Sun. Scientists believe that it may have formed in a similar way to the giant planets in the Solar System. Because the star is so young, this discovery proves that gas giant planets can form within discs in only a few million years, a short time in cosmic terms.
Only 12 million years old, or less than three-thousandths of the age of the Sun, Beta Pictoris is 75% more massive than our parent star. It is located about 60 light-years away towards the constellation of Pictor (the Painter) and is one of the best-known examples of a star surrounded by a dusty debris disc. Earlier observations showed a warp of the disc, a secondary inclined disc and comets falling onto the star.
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Title: The Pictoris disk imaged by Herschel PACS and SPIRE
Authors: B.Vandenbussche, B. Sibthorpe, B. Acke, E. Pantin, G. Olofsson, C. Waelkens, C. Dominik, M. J. Barlow, J.A.D.L. Blommaert, J. Bouwman, A.Brandeker, M.Cohen, W. DeMeester, W.R. F.Dent, K. Exter, J.Di Francesco, M. Fridlund, W.K.Gear, A.M.Glauser, H. L.Gomez, J. S.Greaves, P. C.Hargrave, P.M.Harvey, Th.Henning, A.M.Heras, M.R.Hogerheijde, W. S.Holland, R.Huygen, R. J. Ivison, C. Jean, S. J. Leeks, T. L. Lim, R. Liseau, B.C. Matthews, D.A. Naylor, G. L. Pilbratt, E. T. Polehampton, S. Regibo, P. Royer, A. Sicilia-Aguilar, B.M. Swinyard, H. J.Walker, R.Wesson

We obtained Herschel PACS and SPIRE images of the thermal emission of the debris disk around the A5V star \beta Pic. The disk is well resolved in the PACS filters at 70, 100, and 160 {\mu}m. The surface brightness profiles between 70 and 160 {\mu}m show no significant asymmetries along the disk, and are compatible with 90% of the emission between 70 and 160 {\mu}m originating in a region closer than 200 AU to the star. Although only marginally resolving the debris disk, the maps obtained in the SPIRE 250 - 500 {\mu}m filters provide full-disk photometry, completing the SED over a few octaves in wavelength that had been previously inaccessible. The small far-infrared spectral index ({\beta} = 0.34) indicates that the grain size distribution in the inner disk (<200AU) is inconsistent with a local collisional equilibrium. The size distribution is either modified by non-equilibrium effects, or exhibits a wavy pattern, caused by an under-abundance of impactors which have been removed by radiation pressure.

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