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Post Info TOPIC: HR 4796A
Blobrana


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Title: STIS Imaging of the HR 4796A Circumstellar Debris Ring
Authors: G. Schneider, A. J. Weinberger, E. E. Becklin, J. H. Debes, B. A. Smith

We have obtained high spatial resolution imaging observations of the HR 4796A circumstellar debris dust ring using the broad optical response of the Hubble Space Telescope Imaging Spectrograph in coronagraphic mode. We use our visual wavelength observations to improve upon the earlier measured geometrical parameters of the ring-like disk. Two significant flux density asymmetries are noted: (1) preferential forward scattering by the disk grains and (2) an azimuthal surface brightness anisotropy about the morphological minor axis of the disk with corresponding differential ansal brightness. We find the debris ring offset from the location of the star by ~1.4 AU, a shift insufficient to explain the differing brightnesses of the NE and SW ansae simply by the 1/r^2 dimmunition of starlight. The STIS data also better quantify the radial confinement of the starlight-scattering circumstellar debris, to a characteristic region <14 AU in photometric half-width, with a significantly steeper inner truncation than outward falloff in radial surface brightness. The inferred spatial distribution of the disk grains is consistent with the possibility of one or more unseen co-orbital planetary-mass perturbers, and the colours of the disk grains are consistent with a collisionally evolved population of debris, possibly including ices reddened by radiation exposure to the central star.

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Blobrana


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Scientists have observed signs of the building blocks of life in a disc of red dust surrounding a distant star, HR 4796A, which is about 8 million years old.

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Blobrana


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Title: Complex Organic Materials in the Circumstellar Disk of HR 4796A
Authors: J.H. Debes, A.J. Weinberger, G. Schneider

We combine HST/NICMOS imaging photometry of the HR 4796A disk at previously unobserved wavelengths between 1.71-2.22\micron with reprocessed archival observations to produce a measure of the dust's scattering efficiency as a function of wavelength. The spectrum of the dust, synthesised from the seven photometric measures, is characterised by a steep red slope increasing from 0.5 \micron to 1.6 \micron followed by a flattening of the spectrum at wavelengths > 1.6 \micron. We fit the spectrum with a model population of dust grains made of tholins, materials comprised of complex organic materials seen throughout the outer parts of our Solar System. The presence of organic material around a star that may be in the later stages of giant planet formation implies that the basic building blocks for life may be common in planetary systems.

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Blobrana


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HR 4796A.kmz
Google Sky file (2kb, kmz)

-- Edited by Blobrana at 15:24, 2008-01-12

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Blobrana


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Astronomers at the Carnegie Institution have found the first indications of highly complex organic molecules in the disk of red dust surrounding a distant star. The eight-million-year-old star, known as HR 4796A, is inferred to be in the late stages of planet formation, suggesting that the basic building blocks of life may be common in planetary systems.
In a study published in the current Astrophysical Journal Letters, John Debes and Alycia Weinberger of the Carnegie Institutions Department of Terrestrial Magnetism with Glenn Schneider of the University of Arizona report observations of infrared light from HR 4796A using the Near-Infrared Multi-Object Spectrometer aboard the Hubble Space Telescope. The researchers found that the spectrum of visible and infrared light scattered by the stars dust disk looks very red, the colour produced by large organic carbon molecules called tholins. The spectrum does not match those of other red substances, such as iron oxide.

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RA: 12 36 01.07, Dec: -39 52 10.0

-- Edited by Blobrana at 02:40, 2008-01-04

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