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TOPIC: eta Corvi
Blobrana


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Title: Spitzer Evidence for a Late Heavy Bombardment and the Formation of Urelites in Corvi at ~1 Gyr
Authors: C. M. Lisse, M. C. Wyatt, C. H. Chen, A. Morlok, D. M. Watson, P. Manoj, P. Sheehan, T. M. Currie, P. Thebault, M. L. Sitko

We have analysed Spitzer and NASA/IRTF 2 - 35 \mum spectra of the warm, ~350 K circumstellar dust around the nearby MS star {\eta} Corvi (F2V, 1.4 \pm 0.3 Gyr). The spectra show clear evidence for warm, water- and carbon-rich dust at ~3 AU from the central star, in the system's Terrestrial Habitability Zone. Spectral features due to ultra-primitive cometary material were found, in addition to features due to impact produced silica and high temperature carbonaceous phases. At least 9 x 10^18 kg of 0.1 - 100 \mum warm dust is present in a collisional equilibrium distribution with dn/da ~ a^-3.5, the equivalent of a 130 km radius KBO of 1.0 g/cm^3 density and similar to recent estimates of the mass delivered to the Earth at 0.6 - 0.8 Gyr during the Late Heavy Bombardment. We conclude that the parent body was a Kuiper-Belt body or bodies which captured a large amount of early primitive material in the first Myrs of the system's lifetime and preserved it in deep freeze at ~150 AU. At ~1.4 Gyr they were prompted by dynamical stirring of their parent Kuiper Belt into spiralling into the inner system, eventually colliding at 5-10 km/sec with a rocky planetary body of mass \leq MEarth at ~3 AU, delivering large amounts of water (>0.1% of MEarth's Oceans) and carbon-rich material. The Spitzer spectrum also closely matches spectra reported for the Ureilite meteorites of the Sudan Almahata Sitta fall in 2008, suggesting that one of the Ureilite parent bodies was a KBO.

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Blobrana


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Comets may be creating oceans on alien planet

Comets have been caught battering an exoplanet for the first time, new observations suggest. If the existence of the planet is confirmed, the finding means that the impacts are bringing water and organic material - the essential ingredients for life - to a world that lies in the habitable zone around its star.
The cometary shower is taking place around a bright star about 60 light years away called Eta Corvi, which is visible to the naked eye in the northern sky.
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Blobrana


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NASA's Spitzer Detects Comet Storm in Nearby Solar System

NASA's Spitzer Space Telescope has detected signs of icy bodies raining down in an alien solar system. The downpour resembles our own solar system several billion years ago during a period known as the "Late Heavy Bombardment," which may have brought water and other life-forming ingredients to Earth.
During this epoch, comets and other frosty objects that were flung from the outer solar system pummelled the inner planets. The barrage scarred our moon and produced large amounts of dust.
Now Spitzer has spotted a band of dust around a nearby bright star in the northern sky called Eta Corvi that strongly matches the contents of an obliterated giant comet. This dust is located close enough to Eta Corvi that Earth-like worlds could exist, suggesting a collision took place between a planet and one or more comets. The Eta Corvi system is approximately one billion years old, which researchers think is about the right age for such a hailstorm.
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Title: Sub-millimetre images of a dusty Kuiper belt around eta Corvi
Authors: Wyatt, M. C.; Greaves, J. S.; Dent, W. R. F.; Coulson, I. M.

We present submillimetre and mid-IR images of the circumstellar disk around the nearby F2 V star Corvi. The disk is resolved at 850 m with a size of ~100 AU. At 450 m the emission is found to be extended at all position angles, with significant elongation along a position angle of 130deg±10deg at the highest resolution (9.3"), this emission is resolved into two peaks that are within the uncertainties offset symmetrically from the star at 100 AU projected separation. Modelling the appearance of emission from a narrow ring in the submillimetre images shows that the observed structure cannot be caused by an edge-on or face-on axisymmetric ring; the observations are consistent with a ring of radius 150±20 AU seen at 45deg±25deg inclination. More face-on orientations are possible if the dust distribution includes two clumps similar to Vega; we show how such a clumpy structure could arise from the migration over 25 Myr of a Neptune mass planet from 80 to 105 AU. The inner 100 AU of the system appears relatively empty of submillimetre-emitting dust, indicating that this region may have been cleared by the formation of planets, but the disk emission spectrum shows that IRAS detected an additional hot component with a characteristic temperature of 370±60 K (implying a distance of 1-2 AU). At 11.9 m we found the emission to be unresolved, with no background sources that could be contaminating the fluxes measured by IRAS. The age of this star is estimated to be ~1 Gyr. It is very unusual for such an old main-sequence star to exhibit significant mid-IR emission. The proximity of this source makes it a perfect candidate for further study from optical to millimetre wavelengths to determine the distribution of its dust.

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