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Post Info TOPIC: Comet 81P/Wild


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RE: Comet 81P/Wild
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Title: Water production in comet 81P/Wild 2 as determined by Herschel/HIFI
Authors: M. de Val-Borro, P. Hartogh, J. Crovisier, D. Bockelée-Morvan, N. Biver, D. C. Lis, R. Moreno, C. Jarchow, M. Rengel, S. Szutowicz, M. Banaszkiewicz, F. Bensch, M. I. Blecka, M. Emprechtinger, T. Encrenaz, E. Jehin, M. Küppers, L.-M. Lara, E. Lellouch, B. M. Swinyard, B. Vandenbussche, E. A. Bergin, G. A. Blake, J. A. D. L. Blommaert, J. Cernicharo, L. Decin, P. Encrenaz, T. de Graauw, D. Hutsemékers, M. Kidger, J. Manfroid, A. S. Medvedev, D. A. Naylor, R. Schieder, D. Stam, N. Thomas, C. Waelkens, R. Szczerba, P. Saraceno, A. M. Di Giorgio, S. Philipp, T. Klein, V. Ossenkopf, P. Zaal, R. Shipman

The high spectral resolution and sensitivity of Herschel/HIFI allows for the detection of multiple rotational water lines and accurate determinations of water production rates in comets. In this letter we present HIFI observations of the fundamental 110-101 (557 GHz) ortho and 111-000 (1113 GHz) para rotational transitions of water in comet 81P/Wild 2 acquired in February 2010. We mapped the extent of the water line emission with five point scans. Line profiles are computed using excitation models which include excitation by collisions with electrons and neutrals and solar infrared radiation. We derive a mean water production rate of 1.0 x 10^{28} molecules s^{-1} at a heliocentric distance of 1.61 AU about 20 days before perihelion, in agreement with production rates measured from the ground using observations of the 18-cm OH lines. Furthermore, we constrain the electron density profile and gas kinetic temperature, and estimate the coma expansion velocity by fitting the water line shapes.

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Comet Wild 2
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Scientists put the Comet Wild 2 under the microscope

Researchers at the University of Leicester are examining extraterrestrial material from a comet to assess the origins of our Solar System.
For the first time ever, material samples from a comet were collected in the Stardust Mission. It was the first mission since the Apollo landings to have successfully returned extraterrestrial material for scientists to study in the laboratory. At the University of Leicester's Space Research Centre and at Diamond Light Source, the UK's national synchrotron facility - a series of super microscopes - scientists are currently finding out what a comet is really made of.
The Stardust probe travelled 3.2 billion km in space, and flew through the coma of Comet Wild2 collecting tiny grains of dust, returning them back to Earth in 2006. They are being dissected at NASA and the University of California and being sent to a few laboratories around the world, with the University of Leicester being one of them.
By developing micro manipulation techniques, researchers at the University of Leicester have further dissected the tiny samples to study the comet to atomic precision under a Transmission Electron Microscope. This 'post-mortem' of Comet Wild2 has revealed for the first time the true composition of a comet.

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Comet 81P/Wild 2 makes its closest approach to the Earth (0.673 AU) on the 5th April, 2010.

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Wild2.jpg

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Comet 81P/Wild 2
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Though comets are thought to be some of the oldest, most primitive bodies in the solar system, new research on comet Wild 2 indicates that inner solar system material was transported to the comet-forming region at least 1.7 million years after the formation of the oldest solar system solids.
The research by Lawrence Livermore National Laboratory scientists and colleagues provides the first constraint on the age of cometary material from a known comet. The findings are published in the Feb. 25 edition of Science Express.
The NASA Stardust mission to comet Wild 2, which launched in 1999, was designed around the premise that comets preserve pristine remnants of materials that helped form the solar system. In 2006, Stardust returned with the first samples from a comet.

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RE: Comet 81P/Wild
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The magnitude 9.5 comet 81/P Wild is 0.75 degree from the magnitude 11.7 galaxy NGC 5324 in the constellation Virgo, at 22:00 UT, 23rd February, 2010.

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Comet 81P/Wild 2 is at perihelion (1.598 AU)

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Comet 81P/Wild 2
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Ephemeris
Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase   mag
2010 02 03 13 18.27 -05 15.8 0.936 1.610 113.8 34.1 10.0
2010 02 08 13 27.26 -05 46.3 0.899 1.605 116.6 33.3 9.8
2010 02 13 13 35.70 -06 11.6 0.864 1.601 119.5 32.4 9.7
2010 02 18 13 43.49 -06 31.4 0.832 1.599 122.6 31.4 9.7
2010 02 23 13 50.57 -06 45.8 0.802 1.598 125.9 30.1 9.6
2010 02 28 13 56.86 -06 54.6 0.775 1.599 129.4 28.6 9.5


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Comet 81P/Wild 2 (magnitude 10.1) will pass close to the galaxy NGC 4684 at 1:00 UT, 18th January, 2010.
The comet will only be 0.43° from the center of the galaxy (magnitude 12.4).

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The 10th magnitude comet 81/P Wild is 1 degree from the planet Saturn in the constellation Virgo.

81pwild-2010-1-2-11h19b.gif
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Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase   mag  mag

2009 12 30 12 06.04 +00 09.6 1.257 1.687 97.0 35.3 10.9 20.1
2010 01 04 12 16.96 -00 45.9 1.205 1.672 99.2 35.5 10.8 20.0
2010 01 09 12 27.77 -01 39.2 1.155 1.658 101.4 35.5 10.6 19.9
2010 01 14 12 38.40 -02 29.8 1.106 1.646 103.8 35.5 10.5 19.8
2010 01 19 12 48.83 -03 17.1 1.061 1.635 106.1 35.3 10.3 19.6
2010 01 24 12 58.98 -04 00.9 1.017 1.625 108.6 35.0 10.2 19.5
2010 01 29 13 08.82 -04 40.6 0.975 1.617 111.2 34.6 10.1 19.4


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