* Astronomy

Members Login
Post Info TOPIC: Comet 81P/Wild


L

Posts: 112091
Date:
RE: Comet 81P/Wild
Permalink  
 


Comet 81P/Wild is at Opposition (4.244 AU) on the 29th September 2013



__________________


L

Posts: 112091
Date:
Permalink  
 

Title: The origin of the 3.4 micron feature in Wild 2 cometary particles and in ultracarbonaceous interplanetary dust particles
Authors: Graciela Matrajt, George Flynn, Don Brownlee, Dave Joswiak, Sasa Bajt

We analysed 2 ultra-carbonaceous interplanetary dust particles and 2 cometary Wild 2 particles with infrared spectroscopy. We characterised the carrier of the 3.4 micron band in these samples and compared its profile and the CH2/CH3 ratios to the 3.4 micron band in the diffuse interstellar medium (DISM), in the insoluble organic matter (IOM) from 3 primitive meteorites, in asteroid 24 Themis and in the coma of comet 103P/Hartley 2. We found that the 3.4 micron band in both Wild 2 and IDPs is similar, but different from all the other astrophysical environments that we compared to. The 3.4 micron band in IDPs and Wild 2 particles is dominated by CH2 groups, the peaks are narrower and stronger than in the meteorites, asteroid Themis, and the DISM. Also, the presence of the carbonyl group C=O at 1700 cm-1 (5.8 micron) in most of the spectra of our samples, indicates that these aliphatic chains have O bonded to them, which is quite different from astronomical spectra of the DISM. Based on all these observations we conclude that the origin of the carrier of the 3.4 micron band in IDPs and Wild 2 samples is not interstellar, instead, we suggest that the origin lies in the outermost parts of the solar nebula.

Read more (1459kb, PDF)



__________________


L

Posts: 112091
Date:
Permalink  
 

Comet Wild2: First Evidence of Space Weathering

The traditional picture of comets as cold, icy, unchanging bodies throughout their history is being reappraised in the light of analyses of dust grains from Comet Wild2. A team led by the University of Leicester has detected the presence of iron in a dust grain, evidence of space weathering that could explain the rusty reddish colour of Wild2's outer surface. The results will be presented by Dr John Bridges at the National Astronomy Meeting in Manchester on Tuesday 27th March.
Read more 



__________________


L

Posts: 112091
Date:
Permalink  
 

UH scientists analyse comet grain to estimate age of Jupiter

Jupiter ploughs through the solar system like a giant vacuum cleaner, sucking up rocks and dust with its massive gravity.
That's been going on for about 4.565 billion years, University of Hawaii scientists reckon by studying a grain of comet dust.
Particles from Comet Wild 2 were brought back to Earth by NASA's Stardust spacecraft in 2006. One was a fragment formed by high-temperature processes in the cloud that surrounded the sun in its infancy.

Read more 



__________________


L

Posts: 112091
Date:
Permalink  
 

Title: Incorporation of a Late-forming Chondrule into Comet Wild 2
Authors: R. C. Ogliore, G. R. Huss, K. Nagashima, A. L. Butterworth, Z. Gainsforth, J. Stodolna, A. J. Westphal, D. Joswiak, T. Tyliszczak

We report the petrology, O isotopic composition, and Al-Mg isotope systematics of a chondrule fragment from the Jupiter-family comet Wild 2, returned to Earth by NASA's Stardust mission. This object shows characteristics of a type II chondrule that formed from an evolved oxygen isotopic reservoir. No evidence for extinct 26Al was found, with (26Al/ 27Al)0 < 3.0 x 10^-6. Assuming homogenous distribution of 26Al in the solar nebula, this particle crystallised at least 3 Myr after the earliest solar system objects-relatively late compared to most chondrules in meteorites. We interpret the presence of this object in a Kuiper Belt body as evidence of late, large-scale transport of small objects between the inner and outer solar nebula. Our observations constrain the formation of Jupiter (a barrier to outward transport if it formed further from the Sun than this cometary chondrule) to be more than 3 Myr after CAIs.

Read more (6606kb, PDF)



__________________


L

Posts: 112091
Date:
Permalink  
 

Shooting Iron Sulphides into Aluminium Foil to Better Understand Comet Wild 2

When NASA's Stardust mission returned samples from comet 81P/Wild 2 to Earth in 2006, researchers found particles in the aerogel collector-cells as well as in the aluminium (Al) foil, which wrapped the cells and facilitated the safe removal of the aerogel from the collector frame. These Al-foil pull tabs, though not the primary collecting material, captured a bonus assortment of cometary grains. But did the impacts into the Al foil change the Wild 2 grains? Teams of scientists have been hard at work in the laboratory to answer that question by simulating impacts into Stardust Al foil using a light gas gun to shoot powders of the major minerals found in cometary dust.
They are studying the impact craters on the Al foils and what's left of the impacting particles, the residues, that coat the crater surfaces. Whether or not the original chemical composition of the impacting particle is preserved in the residue is a key question to examine in the laboratory, as the answer bears on how accurately the researchers can determine the original chemistry of the cometary grains from Wild 2.

Read more



__________________


L

Posts: 112091
Date:
Permalink  
 

Frozen Comet Had a Watery Past, UA Scientists Find

The discovery of minerals requiring liquid water for their formation challenges the paradigm of comets as "dirty snowballs" frozen in time.
For the first time, scientists have found convincing evidence for the presence of liquid water in a comet, shattering the current paradigm that comets never get warm enough to melt the ice that makes up the bulk of their material.

Read more 



__________________


L

Posts: 112091
Date:
Permalink  
 

The magnitude 13.9 comet 81P/Wild 2 will pass 0.32° from the magnitude 11.5 galaxy NGC 5878, in the constellation Libra, at 23:00 UT, 7th August, 2010.

__________________


L

Posts: 112091
Date:
Permalink  
 

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.

Read more (267kb. PDF)

__________________


L

Posts: 112091
Date:
Comet Wild 2
Permalink  
 


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.

Read more

__________________
1 2  >  Last»  | Page of 2  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard