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Topic: Coma cometary


  
  comet coma comet coma comet coma comet coma
The gas coma consists of molecules liberated from the nucleus by solar heating and sublimation.
The outflow speed of the coma is comparable to the speed of sound in the coma gas at the temperature of the nucleus.
The dust coma consists of dust grains dragged from the nucleus by the rush of sublimating gas.
www.ifa.hawaii.edu /faculty/jewitt/coma.html   (0 words)

  
 Giotto Information
The scientific payload was comprised of ten hardware experiments: a narrow-angle camera, three mass spectrometers for neutrals, ions and dust, various dust detectors, a photopolarimeter and a set of plasma experiments.
All experiments performed well and returned a wealth of new scientific results, of which perhaps the most important was the clear identification of the cometary nucleus.
The Johnstone Plasma Analyser detected the first presence of cometary ions 600,000 km from the nucleus at 12 hours before the closest approach.
nssdc.gsfc.nasa.gov /planetary/giotto.html   (523 words)

  
 Coma (cometary)
It is formed when the comet passes close to the sun on its highly elliptical orbit; as the comet warms, parts of it melt and/or vaporize.
The coma is generally made of ice and dust.
Larger dust particles are left along the comet's orbital path while smaller particles are pushed away from the Sun into the comet's tail by light pressure [1].
en.explicatus.org /wiki/Coma_(cometary)   (120 words)

  
 coma
A glowing envelope of gas and dust that surrounds a comet’s nucleus when the comet comes within a few astronomical units of the Sun (although Chiron has been seen to develop a coma at 11 AU).
At perihelion, the coma is typically about 100,000 km across, and shaped into a teardrop by the solar wind.
Together, the coma and the nucleus form the comet’s head.
www.daviddarling.info /encyclopedia/C/coma.html   (135 words)

  
 The STARDUST Science
Cometary samples are of intrinsic interest for the entire comet science community, but hold considerable interest for the exobiologists as well.
Samples of cometary volatiles are captured in three forms: entrapped within dust particles, chemisorped by dopands within selected capture medium and physisorbted on the large surface area of the capture medium.
Originally the captured dust was to be tagged and cometary dust dynamics to be studied using an acoustic sensor mounted in the base of the capture media to register both time and location of the dust capture nondestructively.
stardust.jpl.nasa.gov /science/sci.html   (11406 words)

  
 Comets
The coma, which produces the nebulous appearance of the cometary head, is a short-lived, rarefied, and dusty atmosphere escaping from the nucleus.
The discrete emission of light by cometary atoms, radicals, or ions is due to the selective absorption of sunlight followed by its reemission either at the same wavelength (resonance) or at a different wavelength (fluorescence).
An early cometary bombardment of the Earth, predicted in some accretion models of the solar system, may have brought the oceans and the atmosphere, as well as a veneer of the molecules needed for life to develop on the Earth.
www.geocities.com /zlipanov/comets/comets.html   (10543 words)

  
 Cosmos: The SAO Encyclopedia: cometary tails
As a comet approaches the Sun, it is heated, releasing gas and dust into a temporary atmosphere (called the coma) around the nucleus of the comet.
It is the interaction of photons of sunlight and the solar wind with this coma that produces the long cometary tails we normally associate with this type of celestial object.
This neutral tail consists of neutral sodium atoms thought to be released by dust particles in both the coma and the dust tail.
cosmos.swin.edu.au /entries/cometarytails/cometarytails.html   (205 words)

  
 Matthew Senay Graduate Brochure Page
The primary sources of radio emission from comets are continuum radiation from dust in the cometary coma and spectral line emission from various species of molecules produced by the sublimation of volatile ices in the nucleus.
Dust is entrained by the outgassing of these volatile ices and is ejected from the nucles to form the coma we are accustomed to viewing at optical wavelengths.
This is observational evidence against models of the nucleus with a warm interior, hypothetically sustained by the exothermic phase change of a type of water ice that has not been observed to exist in comets.
www-astro.phast.umass.edu /directory/people/senay.html   (671 words)

  
 Coma (cometary)   (Site not responding. Last check: )
In astronomy, the nebulous envelope around the nucleus of a comet is called its coma (from the Latin word for "hair").
It is formed when the comet passes close to the sun on its highly elliptical orbit; as the comet warms, parts of it melt and/or vaporize and trail behind the comet.
The coma is generally made of ice and dust.
www.xasa.com /wiki/en/wikipedia/c/co/coma__cometary_.html   (100 words)

  
 Comets/ Asteroids and Comets Section
In addition, the long-slit spectra allow dissociation rates of the cometary parent and daughter molecules to be verified, even at large heliocentric distances where they are poorly known, and the excitation mechanism of the cometary daughter species to be studied.
A problem of cometary physics which has attracted much attention in recent years is the possible existence and evolution of a cloud of large particles (mm- to m- sized) around cometary nuclei.
Further environmental constraints relevant for landing and operating instruments on a cometary nucleus are presented, such as sublimation and re-condensation of water on the cold parts of the lander and varying illumination conditions over the extent of the mission.
solarsystem.dlr.de /KK/comets.shtml   (1990 words)

  
 Subaru Telescope, NAOJ
Comet Hale-Bopp was the first example of the detection of water icy grains in a cometary coma, and this time is the second one.
Cometary nuclei are thought to be remnants of planetary sources (called planetecimals) existed in the early solar system.
Since it is considered that the cometary nuclei were formed from icy dust (nonvolatile dust covered with ice mantle) in the interstellar medium or the solar nebula, research into such water icy grains in the cometary nuclei is very important to reveal the physical conditions of the early solar system.
www.naoj.org /Pressrelease/2004/04/04/index.html   (511 words)

  
 Comet Introduction
The coma and the nucleus together constitute the head of the comet.
A small star cluster (C0736-105, or Melotte 72) is visible in the lower right of the image, between the head of the comet and the bright red star in the lower-right corner.
A second possible explanation is that the X-rays are produced from the violent collision between the comet material and the supersonic "wind" of plasma and particles streaming away from the Sun.
www.solarviews.com /eng/comet.htm   (0 words)

  
 Reflections on the “Deep Impact” Anniversary
Cometary nuclei did not condense from a cold diffuse cloud in isolation, but were part of a rocky body before these pieces were accelerated into space to become comets.
Certain cometary spectral features have been noted in the past that imply "intense electric fields in the coma." The vaporized copper projectile would add greatly to the plasma conductivity at the point of impact so that most of the comet discharge activity would suddenly be concentrated there for a short time.
Negative cometary ions have been discovered close to comet nuclei and are a puzzle for comet theorists because the ions are easily destroyed by solar radiation.
www.thunderbolts.info /webnews/deep_impact_reflections.htm   (4439 words)

  
 APOD: Glossary
coma: A spherical cloud of material surrounding the head of a comet.
A cometary coma can extend up to a million miles from the nucleus.
Comet comas can extend up to a million miles from the nucleus and comet tails can be millions of miles long.
antwrp.gsfc.nasa.gov /apod/lib/glossary.html   (0 words)

  
 [12.02] The HNC/HCN Ratio in Comets C/2000 WM1 (LINEAR) and C/2002 C1 (Ikeya-Zhang)   (Site not responding. Last check: )
The discovery of cometary HNC in comet C/1996 B2 (Hyakutake) thus seemed to provide evidence for the survival of interstellar ices in comets.
Subsequent data for comet C/1997 O1 (Hale-Bopp) showed, however, a dependence of the HNC/HCN ratio on heliocentric distance that indicated that most HNC in that comet was produced in the cometary coma, rather than being a constituent of the comet's nucleus.
Cometary HNC may be a photodissociation product of organic grains or large organic polymers stored in the nucleus.
www.aas.org /publications/baas/v34n3/dps2002/39.htm   (336 words)

  
 Comet Hale-Bopp (C/1995 O1) : Johns Hopkins University
The image to the left is from a 300 second exposure and shows how the ``pinwheel'' structure of the cometary coma clearly distinguishes Hale-Bopp from the numerous stars in the field (at the time of these images the comet was passing near the galactic plane in the constellation Sagittarius).
Fortunately, cometary comae are usually optically thin which means that, in principle, the nucleus can be picked out provided that sufficient spatial resolution is used.
If the coma light distribution is "well-behaved", then one would have some confidence that the coma brightness was well-represented in the unresolved region, allowing an accurate nuclear brightness to be determined.
www.pha.jhu.edu /~weaver/Hale-Bopp.html   (2997 words)

  
 Comets
The supposed nucleus of the comet is the bright centre of the coma.
The action of the Sun's radiation and the magnetic field associated with the Solar wind remove gas and dust from the coma and it is 'blown' away to form the comet's tail.
The dust which is blown away from the coma, is blown by the Sun's radiation and it moves in a direction which is governed by the motion of the comet, by the size of the dust particles, and by the speed of ejection from the coma.
www.oarval.org /section3_15.htm   (1307 words)

  
 ADS Abstract Service
We discuss the properties of the nucleus and inner coma of Comet Hale-Bopp (C/1995 O1) as derived from observations of its occultation of Star PPM 200723 on 5 October 1996, while the comet was 2.83 AU from the Sun.
The dependence of the dust coma's opacity on cometocentric distance, rho, was steeper than expected for force-free, radial flow, being probably as steep as or steeper than 1/rho^1.4 within 100 km of the nucleus (though it is marginally possible to fit one coma hemisphere with a 1/rho law).
Assuming the dust coma flowed radially from a spot at the center of the nucleus and that the coma's profile was not any steeper than rho^-2, the upper limit to the radius of the nucleus is about 30 km, though relaxing these assumptions limits the radius to 48 km.
www.astro.umd.edu /~lisse/1999DPS....31.5506L.html   (6009 words)

  
 Universe Today - Following the Dust Trail
Giotto's mission was obtain color photographs of the nucleus, determine the elemental and isotopic composition of volatile components in the cometary coma, study the parent molecules, and help us to understand the physical and chemical processes that occur in the cometary atmosphere and ionosphere.
This type of analysis showed that cometary materials are generally a mixture of silicates and carbon in amorphous and crystalline structure formed in the matrix.
A single cometary particle could be a composite of millions of individual interstellar dust grains, allowing us new insight on galactic and nebular processes increasing our understanding of both comets and stars.
www.universetoday.com /am/publish/following_dust_trail.html   (2595 words)

  
 The relation of temporal variations of soft X-ray emission from comet Hyakutake to variations of ion fluxes in the ...
The correlation between the solar wind oxygen flux and cometary X rays degrades with increasing latitudinal separation of SOHO from the comet.
Cometary X-ray emission is not sensitive to variations in solar X-ray fluxes and is unlikely to be caused by crossing of the heliospheric current sheet.
Cometary X rays have some shortcomings as remote sensors of the solar wind, however, because of variations in cometary gas production rates and in the charge states and abundances of heavy solar wind ions.
www.agu.org /pubs/crossref/2000/1999JA000299.shtml   (430 words)

  
 CCD Photometry of Comets
Furthermore, many professional astronomers who concentrate on cometary photometry tend to use small 'diaphram' sizes to obtain the brightness of only the inner coma [e.g., Jewitt 1991] --- and indeed with large coma diameters, it may be impossible to integrate the entire brightness with a telescopic CCD camera.
The coma should always be small enough in comparison with the field-of-view (FOV) to have a lot of pixels far from the comet available for proper derivation of the background level.
For comets with coma diameters approximately 5' or greater, the observer with a small FOV cannot decide reliably where the apparent coma ends and cannot be sure that the pixels around the coma do really represent the background level.
cfa-www.harvard.edu /icq/CCDmags.html   (7641 words)

  
 The Explosive Demise of Comet Linear
In fact, the excess of electrons in a cometary coma was first noted in 1986, when the Giotto spacecraft detected an abundance of negatively charged atoms in the inner coma of Comet Halley.
Juergens proposed an electric Sun model, along with the corollary that cometary comas and tails are produced by an electrical exchange between the Sun and the comet.
As the comet neared its perihelion or closest approach to the Sun"about 114 million kilometers (70 million miles) from the Sun, or three quarters of the distance from the Sun to Earth"astronomer Mark Kidger was observing Linear with the Jacobus Kapteyn Telescope at La Palma in the Canary Islands.
www.rense.com /general65/e3l.htm   (1606 words)

  
 Astronomical Astronomy Glossary Dictionary Terminology meanings
Coma (i) The matter surrounding the nucleus of a comet — it results from the evaporation of the nucleus.
Both the diffuseness (generally called a coma) and the tail are composed of gas and/or dust of various atomic or molecular compositions, as is ascertained by spectroscopy.
The coma and tail material come from a much smaller nucleus that is usually invisible due to the bright surrounding coma activity.
www.aoe.com.au /astronomical_glossary.html   (6593 words)

  
 The Dispatch - Serving the Lexington, NC - News   (Site not responding. Last check: )
It is formed when the comet passes close to the sun on its highly elliptical orbit; as the comet warms, parts of it melt and/or vaporize.
Larger dust particles are left along the comet's orbital path while smaller particles are pushed away from the Sun into the comet's tail by light pressure [1].
Stardust was a NASA mission to recover samples of a comet's coma.
www.the-dispatch.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=Coma_(cometary)   (140 words)

  
 SPRL 1995: Cometary Atmospheres   (Site not responding. Last check: )
The study of cometary atmospheres and ionospheres has advanced in recent years, so that the modeling of various atmospheric phenomena, which is required for data analysis, involves large-scale multi-dimensional gas-dynamic, gas-kinetic, and magnetohydrodynamic models.
The pumping effect of the coma dynamics is caused by the variable photochemical heating efficiency which requires a fully kinetic time-dependent model to understand.
A new kinetic model for the cometary coma has been developed at SPRL based on Direct Simulation Monte Carlo (DSMC) techniques originally developed in the field of computational fluid dynamics for studying non-equilibrium gas flows such as shock structures.
www.sprl.umich.edu /SPRL/research/comet_atmos.html   (584 words)

  
 HubbleSite - NewsCenter - Hubble Investigates Comet on a Collision Course with Jupiter (10/18/1993) - Release Text
A cometary origin would be likely if the coma is continually replenished by gas streaming off the fragments, since comets are more icy than asteroids.
The current Hubble image shows that the coma is apparently not continually being replenished, but more observations are needed to monitor the coma development further.
For example, on June 30, 1908 a 160-foot (50-meter) wide cometary nucleus or stony meteor is suspected to have disintegrated in Earth's atmosphere at an altitude of five miles (8 km).
hubblesite.org /newscenter/archive/releases/1993/22/text   (1251 words)

  
 JAC Style guide: template
In fact, the first detection of molecules in the coma (the J=4-3 rotational transition of HCN) was made already on February 10 at the JCMT.
We were able to obtain both continuum spectra of the emission from the dust in the coma at wavelengths from 2 mm to 350 microns, as well as simple maps at 800 microns wavelength of its distribution at a time just before close approach.
For comparison we obtained crude maps of the distribution of gas in the coma, using the HCN 4-3 transition.
www.jach.hawaii.edu /JCMT/publications/newsletter/n7/sci9.html   (1721 words)

  
 Space Studies Board
Bulk analyses of both collected coma dust and in-place solids on the cometary crust are critical elements in the CRAF plan because of the possibility of chemical fractionation between the cometary surface and the active gas-producing regions; inactive regions observed on the Halley surface could be thick lag deposits of devolatilized material.
These are essential data for comparison of cometary and meteoritic organic species, and of chemical evolutionary processes in the two environments.
Composition of parent organic molecules in coma gas is an important objective of the NIMS measurements.
www7.nationalacademies.org /ssb/craf87.html   (1684 words)

  
 The Dispatch - Serving the Lexington, NC - News   (Site not responding. Last check: )
Although it was initially classified as an asteroid, later dispute arose as to whether it was an asteroid or actually a comet.
At the time of its discovery, Chiron was close to aphelion, whereas the observations showing a coma were done closer to perihelion, perhaps explaining why no cometary behavior had been seen earlier.
As of March 2006, only one has been observed to have a cometary coma: 60558 Echeclus, which now also has the cometary designation 174P/Echeclus.
www.the-dispatch.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=2060_Chiron   (478 words)

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